build: move package sources from src/pkg to src

Preparation was in CL 134570043.
This CL contains only the effect of 'hg mv src/pkg/* src'.
For more about the move, see golang.org/s/go14nopkg.

24 files changed, 9264 insertions, 0 deletions

diff --git a/src/text/scanner/scanner.go b/src/text/scanner/scanner.go
new file mode 100644
index 000000000..5199ee4fc
--- /dev/null
+++ b/src/text/scanner/scanner.go
@@ -0,0 +1,693 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package scanner provides a scanner and tokenizer for UTF-8-encoded text.
+// It takes an io.Reader providing the source, which then can be tokenized
+// through repeated calls to the Scan function.  For compatibility with
+// existing tools, the NUL character is not allowed. If the first character
+// in the source is a UTF-8 encoded byte order mark (BOM), it is discarded.
+//
+// By default, a Scanner skips white space and Go comments and recognizes all
+// literals as defined by the Go language specification.  It may be
+// customized to recognize only a subset of those literals and to recognize
+// different identifier and white space characters.
+//
+// Basic usage pattern:
+//
+//	var s scanner.Scanner
+//	s.Init(src)
+//	tok := s.Scan()
+//	for tok != scanner.EOF {
+//		// do something with tok
+//		tok = s.Scan()
+//	}
+//
+package scanner
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"os"
+	"unicode"
+	"unicode/utf8"
+)
+
+// A source position is represented by a Position value.
+// A position is valid if Line > 0.
+type Position struct {
+	Filename string // filename, if any
+	Offset   int    // byte offset, starting at 0
+	Line     int    // line number, starting at 1
+	Column   int    // column number, starting at 1 (character count per line)
+}
+
+// IsValid returns true if the position is valid.
+func (pos *Position) IsValid() bool { return pos.Line > 0 }
+
+func (pos Position) String() string {
+	s := pos.Filename
+	if pos.IsValid() {
+		if s != "" {
+			s += ":"
+		}
+		s += fmt.Sprintf("%d:%d", pos.Line, pos.Column)
+	}
+	if s == "" {
+		s = "???"
+	}
+	return s
+}
+
+// Predefined mode bits to control recognition of tokens. For instance,
+// to configure a Scanner such that it only recognizes (Go) identifiers,
+// integers, and skips comments, set the Scanner's Mode field to:
+//
+//	ScanIdents | ScanInts | SkipComments
+//
+// With the exceptions of comments, which are skipped if SkipComments is
+// set, unrecognized tokens are not ignored. Instead, the scanner simply
+// returns the respective individual characters (or possibly sub-tokens).
+// For instance, if the mode is ScanIdents (not ScanStrings), the string
+// "foo" is scanned as the token sequence '"' Ident '"'.
+//
+const (
+	ScanIdents     = 1 << -Ident
+	ScanInts       = 1 << -Int
+	ScanFloats     = 1 << -Float // includes Ints
+	ScanChars      = 1 << -Char
+	ScanStrings    = 1 << -String
+	ScanRawStrings = 1 << -RawString
+	ScanComments   = 1 << -Comment
+	SkipComments   = 1 << -skipComment // if set with ScanComments, comments become white space
+	GoTokens       = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
+)
+
+// The result of Scan is one of the following tokens or a Unicode character.
+const (
+	EOF = -(iota + 1)
+	Ident
+	Int
+	Float
+	Char
+	String
+	RawString
+	Comment
+	skipComment
+)
+
+var tokenString = map[rune]string{
+	EOF:       "EOF",
+	Ident:     "Ident",
+	Int:       "Int",
+	Float:     "Float",
+	Char:      "Char",
+	String:    "String",
+	RawString: "RawString",
+	Comment:   "Comment",
+}
+
+// TokenString returns a printable string for a token or Unicode character.
+func TokenString(tok rune) string {
+	if s, found := tokenString[tok]; found {
+		return s
+	}
+	return fmt.Sprintf("%q", string(tok))
+}
+
+// GoWhitespace is the default value for the Scanner's Whitespace field.
+// Its value selects Go's white space characters.
+const GoWhitespace = 1<<'\t' | 1<<'\n' | 1<<'\r' | 1<<' '
+
+const bufLen = 1024 // at least utf8.UTFMax
+
+// A Scanner implements reading of Unicode characters and tokens from an io.Reader.
+type Scanner struct {
+	// Input
+	src io.Reader
+
+	// Source buffer
+	srcBuf [bufLen + 1]byte // +1 for sentinel for common case of s.next()
+	srcPos int              // reading position (srcBuf index)
+	srcEnd int              // source end (srcBuf index)
+
+	// Source position
+	srcBufOffset int // byte offset of srcBuf[0] in source
+	line         int // line count
+	column       int // character count
+	lastLineLen  int // length of last line in characters (for correct column reporting)
+	lastCharLen  int // length of last character in bytes
+
+	// Token text buffer
+	// Typically, token text is stored completely in srcBuf, but in general
+	// the token text's head may be buffered in tokBuf while the token text's
+	// tail is stored in srcBuf.
+	tokBuf bytes.Buffer // token text head that is not in srcBuf anymore
+	tokPos int          // token text tail position (srcBuf index); valid if >= 0
+	tokEnd int          // token text tail end (srcBuf index)
+
+	// One character look-ahead
+	ch rune // character before current srcPos
+
+	// Error is called for each error encountered. If no Error
+	// function is set, the error is reported to os.Stderr.
+	Error func(s *Scanner, msg string)
+
+	// ErrorCount is incremented by one for each error encountered.
+	ErrorCount int
+
+	// The Mode field controls which tokens are recognized. For instance,
+	// to recognize Ints, set the ScanInts bit in Mode. The field may be
+	// changed at any time.
+	Mode uint
+
+	// The Whitespace field controls which characters are recognized
+	// as white space. To recognize a character ch <= ' ' as white space,
+	// set the ch'th bit in Whitespace (the Scanner's behavior is undefined
+	// for values ch > ' '). The field may be changed at any time.
+	Whitespace uint64
+
+	// IsIdentRune is a predicate controlling the characters accepted
+	// as the ith rune in an identifier. The set of valid characters
+	// must not intersect with the set of white space characters.
+	// If no IsIdentRune function is set, regular Go identifiers are
+	// accepted instead. The field may be changed at any time.
+	IsIdentRune func(ch rune, i int) bool
+
+	// Start position of most recently scanned token; set by Scan.
+	// Calling Init or Next invalidates the position (Line == 0).
+	// The Filename field is always left untouched by the Scanner.
+	// If an error is reported (via Error) and Position is invalid,
+	// the scanner is not inside a token. Call Pos to obtain an error
+	// position in that case.
+	Position
+}
+
+// Init initializes a Scanner with a new source and returns s.
+// Error is set to nil, ErrorCount is set to 0, Mode is set to GoTokens,
+// and Whitespace is set to GoWhitespace.
+func (s *Scanner) Init(src io.Reader) *Scanner {
+	s.src = src
+
+	// initialize source buffer
+	// (the first call to next() will fill it by calling src.Read)
+	s.srcBuf[0] = utf8.RuneSelf // sentinel
+	s.srcPos = 0
+	s.srcEnd = 0
+
+	// initialize source position
+	s.srcBufOffset = 0
+	s.line = 1
+	s.column = 0
+	s.lastLineLen = 0
+	s.lastCharLen = 0
+
+	// initialize token text buffer
+	// (required for first call to next()).
+	s.tokPos = -1
+
+	// initialize one character look-ahead
+	s.ch = -1 // no char read yet
+
+	// initialize public fields
+	s.Error = nil
+	s.ErrorCount = 0
+	s.Mode = GoTokens
+	s.Whitespace = GoWhitespace
+	s.Line = 0 // invalidate token position
+
+	return s
+}
+
+// next reads and returns the next Unicode character. It is designed such
+// that only a minimal amount of work needs to be done in the common ASCII
+// case (one test to check for both ASCII and end-of-buffer, and one test
+// to check for newlines).
+func (s *Scanner) next() rune {
+	ch, width := rune(s.srcBuf[s.srcPos]), 1
+
+	if ch >= utf8.RuneSelf {
+		// uncommon case: not ASCII or not enough bytes
+		for s.srcPos+utf8.UTFMax > s.srcEnd && !utf8.FullRune(s.srcBuf[s.srcPos:s.srcEnd]) {
+			// not enough bytes: read some more, but first
+			// save away token text if any
+			if s.tokPos >= 0 {
+				s.tokBuf.Write(s.srcBuf[s.tokPos:s.srcPos])
+				s.tokPos = 0
+				// s.tokEnd is set by Scan()
+			}
+			// move unread bytes to beginning of buffer
+			copy(s.srcBuf[0:], s.srcBuf[s.srcPos:s.srcEnd])
+			s.srcBufOffset += s.srcPos
+			// read more bytes
+			// (an io.Reader must return io.EOF when it reaches
+			// the end of what it is reading - simply returning
+			// n == 0 will make this loop retry forever; but the
+			// error is in the reader implementation in that case)
+			i := s.srcEnd - s.srcPos
+			n, err := s.src.Read(s.srcBuf[i:bufLen])
+			s.srcPos = 0
+			s.srcEnd = i + n
+			s.srcBuf[s.srcEnd] = utf8.RuneSelf // sentinel
+			if err != nil {
+				if err != io.EOF {
+					s.error(err.Error())
+				}
+				if s.srcEnd == 0 {
+					if s.lastCharLen > 0 {
+						// previous character was not EOF
+						s.column++
+					}
+					s.lastCharLen = 0
+					return EOF
+				}
+				// If err == EOF, we won't be getting more
+				// bytes; break to avoid infinite loop. If
+				// err is something else, we don't know if
+				// we can get more bytes; thus also break.
+				break
+			}
+		}
+		// at least one byte
+		ch = rune(s.srcBuf[s.srcPos])
+		if ch >= utf8.RuneSelf {
+			// uncommon case: not ASCII
+			ch, width = utf8.DecodeRune(s.srcBuf[s.srcPos:s.srcEnd])
+			if ch == utf8.RuneError && width == 1 {
+				// advance for correct error position
+				s.srcPos += width
+				s.lastCharLen = width
+				s.column++
+				s.error("illegal UTF-8 encoding")
+				return ch
+			}
+		}
+	}
+
+	// advance
+	s.srcPos += width
+	s.lastCharLen = width
+	s.column++
+
+	// special situations
+	switch ch {
+	case 0:
+		// for compatibility with other tools
+		s.error("illegal character NUL")
+	case '\n':
+		s.line++
+		s.lastLineLen = s.column
+		s.column = 0
+	}
+
+	return ch
+}
+
+// Next reads and returns the next Unicode character.
+// It returns EOF at the end of the source. It reports
+// a read error by calling s.Error, if not nil; otherwise
+// it prints an error message to os.Stderr. Next does not
+// update the Scanner's Position field; use Pos() to
+// get the current position.
+func (s *Scanner) Next() rune {
+	s.tokPos = -1 // don't collect token text
+	s.Line = 0    // invalidate token position
+	ch := s.Peek()
+	s.ch = s.next()
+	return ch
+}
+
+// Peek returns the next Unicode character in the source without advancing
+// the scanner. It returns EOF if the scanner's position is at the last
+// character of the source.
+func (s *Scanner) Peek() rune {
+	if s.ch < 0 {
+		// this code is only run for the very first character
+		s.ch = s.next()
+		if s.ch == '\uFEFF' {
+			s.ch = s.next() // ignore BOM
+		}
+	}
+	return s.ch
+}
+
+func (s *Scanner) error(msg string) {
+	s.ErrorCount++
+	if s.Error != nil {
+		s.Error(s, msg)
+		return
+	}
+	pos := s.Position
+	if !pos.IsValid() {
+		pos = s.Pos()
+	}
+	fmt.Fprintf(os.Stderr, "%s: %s\n", pos, msg)
+}
+
+func (s *Scanner) isIdentRune(ch rune, i int) bool {
+	if s.IsIdentRune != nil {
+		return s.IsIdentRune(ch, i)
+	}
+	return ch == '_' || unicode.IsLetter(ch) || unicode.IsDigit(ch) && i > 0
+}
+
+func (s *Scanner) scanIdentifier() rune {
+	// we know the zero'th rune is OK; start scanning at the next one
+	ch := s.next()
+	for i := 1; s.isIdentRune(ch, i); i++ {
+		ch = s.next()
+	}
+	return ch
+}
+
+func digitVal(ch rune) int {
+	switch {
+	case '0' <= ch && ch <= '9':
+		return int(ch - '0')
+	case 'a' <= ch && ch <= 'f':
+		return int(ch - 'a' + 10)
+	case 'A' <= ch && ch <= 'F':
+		return int(ch - 'A' + 10)
+	}
+	return 16 // larger than any legal digit val
+}
+
+func isDecimal(ch rune) bool { return '0' <= ch && ch <= '9' }
+
+func (s *Scanner) scanMantissa(ch rune) rune {
+	for isDecimal(ch) {
+		ch = s.next()
+	}
+	return ch
+}
+
+func (s *Scanner) scanFraction(ch rune) rune {
+	if ch == '.' {
+		ch = s.scanMantissa(s.next())
+	}
+	return ch
+}
+
+func (s *Scanner) scanExponent(ch rune) rune {
+	if ch == 'e' || ch == 'E' {
+		ch = s.next()
+		if ch == '-' || ch == '+' {
+			ch = s.next()
+		}
+		ch = s.scanMantissa(ch)
+	}
+	return ch
+}
+
+func (s *Scanner) scanNumber(ch rune) (rune, rune) {
+	// isDecimal(ch)
+	if ch == '0' {
+		// int or float
+		ch = s.next()
+		if ch == 'x' || ch == 'X' {
+			// hexadecimal int
+			ch = s.next()
+			hasMantissa := false
+			for digitVal(ch) < 16 {
+				ch = s.next()
+				hasMantissa = true
+			}
+			if !hasMantissa {
+				s.error("illegal hexadecimal number")
+			}
+		} else {
+			// octal int or float
+			has8or9 := false
+			for isDecimal(ch) {
+				if ch > '7' {
+					has8or9 = true
+				}
+				ch = s.next()
+			}
+			if s.Mode&ScanFloats != 0 && (ch == '.' || ch == 'e' || ch == 'E') {
+				// float
+				ch = s.scanFraction(ch)
+				ch = s.scanExponent(ch)
+				return Float, ch
+			}
+			// octal int
+			if has8or9 {
+				s.error("illegal octal number")
+			}
+		}
+		return Int, ch
+	}
+	// decimal int or float
+	ch = s.scanMantissa(ch)
+	if s.Mode&ScanFloats != 0 && (ch == '.' || ch == 'e' || ch == 'E') {
+		// float
+		ch = s.scanFraction(ch)
+		ch = s.scanExponent(ch)
+		return Float, ch
+	}
+	return Int, ch
+}
+
+func (s *Scanner) scanDigits(ch rune, base, n int) rune {
+	for n > 0 && digitVal(ch) < base {
+		ch = s.next()
+		n--
+	}
+	if n > 0 {
+		s.error("illegal char escape")
+	}
+	return ch
+}
+
+func (s *Scanner) scanEscape(quote rune) rune {
+	ch := s.next() // read character after '/'
+	switch ch {
+	case 'a', 'b', 'f', 'n', 'r', 't', 'v', '\\', quote:
+		// nothing to do
+		ch = s.next()
+	case '0', '1', '2', '3', '4', '5', '6', '7':
+		ch = s.scanDigits(ch, 8, 3)
+	case 'x':
+		ch = s.scanDigits(s.next(), 16, 2)
+	case 'u':
+		ch = s.scanDigits(s.next(), 16, 4)
+	case 'U':
+		ch = s.scanDigits(s.next(), 16, 8)
+	default:
+		s.error("illegal char escape")
+	}
+	return ch
+}
+
+func (s *Scanner) scanString(quote rune) (n int) {
+	ch := s.next() // read character after quote
+	for ch != quote {
+		if ch == '\n' || ch < 0 {
+			s.error("literal not terminated")
+			return
+		}
+		if ch == '\\' {
+			ch = s.scanEscape(quote)
+		} else {
+			ch = s.next()
+		}
+		n++
+	}
+	return
+}
+
+func (s *Scanner) scanRawString() {
+	ch := s.next() // read character after '`'
+	for ch != '`' {
+		if ch < 0 {
+			s.error("literal not terminated")
+			return
+		}
+		ch = s.next()
+	}
+}
+
+func (s *Scanner) scanChar() {
+	if s.scanString('\'') != 1 {
+		s.error("illegal char literal")
+	}
+}
+
+func (s *Scanner) scanComment(ch rune) rune {
+	// ch == '/' || ch == '*'
+	if ch == '/' {
+		// line comment
+		ch = s.next() // read character after "//"
+		for ch != '\n' && ch >= 0 {
+			ch = s.next()
+		}
+		return ch
+	}
+
+	// general comment
+	ch = s.next() // read character after "/*"
+	for {
+		if ch < 0 {
+			s.error("comment not terminated")
+			break
+		}
+		ch0 := ch
+		ch = s.next()
+		if ch0 == '*' && ch == '/' {
+			ch = s.next()
+			break
+		}
+	}
+	return ch
+}
+
+// Scan reads the next token or Unicode character from source and returns it.
+// It only recognizes tokens t for which the respective Mode bit (1<<-t) is set.
+// It returns EOF at the end of the source. It reports scanner errors (read and
+// token errors) by calling s.Error, if not nil; otherwise it prints an error
+// message to os.Stderr.
+func (s *Scanner) Scan() rune {
+	ch := s.Peek()
+
+	// reset token text position
+	s.tokPos = -1
+	s.Line = 0
+
+redo:
+	// skip white space
+	for s.Whitespace&(1<<uint(ch)) != 0 {
+		ch = s.next()
+	}
+
+	// start collecting token text
+	s.tokBuf.Reset()
+	s.tokPos = s.srcPos - s.lastCharLen
+
+	// set token position
+	// (this is a slightly optimized version of the code in Pos())
+	s.Offset = s.srcBufOffset + s.tokPos
+	if s.column > 0 {
+		// common case: last character was not a '\n'
+		s.Line = s.line
+		s.Column = s.column
+	} else {
+		// last character was a '\n'
+		// (we cannot be at the beginning of the source
+		// since we have called next() at least once)
+		s.Line = s.line - 1
+		s.Column = s.lastLineLen
+	}
+
+	// determine token value
+	tok := ch
+	switch {
+	case s.isIdentRune(ch, 0):
+		if s.Mode&ScanIdents != 0 {
+			tok = Ident
+			ch = s.scanIdentifier()
+		} else {
+			ch = s.next()
+		}
+	case isDecimal(ch):
+		if s.Mode&(ScanInts|ScanFloats) != 0 {
+			tok, ch = s.scanNumber(ch)
+		} else {
+			ch = s.next()
+		}
+	default:
+		switch ch {
+		case '"':
+			if s.Mode&ScanStrings != 0 {
+				s.scanString('"')
+				tok = String
+			}
+			ch = s.next()
+		case '\'':
+			if s.Mode&ScanChars != 0 {
+				s.scanChar()
+				tok = Char
+			}
+			ch = s.next()
+		case '.':
+			ch = s.next()
+			if isDecimal(ch) && s.Mode&ScanFloats != 0 {
+				tok = Float
+				ch = s.scanMantissa(ch)
+				ch = s.scanExponent(ch)
+			}
+		case '/':
+			ch = s.next()
+			if (ch == '/' || ch == '*') && s.Mode&ScanComments != 0 {
+				if s.Mode&SkipComments != 0 {
+					s.tokPos = -1 // don't collect token text
+					ch = s.scanComment(ch)
+					goto redo
+				}
+				ch = s.scanComment(ch)
+				tok = Comment
+			}
+		case '`':
+			if s.Mode&ScanRawStrings != 0 {
+				s.scanRawString()
+				tok = String
+			}
+			ch = s.next()
+		default:
+			ch = s.next()
+		}
+	}
+
+	// end of token text
+	s.tokEnd = s.srcPos - s.lastCharLen
+
+	s.ch = ch
+	return tok
+}
+
+// Pos returns the position of the character immediately after
+// the character or token returned by the last call to Next or Scan.
+func (s *Scanner) Pos() (pos Position) {
+	pos.Filename = s.Filename
+	pos.Offset = s.srcBufOffset + s.srcPos - s.lastCharLen
+	switch {
+	case s.column > 0:
+		// common case: last character was not a '\n'
+		pos.Line = s.line
+		pos.Column = s.column
+	case s.lastLineLen > 0:
+		// last character was a '\n'
+		pos.Line = s.line - 1
+		pos.Column = s.lastLineLen
+	default:
+		// at the beginning of the source
+		pos.Line = 1
+		pos.Column = 1
+	}
+	return
+}
+
+// TokenText returns the string corresponding to the most recently scanned token.
+// Valid after calling Scan().
+func (s *Scanner) TokenText() string {
+	if s.tokPos < 0 {
+		// no token text
+		return ""
+	}
+
+	if s.tokEnd < 0 {
+		// if EOF was reached, s.tokEnd is set to -1 (s.srcPos == 0)
+		s.tokEnd = s.tokPos
+	}
+
+	if s.tokBuf.Len() == 0 {
+		// common case: the entire token text is still in srcBuf
+		return string(s.srcBuf[s.tokPos:s.tokEnd])
+	}
+
+	// part of the token text was saved in tokBuf: save the rest in
+	// tokBuf as well and return its content
+	s.tokBuf.Write(s.srcBuf[s.tokPos:s.tokEnd])
+	s.tokPos = s.tokEnd // ensure idempotency of TokenText() call
+	return s.tokBuf.String()
+}
diff --git a/src/text/scanner/scanner_test.go b/src/text/scanner/scanner_test.go
new file mode 100644
index 000000000..702fac2b1
--- /dev/null
+++ b/src/text/scanner/scanner_test.go
@@ -0,0 +1,618 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package scanner
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"testing"
+	"unicode/utf8"
+)
+
+// A StringReader delivers its data one string segment at a time via Read.
+type StringReader struct {
+	data []string
+	step int
+}
+
+func (r *StringReader) Read(p []byte) (n int, err error) {
+	if r.step < len(r.data) {
+		s := r.data[r.step]
+		n = copy(p, s)
+		r.step++
+	} else {
+		err = io.EOF
+	}
+	return
+}
+
+func readRuneSegments(t *testing.T, segments []string) {
+	got := ""
+	want := strings.Join(segments, "")
+	s := new(Scanner).Init(&StringReader{data: segments})
+	for {
+		ch := s.Next()
+		if ch == EOF {
+			break
+		}
+		got += string(ch)
+	}
+	if got != want {
+		t.Errorf("segments=%v got=%s want=%s", segments, got, want)
+	}
+}
+
+var segmentList = [][]string{
+	{},
+	{""},
+	{"日", "本語"},
+	{"\u65e5", "\u672c", "\u8a9e"},
+	{"\U000065e5", " ", "\U0000672c", "\U00008a9e"},
+	{"\xe6", "\x97\xa5\xe6", "\x9c\xac\xe8\xaa\x9e"},
+	{"Hello", ", ", "World", "!"},
+	{"Hello", ", ", "", "World", "!"},
+}
+
+func TestNext(t *testing.T) {
+	for _, s := range segmentList {
+		readRuneSegments(t, s)
+	}
+}
+
+type token struct {
+	tok  rune
+	text string
+}
+
+var f100 = "ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"
+
+var tokenList = []token{
+	{Comment, "// line comments"},
+	{Comment, "//"},
+	{Comment, "////"},
+	{Comment, "// comment"},
+	{Comment, "// /* comment */"},
+	{Comment, "// // comment //"},
+	{Comment, "//" + f100},
+
+	{Comment, "// general comments"},
+	{Comment, "/**/"},
+	{Comment, "/***/"},
+	{Comment, "/* comment */"},
+	{Comment, "/* // comment */"},
+	{Comment, "/* /* comment */"},
+	{Comment, "/*\n comment\n*/"},
+	{Comment, "/*" + f100 + "*/"},
+
+	{Comment, "// identifiers"},
+	{Ident, "a"},
+	{Ident, "a0"},
+	{Ident, "foobar"},
+	{Ident, "abc123"},
+	{Ident, "LGTM"},
+	{Ident, "_"},
+	{Ident, "_abc123"},
+	{Ident, "abc123_"},
+	{Ident, "_abc_123_"},
+	{Ident, "_äöü"},
+	{Ident, "_本"},
+	{Ident, "äöü"},
+	{Ident, "本"},
+	{Ident, "a۰۱۸"},
+	{Ident, "foo६४"},
+	{Ident, "bar９８７６"},
+	{Ident, f100},
+
+	{Comment, "// decimal ints"},
+	{Int, "0"},
+	{Int, "1"},
+	{Int, "9"},
+	{Int, "42"},
+	{Int, "1234567890"},
+
+	{Comment, "// octal ints"},
+	{Int, "00"},
+	{Int, "01"},
+	{Int, "07"},
+	{Int, "042"},
+	{Int, "01234567"},
+
+	{Comment, "// hexadecimal ints"},
+	{Int, "0x0"},
+	{Int, "0x1"},
+	{Int, "0xf"},
+	{Int, "0x42"},
+	{Int, "0x123456789abcDEF"},
+	{Int, "0x" + f100},
+	{Int, "0X0"},
+	{Int, "0X1"},
+	{Int, "0XF"},
+	{Int, "0X42"},
+	{Int, "0X123456789abcDEF"},
+	{Int, "0X" + f100},
+
+	{Comment, "// floats"},
+	{Float, "0."},
+	{Float, "1."},
+	{Float, "42."},
+	{Float, "01234567890."},
+	{Float, ".0"},
+	{Float, ".1"},
+	{Float, ".42"},
+	{Float, ".0123456789"},
+	{Float, "0.0"},
+	{Float, "1.0"},
+	{Float, "42.0"},
+	{Float, "01234567890.0"},
+	{Float, "0e0"},
+	{Float, "1e0"},
+	{Float, "42e0"},
+	{Float, "01234567890e0"},
+	{Float, "0E0"},
+	{Float, "1E0"},
+	{Float, "42E0"},
+	{Float, "01234567890E0"},
+	{Float, "0e+10"},
+	{Float, "1e-10"},
+	{Float, "42e+10"},
+	{Float, "01234567890e-10"},
+	{Float, "0E+10"},
+	{Float, "1E-10"},
+	{Float, "42E+10"},
+	{Float, "01234567890E-10"},
+
+	{Comment, "// chars"},
+	{Char, `' '`},
+	{Char, `'a'`},
+	{Char, `'本'`},
+	{Char, `'\a'`},
+	{Char, `'\b'`},
+	{Char, `'\f'`},
+	{Char, `'\n'`},
+	{Char, `'\r'`},
+	{Char, `'\t'`},
+	{Char, `'\v'`},
+	{Char, `'\''`},
+	{Char, `'\000'`},
+	{Char, `'\777'`},
+	{Char, `'\x00'`},
+	{Char, `'\xff'`},
+	{Char, `'\u0000'`},
+	{Char, `'\ufA16'`},
+	{Char, `'\U00000000'`},
+	{Char, `'\U0000ffAB'`},
+
+	{Comment, "// strings"},
+	{String, `" "`},
+	{String, `"a"`},
+	{String, `"本"`},
+	{String, `"\a"`},
+	{String, `"\b"`},
+	{String, `"\f"`},
+	{String, `"\n"`},
+	{String, `"\r"`},
+	{String, `"\t"`},
+	{String, `"\v"`},
+	{String, `"\""`},
+	{String, `"\000"`},
+	{String, `"\777"`},
+	{String, `"\x00"`},
+	{String, `"\xff"`},
+	{String, `"\u0000"`},
+	{String, `"\ufA16"`},
+	{String, `"\U00000000"`},
+	{String, `"\U0000ffAB"`},
+	{String, `"` + f100 + `"`},
+
+	{Comment, "// raw strings"},
+	{String, "``"},
+	{String, "`\\`"},
+	{String, "`" + "\n\n/* foobar */\n\n" + "`"},
+	{String, "`" + f100 + "`"},
+
+	{Comment, "// individual characters"},
+	// NUL character is not allowed
+	{'\x01', "\x01"},
+	{' ' - 1, string(' ' - 1)},
+	{'+', "+"},
+	{'/', "/"},
+	{'.', "."},
+	{'~', "~"},
+	{'(', "("},
+}
+
+func makeSource(pattern string) *bytes.Buffer {
+	var buf bytes.Buffer
+	for _, k := range tokenList {
+		fmt.Fprintf(&buf, pattern, k.text)
+	}
+	return &buf
+}
+
+func checkTok(t *testing.T, s *Scanner, line int, got, want rune, text string) {
+	if got != want {
+		t.Fatalf("tok = %s, want %s for %q", TokenString(got), TokenString(want), text)
+	}
+	if s.Line != line {
+		t.Errorf("line = %d, want %d for %q", s.Line, line, text)
+	}
+	stext := s.TokenText()
+	if stext != text {
+		t.Errorf("text = %q, want %q", stext, text)
+	} else {
+		// check idempotency of TokenText() call
+		stext = s.TokenText()
+		if stext != text {
+			t.Errorf("text = %q, want %q (idempotency check)", stext, text)
+		}
+	}
+}
+
+func countNewlines(s string) int {
+	n := 0
+	for _, ch := range s {
+		if ch == '\n' {
+			n++
+		}
+	}
+	return n
+}
+
+func testScan(t *testing.T, mode uint) {
+	s := new(Scanner).Init(makeSource(" \t%s\n"))
+	s.Mode = mode
+	tok := s.Scan()
+	line := 1
+	for _, k := range tokenList {
+		if mode&SkipComments == 0 || k.tok != Comment {
+			checkTok(t, s, line, tok, k.tok, k.text)
+			tok = s.Scan()
+		}
+		line += countNewlines(k.text) + 1 // each token is on a new line
+	}
+	checkTok(t, s, line, tok, EOF, "")
+}
+
+func TestScan(t *testing.T) {
+	testScan(t, GoTokens)
+	testScan(t, GoTokens&^SkipComments)
+}
+
+func TestPosition(t *testing.T) {
+	src := makeSource("\t\t\t\t%s\n")
+	s := new(Scanner).Init(src)
+	s.Mode = GoTokens &^ SkipComments
+	s.Scan()
+	pos := Position{"", 4, 1, 5}
+	for _, k := range tokenList {
+		if s.Offset != pos.Offset {
+			t.Errorf("offset = %d, want %d for %q", s.Offset, pos.Offset, k.text)
+		}
+		if s.Line != pos.Line {
+			t.Errorf("line = %d, want %d for %q", s.Line, pos.Line, k.text)
+		}
+		if s.Column != pos.Column {
+			t.Errorf("column = %d, want %d for %q", s.Column, pos.Column, k.text)
+		}
+		pos.Offset += 4 + len(k.text) + 1     // 4 tabs + token bytes + newline
+		pos.Line += countNewlines(k.text) + 1 // each token is on a new line
+		s.Scan()
+	}
+	// make sure there were no token-internal errors reported by scanner
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+}
+
+func TestScanZeroMode(t *testing.T) {
+	src := makeSource("%s\n")
+	str := src.String()
+	s := new(Scanner).Init(src)
+	s.Mode = 0       // don't recognize any token classes
+	s.Whitespace = 0 // don't skip any whitespace
+	tok := s.Scan()
+	for i, ch := range str {
+		if tok != ch {
+			t.Fatalf("%d. tok = %s, want %s", i, TokenString(tok), TokenString(ch))
+		}
+		tok = s.Scan()
+	}
+	if tok != EOF {
+		t.Fatalf("tok = %s, want EOF", TokenString(tok))
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+}
+
+func testScanSelectedMode(t *testing.T, mode uint, class rune) {
+	src := makeSource("%s\n")
+	s := new(Scanner).Init(src)
+	s.Mode = mode
+	tok := s.Scan()
+	for tok != EOF {
+		if tok < 0 && tok != class {
+			t.Fatalf("tok = %s, want %s", TokenString(tok), TokenString(class))
+		}
+		tok = s.Scan()
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+}
+
+func TestScanSelectedMask(t *testing.T) {
+	testScanSelectedMode(t, 0, 0)
+	testScanSelectedMode(t, ScanIdents, Ident)
+	// Don't test ScanInts and ScanNumbers since some parts of
+	// the floats in the source look like (illegal) octal ints
+	// and ScanNumbers may return either Int or Float.
+	testScanSelectedMode(t, ScanChars, Char)
+	testScanSelectedMode(t, ScanStrings, String)
+	testScanSelectedMode(t, SkipComments, 0)
+	testScanSelectedMode(t, ScanComments, Comment)
+}
+
+func TestScanCustomIdent(t *testing.T) {
+	const src = "faab12345 a12b123 a12 3b"
+	s := new(Scanner).Init(strings.NewReader(src))
+	// ident = ( 'a' | 'b' ) { digit } .
+	// digit = '0' .. '3' .
+	// with a maximum length of 4
+	s.IsIdentRune = func(ch rune, i int) bool {
+		return i == 0 && (ch == 'a' || ch == 'b') || 0 < i && i < 4 && '0' <= ch && ch <= '3'
+	}
+	checkTok(t, s, 1, s.Scan(), 'f', "f")
+	checkTok(t, s, 1, s.Scan(), Ident, "a")
+	checkTok(t, s, 1, s.Scan(), Ident, "a")
+	checkTok(t, s, 1, s.Scan(), Ident, "b123")
+	checkTok(t, s, 1, s.Scan(), Int, "45")
+	checkTok(t, s, 1, s.Scan(), Ident, "a12")
+	checkTok(t, s, 1, s.Scan(), Ident, "b123")
+	checkTok(t, s, 1, s.Scan(), Ident, "a12")
+	checkTok(t, s, 1, s.Scan(), Int, "3")
+	checkTok(t, s, 1, s.Scan(), Ident, "b")
+	checkTok(t, s, 1, s.Scan(), EOF, "")
+}
+
+func TestScanNext(t *testing.T) {
+	const BOM = '\uFEFF'
+	BOMs := string(BOM)
+	s := new(Scanner).Init(strings.NewReader(BOMs + "if a == bcd /* com" + BOMs + "ment */ {\n\ta += c\n}" + BOMs + "// line comment ending in eof"))
+	checkTok(t, s, 1, s.Scan(), Ident, "if") // the first BOM is ignored
+	checkTok(t, s, 1, s.Scan(), Ident, "a")
+	checkTok(t, s, 1, s.Scan(), '=', "=")
+	checkTok(t, s, 0, s.Next(), '=', "")
+	checkTok(t, s, 0, s.Next(), ' ', "")
+	checkTok(t, s, 0, s.Next(), 'b', "")
+	checkTok(t, s, 1, s.Scan(), Ident, "cd")
+	checkTok(t, s, 1, s.Scan(), '{', "{")
+	checkTok(t, s, 2, s.Scan(), Ident, "a")
+	checkTok(t, s, 2, s.Scan(), '+', "+")
+	checkTok(t, s, 0, s.Next(), '=', "")
+	checkTok(t, s, 2, s.Scan(), Ident, "c")
+	checkTok(t, s, 3, s.Scan(), '}', "}")
+	checkTok(t, s, 3, s.Scan(), BOM, BOMs)
+	checkTok(t, s, 3, s.Scan(), -1, "")
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+}
+
+func TestScanWhitespace(t *testing.T) {
+	var buf bytes.Buffer
+	var ws uint64
+	// start at 1, NUL character is not allowed
+	for ch := byte(1); ch < ' '; ch++ {
+		buf.WriteByte(ch)
+		ws |= 1 << ch
+	}
+	const orig = 'x'
+	buf.WriteByte(orig)
+
+	s := new(Scanner).Init(&buf)
+	s.Mode = 0
+	s.Whitespace = ws
+	tok := s.Scan()
+	if tok != orig {
+		t.Errorf("tok = %s, want %s", TokenString(tok), TokenString(orig))
+	}
+}
+
+func testError(t *testing.T, src, pos, msg string, tok rune) {
+	s := new(Scanner).Init(strings.NewReader(src))
+	errorCalled := false
+	s.Error = func(s *Scanner, m string) {
+		if !errorCalled {
+			// only look at first error
+			if p := s.Pos().String(); p != pos {
+				t.Errorf("pos = %q, want %q for %q", p, pos, src)
+			}
+			if m != msg {
+				t.Errorf("msg = %q, want %q for %q", m, msg, src)
+			}
+			errorCalled = true
+		}
+	}
+	tk := s.Scan()
+	if tk != tok {
+		t.Errorf("tok = %s, want %s for %q", TokenString(tk), TokenString(tok), src)
+	}
+	if !errorCalled {
+		t.Errorf("error handler not called for %q", src)
+	}
+	if s.ErrorCount == 0 {
+		t.Errorf("count = %d, want > 0 for %q", s.ErrorCount, src)
+	}
+}
+
+func TestError(t *testing.T) {
+	testError(t, "\x00", "1:1", "illegal character NUL", 0)
+	testError(t, "\x80", "1:1", "illegal UTF-8 encoding", utf8.RuneError)
+	testError(t, "\xff", "1:1", "illegal UTF-8 encoding", utf8.RuneError)
+
+	testError(t, "a\x00", "1:2", "illegal character NUL", Ident)
+	testError(t, "ab\x80", "1:3", "illegal UTF-8 encoding", Ident)
+	testError(t, "abc\xff", "1:4", "illegal UTF-8 encoding", Ident)
+
+	testError(t, `"a`+"\x00", "1:3", "illegal character NUL", String)
+	testError(t, `"ab`+"\x80", "1:4", "illegal UTF-8 encoding", String)
+	testError(t, `"abc`+"\xff", "1:5", "illegal UTF-8 encoding", String)
+
+	testError(t, "`a"+"\x00", "1:3", "illegal character NUL", String)
+	testError(t, "`ab"+"\x80", "1:4", "illegal UTF-8 encoding", String)
+	testError(t, "`abc"+"\xff", "1:5", "illegal UTF-8 encoding", String)
+
+	testError(t, `'\"'`, "1:3", "illegal char escape", Char)
+	testError(t, `"\'"`, "1:3", "illegal char escape", String)
+
+	testError(t, `01238`, "1:6", "illegal octal number", Int)
+	testError(t, `01238123`, "1:9", "illegal octal number", Int)
+	testError(t, `0x`, "1:3", "illegal hexadecimal number", Int)
+	testError(t, `0xg`, "1:3", "illegal hexadecimal number", Int)
+	testError(t, `'aa'`, "1:4", "illegal char literal", Char)
+
+	testError(t, `'`, "1:2", "literal not terminated", Char)
+	testError(t, `'`+"\n", "1:2", "literal not terminated", Char)
+	testError(t, `"abc`, "1:5", "literal not terminated", String)
+	testError(t, `"abc`+"\n", "1:5", "literal not terminated", String)
+	testError(t, "`abc\n", "2:1", "literal not terminated", String)
+	testError(t, `/*/`, "1:4", "comment not terminated", EOF)
+}
+
+// An errReader returns (0, err) where err is not io.EOF.
+type errReader struct{}
+
+func (errReader) Read(b []byte) (int, error) {
+	return 0, io.ErrNoProgress // some error that is not io.EOF
+}
+
+func TestIOError(t *testing.T) {
+	s := new(Scanner).Init(errReader{})
+	errorCalled := false
+	s.Error = func(s *Scanner, msg string) {
+		if !errorCalled {
+			if want := io.ErrNoProgress.Error(); msg != want {
+				t.Errorf("msg = %q, want %q", msg, want)
+			}
+			errorCalled = true
+		}
+	}
+	tok := s.Scan()
+	if tok != EOF {
+		t.Errorf("tok = %s, want EOF", TokenString(tok))
+	}
+	if !errorCalled {
+		t.Errorf("error handler not called")
+	}
+}
+
+func checkPos(t *testing.T, got, want Position) {
+	if got.Offset != want.Offset || got.Line != want.Line || got.Column != want.Column {
+		t.Errorf("got offset, line, column = %d, %d, %d; want %d, %d, %d",
+			got.Offset, got.Line, got.Column, want.Offset, want.Line, want.Column)
+	}
+}
+
+func checkNextPos(t *testing.T, s *Scanner, offset, line, column int, char rune) {
+	if ch := s.Next(); ch != char {
+		t.Errorf("ch = %s, want %s", TokenString(ch), TokenString(char))
+	}
+	want := Position{Offset: offset, Line: line, Column: column}
+	checkPos(t, s.Pos(), want)
+}
+
+func checkScanPos(t *testing.T, s *Scanner, offset, line, column int, char rune) {
+	want := Position{Offset: offset, Line: line, Column: column}
+	checkPos(t, s.Pos(), want)
+	if ch := s.Scan(); ch != char {
+		t.Errorf("ch = %s, want %s", TokenString(ch), TokenString(char))
+		if string(ch) != s.TokenText() {
+			t.Errorf("tok = %q, want %q", s.TokenText(), string(ch))
+		}
+	}
+	checkPos(t, s.Position, want)
+}
+
+func TestPos(t *testing.T) {
+	// corner case: empty source
+	s := new(Scanner).Init(strings.NewReader(""))
+	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
+	s.Peek() // peek doesn't affect the position
+	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
+
+	// corner case: source with only a newline
+	s = new(Scanner).Init(strings.NewReader("\n"))
+	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
+	checkNextPos(t, s, 1, 2, 1, '\n')
+	// after EOF position doesn't change
+	for i := 10; i > 0; i-- {
+		checkScanPos(t, s, 1, 2, 1, EOF)
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+
+	// corner case: source with only a single character
+	s = new(Scanner).Init(strings.NewReader("本"))
+	checkPos(t, s.Pos(), Position{Offset: 0, Line: 1, Column: 1})
+	checkNextPos(t, s, 3, 1, 2, '本')
+	// after EOF position doesn't change
+	for i := 10; i > 0; i-- {
+		checkScanPos(t, s, 3, 1, 2, EOF)
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+
+	// positions after calling Next
+	s = new(Scanner).Init(strings.NewReader("  foo६४  \n\n本語\n"))
+	checkNextPos(t, s, 1, 1, 2, ' ')
+	s.Peek() // peek doesn't affect the position
+	checkNextPos(t, s, 2, 1, 3, ' ')
+	checkNextPos(t, s, 3, 1, 4, 'f')
+	checkNextPos(t, s, 4, 1, 5, 'o')
+	checkNextPos(t, s, 5, 1, 6, 'o')
+	checkNextPos(t, s, 8, 1, 7, '६')
+	checkNextPos(t, s, 11, 1, 8, '४')
+	checkNextPos(t, s, 12, 1, 9, ' ')
+	checkNextPos(t, s, 13, 1, 10, ' ')
+	checkNextPos(t, s, 14, 2, 1, '\n')
+	checkNextPos(t, s, 15, 3, 1, '\n')
+	checkNextPos(t, s, 18, 3, 2, '本')
+	checkNextPos(t, s, 21, 3, 3, '語')
+	checkNextPos(t, s, 22, 4, 1, '\n')
+	// after EOF position doesn't change
+	for i := 10; i > 0; i-- {
+		checkScanPos(t, s, 22, 4, 1, EOF)
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+
+	// positions after calling Scan
+	s = new(Scanner).Init(strings.NewReader("abc\n本語\n\nx"))
+	s.Mode = 0
+	s.Whitespace = 0
+	checkScanPos(t, s, 0, 1, 1, 'a')
+	s.Peek() // peek doesn't affect the position
+	checkScanPos(t, s, 1, 1, 2, 'b')
+	checkScanPos(t, s, 2, 1, 3, 'c')
+	checkScanPos(t, s, 3, 1, 4, '\n')
+	checkScanPos(t, s, 4, 2, 1, '本')
+	checkScanPos(t, s, 7, 2, 2, '語')
+	checkScanPos(t, s, 10, 2, 3, '\n')
+	checkScanPos(t, s, 11, 3, 1, '\n')
+	checkScanPos(t, s, 12, 4, 1, 'x')
+	// after EOF position doesn't change
+	for i := 10; i > 0; i-- {
+		checkScanPos(t, s, 13, 4, 2, EOF)
+	}
+	if s.ErrorCount != 0 {
+		t.Errorf("%d errors", s.ErrorCount)
+	}
+}
diff --git a/src/text/tabwriter/example_test.go b/src/text/tabwriter/example_test.go
new file mode 100644
index 000000000..20443cb1f
--- /dev/null
+++ b/src/text/tabwriter/example_test.go
@@ -0,0 +1,38 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tabwriter_test
+
+import (
+	"fmt"
+	"os"
+	"text/tabwriter"
+)
+
+func ExampleWriter_Init() {
+	w := new(tabwriter.Writer)
+
+	// Format in tab-separated columns with a tab stop of 8.
+	w.Init(os.Stdout, 0, 8, 0, '\t', 0)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// Format right-aligned in space-separated columns of minimal width 5
+	// and at least one blank of padding (so wider column entries do not
+	// touch each other).
+	w.Init(os.Stdout, 5, 0, 1, ' ', tabwriter.AlignRight)
+	fmt.Fprintln(w, "a\tb\tc\td\t.")
+	fmt.Fprintln(w, "123\t12345\t1234567\t123456789\t.")
+	fmt.Fprintln(w)
+	w.Flush()
+
+	// output:
+	// a	b	c	d		.
+	// 123	12345	1234567	123456789	.
+	//
+	//     a     b       c         d.
+	//   123 12345 1234567 123456789.
+}
diff --git a/src/text/tabwriter/tabwriter.go b/src/text/tabwriter/tabwriter.go
new file mode 100644
index 000000000..c0c32d5de
--- /dev/null
+++ b/src/text/tabwriter/tabwriter.go
@@ -0,0 +1,558 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tabwriter implements a write filter (tabwriter.Writer) that
+// translates tabbed columns in input into properly aligned text.
+//
+// The package is using the Elastic Tabstops algorithm described at
+// http://nickgravgaard.com/elastictabstops/index.html.
+//
+package tabwriter
+
+import (
+	"bytes"
+	"io"
+	"unicode/utf8"
+)
+
+// ----------------------------------------------------------------------------
+// Filter implementation
+
+// A cell represents a segment of text terminated by tabs or line breaks.
+// The text itself is stored in a separate buffer; cell only describes the
+// segment's size in bytes, its width in runes, and whether it's an htab
+// ('\t') terminated cell.
+//
+type cell struct {
+	size  int  // cell size in bytes
+	width int  // cell width in runes
+	htab  bool // true if the cell is terminated by an htab ('\t')
+}
+
+// A Writer is a filter that inserts padding around tab-delimited
+// columns in its input to align them in the output.
+//
+// The Writer treats incoming bytes as UTF-8 encoded text consisting
+// of cells terminated by (horizontal or vertical) tabs or line
+// breaks (newline or formfeed characters). Cells in adjacent lines
+// constitute a column. The Writer inserts padding as needed to
+// make all cells in a column have the same width, effectively
+// aligning the columns. It assumes that all characters have the
+// same width except for tabs for which a tabwidth must be specified.
+// Note that cells are tab-terminated, not tab-separated: trailing
+// non-tab text at the end of a line does not form a column cell.
+//
+// The Writer assumes that all Unicode code points have the same width;
+// this may not be true in some fonts.
+//
+// If DiscardEmptyColumns is set, empty columns that are terminated
+// entirely by vertical (or "soft") tabs are discarded. Columns
+// terminated by horizontal (or "hard") tabs are not affected by
+// this flag.
+//
+// If a Writer is configured to filter HTML, HTML tags and entities
+// are passed through. The widths of tags and entities are
+// assumed to be zero (tags) and one (entities) for formatting purposes.
+//
+// A segment of text may be escaped by bracketing it with Escape
+// characters. The tabwriter passes escaped text segments through
+// unchanged. In particular, it does not interpret any tabs or line
+// breaks within the segment. If the StripEscape flag is set, the
+// Escape characters are stripped from the output; otherwise they
+// are passed through as well. For the purpose of formatting, the
+// width of the escaped text is always computed excluding the Escape
+// characters.
+//
+// The formfeed character ('\f') acts like a newline but it also
+// terminates all columns in the current line (effectively calling
+// Flush). Cells in the next line start new columns. Unless found
+// inside an HTML tag or inside an escaped text segment, formfeed
+// characters appear as newlines in the output.
+//
+// The Writer must buffer input internally, because proper spacing
+// of one line may depend on the cells in future lines. Clients must
+// call Flush when done calling Write.
+//
+type Writer struct {
+	// configuration
+	output   io.Writer
+	minwidth int
+	tabwidth int
+	padding  int
+	padbytes [8]byte
+	flags    uint
+
+	// current state
+	buf     bytes.Buffer // collected text excluding tabs or line breaks
+	pos     int          // buffer position up to which cell.width of incomplete cell has been computed
+	cell    cell         // current incomplete cell; cell.width is up to buf[pos] excluding ignored sections
+	endChar byte         // terminating char of escaped sequence (Escape for escapes, '>', ';' for HTML tags/entities, or 0)
+	lines   [][]cell     // list of lines; each line is a list of cells
+	widths  []int        // list of column widths in runes - re-used during formatting
+}
+
+func (b *Writer) addLine() { b.lines = append(b.lines, []cell{}) }
+
+// Reset the current state.
+func (b *Writer) reset() {
+	b.buf.Reset()
+	b.pos = 0
+	b.cell = cell{}
+	b.endChar = 0
+	b.lines = b.lines[0:0]
+	b.widths = b.widths[0:0]
+	b.addLine()
+}
+
+// Internal representation (current state):
+//
+// - all text written is appended to buf; tabs and line breaks are stripped away
+// - at any given time there is a (possibly empty) incomplete cell at the end
+//   (the cell starts after a tab or line break)
+// - cell.size is the number of bytes belonging to the cell so far
+// - cell.width is text width in runes of that cell from the start of the cell to
+//   position pos; html tags and entities are excluded from this width if html
+//   filtering is enabled
+// - the sizes and widths of processed text are kept in the lines list
+//   which contains a list of cells for each line
+// - the widths list is a temporary list with current widths used during
+//   formatting; it is kept in Writer because it's re-used
+//
+//                    |<---------- size ---------->|
+//                    |                            |
+//                    |<- width ->|<- ignored ->|  |
+//                    |           |             |  |
+// [---processed---tab------------<tag>...</tag>...]
+// ^                  ^                         ^
+// |                  |                         |
+// buf                start of incomplete cell  pos
+
+// Formatting can be controlled with these flags.
+const (
+	// Ignore html tags and treat entities (starting with '&'
+	// and ending in ';') as single characters (width = 1).
+	FilterHTML uint = 1 << iota
+
+	// Strip Escape characters bracketing escaped text segments
+	// instead of passing them through unchanged with the text.
+	StripEscape
+
+	// Force right-alignment of cell content.
+	// Default is left-alignment.
+	AlignRight
+
+	// Handle empty columns as if they were not present in
+	// the input in the first place.
+	DiscardEmptyColumns
+
+	// Always use tabs for indentation columns (i.e., padding of
+	// leading empty cells on the left) independent of padchar.
+	TabIndent
+
+	// Print a vertical bar ('|') between columns (after formatting).
+	// Discarded columns appear as zero-width columns ("||").
+	Debug
+)
+
+// A Writer must be initialized with a call to Init. The first parameter (output)
+// specifies the filter output. The remaining parameters control the formatting:
+//
+//	minwidth	minimal cell width including any padding
+//	tabwidth	width of tab characters (equivalent number of spaces)
+//	padding		padding added to a cell before computing its width
+//	padchar		ASCII char used for padding
+//			if padchar == '\t', the Writer will assume that the
+//			width of a '\t' in the formatted output is tabwidth,
+//			and cells are left-aligned independent of align_left
+//			(for correct-looking results, tabwidth must correspond
+//			to the tab width in the viewer displaying the result)
+//	flags		formatting control
+//
+func (b *Writer) Init(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
+	if minwidth < 0 || tabwidth < 0 || padding < 0 {
+		panic("negative minwidth, tabwidth, or padding")
+	}
+	b.output = output
+	b.minwidth = minwidth
+	b.tabwidth = tabwidth
+	b.padding = padding
+	for i := range b.padbytes {
+		b.padbytes[i] = padchar
+	}
+	if padchar == '\t' {
+		// tab padding enforces left-alignment
+		flags &^= AlignRight
+	}
+	b.flags = flags
+
+	b.reset()
+
+	return b
+}
+
+// debugging support (keep code around)
+func (b *Writer) dump() {
+	pos := 0
+	for i, line := range b.lines {
+		print("(", i, ") ")
+		for _, c := range line {
+			print("[", string(b.buf.Bytes()[pos:pos+c.size]), "]")
+			pos += c.size
+		}
+		print("\n")
+	}
+	print("\n")
+}
+
+// local error wrapper so we can distinguish errors we want to return
+// as errors from genuine panics (which we don't want to return as errors)
+type osError struct {
+	err error
+}
+
+func (b *Writer) write0(buf []byte) {
+	n, err := b.output.Write(buf)
+	if n != len(buf) && err == nil {
+		err = io.ErrShortWrite
+	}
+	if err != nil {
+		panic(osError{err})
+	}
+}
+
+func (b *Writer) writeN(src []byte, n int) {
+	for n > len(src) {
+		b.write0(src)
+		n -= len(src)
+	}
+	b.write0(src[0:n])
+}
+
+var (
+	newline = []byte{'\n'}
+	tabs    = []byte("\t\t\t\t\t\t\t\t")
+)
+
+func (b *Writer) writePadding(textw, cellw int, useTabs bool) {
+	if b.padbytes[0] == '\t' || useTabs {
+		// padding is done with tabs
+		if b.tabwidth == 0 {
+			return // tabs have no width - can't do any padding
+		}
+		// make cellw the smallest multiple of b.tabwidth
+		cellw = (cellw + b.tabwidth - 1) / b.tabwidth * b.tabwidth
+		n := cellw - textw // amount of padding
+		if n < 0 {
+			panic("internal error")
+		}
+		b.writeN(tabs, (n+b.tabwidth-1)/b.tabwidth)
+		return
+	}
+
+	// padding is done with non-tab characters
+	b.writeN(b.padbytes[0:], cellw-textw)
+}
+
+var vbar = []byte{'|'}
+
+func (b *Writer) writeLines(pos0 int, line0, line1 int) (pos int) {
+	pos = pos0
+	for i := line0; i < line1; i++ {
+		line := b.lines[i]
+
+		// if TabIndent is set, use tabs to pad leading empty cells
+		useTabs := b.flags&TabIndent != 0
+
+		for j, c := range line {
+			if j > 0 && b.flags&Debug != 0 {
+				// indicate column break
+				b.write0(vbar)
+			}
+
+			if c.size == 0 {
+				// empty cell
+				if j < len(b.widths) {
+					b.writePadding(c.width, b.widths[j], useTabs)
+				}
+			} else {
+				// non-empty cell
+				useTabs = false
+				if b.flags&AlignRight == 0 { // align left
+					b.write0(b.buf.Bytes()[pos : pos+c.size])
+					pos += c.size
+					if j < len(b.widths) {
+						b.writePadding(c.width, b.widths[j], false)
+					}
+				} else { // align right
+					if j < len(b.widths) {
+						b.writePadding(c.width, b.widths[j], false)
+					}
+					b.write0(b.buf.Bytes()[pos : pos+c.size])
+					pos += c.size
+				}
+			}
+		}
+
+		if i+1 == len(b.lines) {
+			// last buffered line - we don't have a newline, so just write
+			// any outstanding buffered data
+			b.write0(b.buf.Bytes()[pos : pos+b.cell.size])
+			pos += b.cell.size
+		} else {
+			// not the last line - write newline
+			b.write0(newline)
+		}
+	}
+	return
+}
+
+// Format the text between line0 and line1 (excluding line1); pos
+// is the buffer position corresponding to the beginning of line0.
+// Returns the buffer position corresponding to the beginning of
+// line1 and an error, if any.
+//
+func (b *Writer) format(pos0 int, line0, line1 int) (pos int) {
+	pos = pos0
+	column := len(b.widths)
+	for this := line0; this < line1; this++ {
+		line := b.lines[this]
+
+		if column < len(line)-1 {
+			// cell exists in this column => this line
+			// has more cells than the previous line
+			// (the last cell per line is ignored because cells are
+			// tab-terminated; the last cell per line describes the
+			// text before the newline/formfeed and does not belong
+			// to a column)
+
+			// print unprinted lines until beginning of block
+			pos = b.writeLines(pos, line0, this)
+			line0 = this
+
+			// column block begin
+			width := b.minwidth // minimal column width
+			discardable := true // true if all cells in this column are empty and "soft"
+			for ; this < line1; this++ {
+				line = b.lines[this]
+				if column < len(line)-1 {
+					// cell exists in this column
+					c := line[column]
+					// update width
+					if w := c.width + b.padding; w > width {
+						width = w
+					}
+					// update discardable
+					if c.width > 0 || c.htab {
+						discardable = false
+					}
+				} else {
+					break
+				}
+			}
+			// column block end
+
+			// discard empty columns if necessary
+			if discardable && b.flags&DiscardEmptyColumns != 0 {
+				width = 0
+			}
+
+			// format and print all columns to the right of this column
+			// (we know the widths of this column and all columns to the left)
+			b.widths = append(b.widths, width) // push width
+			pos = b.format(pos, line0, this)
+			b.widths = b.widths[0 : len(b.widths)-1] // pop width
+			line0 = this
+		}
+	}
+
+	// print unprinted lines until end
+	return b.writeLines(pos, line0, line1)
+}
+
+// Append text to current cell.
+func (b *Writer) append(text []byte) {
+	b.buf.Write(text)
+	b.cell.size += len(text)
+}
+
+// Update the cell width.
+func (b *Writer) updateWidth() {
+	b.cell.width += utf8.RuneCount(b.buf.Bytes()[b.pos:b.buf.Len()])
+	b.pos = b.buf.Len()
+}
+
+// To escape a text segment, bracket it with Escape characters.
+// For instance, the tab in this string "Ignore this tab: \xff\t\xff"
+// does not terminate a cell and constitutes a single character of
+// width one for formatting purposes.
+//
+// The value 0xff was chosen because it cannot appear in a valid UTF-8 sequence.
+//
+const Escape = '\xff'
+
+// Start escaped mode.
+func (b *Writer) startEscape(ch byte) {
+	switch ch {
+	case Escape:
+		b.endChar = Escape
+	case '<':
+		b.endChar = '>'
+	case '&':
+		b.endChar = ';'
+	}
+}
+
+// Terminate escaped mode. If the escaped text was an HTML tag, its width
+// is assumed to be zero for formatting purposes; if it was an HTML entity,
+// its width is assumed to be one. In all other cases, the width is the
+// unicode width of the text.
+//
+func (b *Writer) endEscape() {
+	switch b.endChar {
+	case Escape:
+		b.updateWidth()
+		if b.flags&StripEscape == 0 {
+			b.cell.width -= 2 // don't count the Escape chars
+		}
+	case '>': // tag of zero width
+	case ';':
+		b.cell.width++ // entity, count as one rune
+	}
+	b.pos = b.buf.Len()
+	b.endChar = 0
+}
+
+// Terminate the current cell by adding it to the list of cells of the
+// current line. Returns the number of cells in that line.
+//
+func (b *Writer) terminateCell(htab bool) int {
+	b.cell.htab = htab
+	line := &b.lines[len(b.lines)-1]
+	*line = append(*line, b.cell)
+	b.cell = cell{}
+	return len(*line)
+}
+
+func handlePanic(err *error, op string) {
+	if e := recover(); e != nil {
+		if nerr, ok := e.(osError); ok {
+			*err = nerr.err
+			return
+		}
+		panic("tabwriter: panic during " + op)
+	}
+}
+
+// Flush should be called after the last call to Write to ensure
+// that any data buffered in the Writer is written to output. Any
+// incomplete escape sequence at the end is considered
+// complete for formatting purposes.
+//
+func (b *Writer) Flush() (err error) {
+	defer b.reset() // even in the presence of errors
+	defer handlePanic(&err, "Flush")
+
+	// add current cell if not empty
+	if b.cell.size > 0 {
+		if b.endChar != 0 {
+			// inside escape - terminate it even if incomplete
+			b.endEscape()
+		}
+		b.terminateCell(false)
+	}
+
+	// format contents of buffer
+	b.format(0, 0, len(b.lines))
+
+	return
+}
+
+var hbar = []byte("---\n")
+
+// Write writes buf to the writer b.
+// The only errors returned are ones encountered
+// while writing to the underlying output stream.
+//
+func (b *Writer) Write(buf []byte) (n int, err error) {
+	defer handlePanic(&err, "Write")
+
+	// split text into cells
+	n = 0
+	for i, ch := range buf {
+		if b.endChar == 0 {
+			// outside escape
+			switch ch {
+			case '\t', '\v', '\n', '\f':
+				// end of cell
+				b.append(buf[n:i])
+				b.updateWidth()
+				n = i + 1 // ch consumed
+				ncells := b.terminateCell(ch == '\t')
+				if ch == '\n' || ch == '\f' {
+					// terminate line
+					b.addLine()
+					if ch == '\f' || ncells == 1 {
+						// A '\f' always forces a flush. Otherwise, if the previous
+						// line has only one cell which does not have an impact on
+						// the formatting of the following lines (the last cell per
+						// line is ignored by format()), thus we can flush the
+						// Writer contents.
+						if err = b.Flush(); err != nil {
+							return
+						}
+						if ch == '\f' && b.flags&Debug != 0 {
+							// indicate section break
+							b.write0(hbar)
+						}
+					}
+				}
+
+			case Escape:
+				// start of escaped sequence
+				b.append(buf[n:i])
+				b.updateWidth()
+				n = i
+				if b.flags&StripEscape != 0 {
+					n++ // strip Escape
+				}
+				b.startEscape(Escape)
+
+			case '<', '&':
+				// possibly an html tag/entity
+				if b.flags&FilterHTML != 0 {
+					// begin of tag/entity
+					b.append(buf[n:i])
+					b.updateWidth()
+					n = i
+					b.startEscape(ch)
+				}
+			}
+
+		} else {
+			// inside escape
+			if ch == b.endChar {
+				// end of tag/entity
+				j := i + 1
+				if ch == Escape && b.flags&StripEscape != 0 {
+					j = i // strip Escape
+				}
+				b.append(buf[n:j])
+				n = i + 1 // ch consumed
+				b.endEscape()
+			}
+		}
+	}
+
+	// append leftover text
+	b.append(buf[n:])
+	n = len(buf)
+	return
+}
+
+// NewWriter allocates and initializes a new tabwriter.Writer.
+// The parameters are the same as for the Init function.
+//
+func NewWriter(output io.Writer, minwidth, tabwidth, padding int, padchar byte, flags uint) *Writer {
+	return new(Writer).Init(output, minwidth, tabwidth, padding, padchar, flags)
+}
diff --git a/src/text/tabwriter/tabwriter_test.go b/src/text/tabwriter/tabwriter_test.go
new file mode 100644
index 000000000..9d3111e2c
--- /dev/null
+++ b/src/text/tabwriter/tabwriter_test.go
@@ -0,0 +1,652 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tabwriter_test
+
+import (
+	"io"
+	"testing"
+	. "text/tabwriter"
+)
+
+type buffer struct {
+	a []byte
+}
+
+func (b *buffer) init(n int) { b.a = make([]byte, 0, n) }
+
+func (b *buffer) clear() { b.a = b.a[0:0] }
+
+func (b *buffer) Write(buf []byte) (written int, err error) {
+	n := len(b.a)
+	m := len(buf)
+	if n+m <= cap(b.a) {
+		b.a = b.a[0 : n+m]
+		for i := 0; i < m; i++ {
+			b.a[n+i] = buf[i]
+		}
+	} else {
+		panic("buffer.Write: buffer too small")
+	}
+	return len(buf), nil
+}
+
+func (b *buffer) String() string { return string(b.a) }
+
+func write(t *testing.T, testname string, w *Writer, src string) {
+	written, err := io.WriteString(w, src)
+	if err != nil {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- write error: %v\n", testname, src, err)
+	}
+	if written != len(src) {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- written = %d, len(src) = %d\n", testname, src, written, len(src))
+	}
+}
+
+func verify(t *testing.T, testname string, w *Writer, b *buffer, src, expected string) {
+	err := w.Flush()
+	if err != nil {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- flush error: %v\n", testname, src, err)
+	}
+
+	res := b.String()
+	if res != expected {
+		t.Errorf("--- test: %s\n--- src:\n%q\n--- found:\n%q\n--- expected:\n%q\n", testname, src, res, expected)
+	}
+}
+
+func check(t *testing.T, testname string, minwidth, tabwidth, padding int, padchar byte, flags uint, src, expected string) {
+	var b buffer
+	b.init(1000)
+
+	var w Writer
+	w.Init(&b, minwidth, tabwidth, padding, padchar, flags)
+
+	// write all at once
+	title := testname + " (written all at once)"
+	b.clear()
+	write(t, title, &w, src)
+	verify(t, title, &w, &b, src, expected)
+
+	// write byte-by-byte
+	title = testname + " (written byte-by-byte)"
+	b.clear()
+	for i := 0; i < len(src); i++ {
+		write(t, title, &w, src[i:i+1])
+	}
+	verify(t, title, &w, &b, src, expected)
+
+	// write using Fibonacci slice sizes
+	title = testname + " (written in fibonacci slices)"
+	b.clear()
+	for i, d := 0, 0; i < len(src); {
+		write(t, title, &w, src[i:i+d])
+		i, d = i+d, d+1
+		if i+d > len(src) {
+			d = len(src) - i
+		}
+	}
+	verify(t, title, &w, &b, src, expected)
+}
+
+var tests = []struct {
+	testname                    string
+	minwidth, tabwidth, padding int
+	padchar                     byte
+	flags                       uint
+	src, expected               string
+}{
+	{
+		"1a",
+		8, 0, 1, '.', 0,
+		"",
+		"",
+	},
+
+	{
+		"1a debug",
+		8, 0, 1, '.', Debug,
+		"",
+		"",
+	},
+
+	{
+		"1b esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\xff",
+		"",
+	},
+
+	{
+		"1b esc",
+		8, 0, 1, '.', 0,
+		"\xff\xff",
+		"\xff\xff",
+	},
+
+	{
+		"1c esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\t\xff",
+		"\t",
+	},
+
+	{
+		"1c esc",
+		8, 0, 1, '.', 0,
+		"\xff\t\xff",
+		"\xff\t\xff",
+	},
+
+	{
+		"1d esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"\xff\"foo\t\n\tbar\"\xff",
+		"\"foo\t\n\tbar\"",
+	},
+
+	{
+		"1d esc",
+		8, 0, 1, '.', 0,
+		"\xff\"foo\t\n\tbar\"\xff",
+		"\xff\"foo\t\n\tbar\"\xff",
+	},
+
+	{
+		"1e esc stripped",
+		8, 0, 1, '.', StripEscape,
+		"abc\xff\tdef", // unterminated escape
+		"abc\tdef",
+	},
+
+	{
+		"1e esc",
+		8, 0, 1, '.', 0,
+		"abc\xff\tdef", // unterminated escape
+		"abc\xff\tdef",
+	},
+
+	{
+		"2",
+		8, 0, 1, '.', 0,
+		"\n\n\n",
+		"\n\n\n",
+	},
+
+	{
+		"3",
+		8, 0, 1, '.', 0,
+		"a\nb\nc",
+		"a\nb\nc",
+	},
+
+	{
+		"4a",
+		8, 0, 1, '.', 0,
+		"\t", // '\t' terminates an empty cell on last line - nothing to print
+		"",
+	},
+
+	{
+		"4b",
+		8, 0, 1, '.', AlignRight,
+		"\t", // '\t' terminates an empty cell on last line - nothing to print
+		"",
+	},
+
+	{
+		"5",
+		8, 0, 1, '.', 0,
+		"*\t*",
+		"*.......*",
+	},
+
+	{
+		"5b",
+		8, 0, 1, '.', 0,
+		"*\t*\n",
+		"*.......*\n",
+	},
+
+	{
+		"5c",
+		8, 0, 1, '.', 0,
+		"*\t*\t",
+		"*.......*",
+	},
+
+	{
+		"5c debug",
+		8, 0, 1, '.', Debug,
+		"*\t*\t",
+		"*.......|*",
+	},
+
+	{
+		"5d",
+		8, 0, 1, '.', AlignRight,
+		"*\t*\t",
+		".......**",
+	},
+
+	{
+		"6",
+		8, 0, 1, '.', 0,
+		"\t\n",
+		"........\n",
+	},
+
+	{
+		"7a",
+		8, 0, 1, '.', 0,
+		"a) foo",
+		"a) foo",
+	},
+
+	{
+		"7b",
+		8, 0, 1, ' ', 0,
+		"b) foo\tbar",
+		"b) foo  bar",
+	},
+
+	{
+		"7c",
+		8, 0, 1, '.', 0,
+		"c) foo\tbar\t",
+		"c) foo..bar",
+	},
+
+	{
+		"7d",
+		8, 0, 1, '.', 0,
+		"d) foo\tbar\n",
+		"d) foo..bar\n",
+	},
+
+	{
+		"7e",
+		8, 0, 1, '.', 0,
+		"e) foo\tbar\t\n",
+		"e) foo..bar.....\n",
+	},
+
+	{
+		"7f",
+		8, 0, 1, '.', FilterHTML,
+		"f) f&lt;o\t<b>bar</b>\t\n",
+		"f) f&lt;o..<b>bar</b>.....\n",
+	},
+
+	{
+		"7g",
+		8, 0, 1, '.', FilterHTML,
+		"g) f&lt;o\t<b>bar</b>\t non-terminated entity &amp",
+		"g) f&lt;o..<b>bar</b>..... non-terminated entity &amp",
+	},
+
+	{
+		"7g debug",
+		8, 0, 1, '.', FilterHTML | Debug,
+		"g) f&lt;o\t<b>bar</b>\t non-terminated entity &amp",
+		"g) f&lt;o..|<b>bar</b>.....| non-terminated entity &amp",
+	},
+
+	{
+		"8",
+		8, 0, 1, '*', 0,
+		"Hello, world!\n",
+		"Hello, world!\n",
+	},
+
+	{
+		"9a",
+		1, 0, 0, '.', 0,
+		"1\t2\t3\t4\n" +
+			"11\t222\t3333\t44444\n",
+
+		"1.2..3...4\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9b",
+		1, 0, 0, '.', FilterHTML,
+		"1\t2<!---\f--->\t3\t4\n" + // \f inside HTML is ignored
+			"11\t222\t3333\t44444\n",
+
+		"1.2<!---\f--->..3...4\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9c",
+		1, 0, 0, '.', 0,
+		"1\t2\t3\t4\f" + // \f causes a newline and flush
+			"11\t222\t3333\t44444\n",
+
+		"1234\n" +
+			"11222333344444\n",
+	},
+
+	{
+		"9c debug",
+		1, 0, 0, '.', Debug,
+		"1\t2\t3\t4\f" + // \f causes a newline and flush
+			"11\t222\t3333\t44444\n",
+
+		"1|2|3|4\n" +
+			"---\n" +
+			"11|222|3333|44444\n",
+	},
+
+	{
+		"10a",
+		5, 0, 0, '.', 0,
+		"1\t2\t3\t4\n",
+		"1....2....3....4\n",
+	},
+
+	{
+		"10b",
+		5, 0, 0, '.', 0,
+		"1\t2\t3\t4\t\n",
+		"1....2....3....4....\n",
+	},
+
+	{
+		"11",
+		8, 0, 1, '.', 0,
+		"本\tb\tc\n" +
+			"aa\t\u672c\u672c\u672c\tcccc\tddddd\n" +
+			"aaa\tbbbb\n",
+
+		"本.......b.......c\n" +
+			"aa......本本本.....cccc....ddddd\n" +
+			"aaa.....bbbb\n",
+	},
+
+	{
+		"12a",
+		8, 0, 1, ' ', AlignRight,
+		"a\tè\tc\t\n" +
+			"aa\tèèè\tcccc\tddddd\t\n" +
+			"aaa\tèèèè\t\n",
+
+		"       a       è       c\n" +
+			"      aa     èèè    cccc   ddddd\n" +
+			"     aaa    èèèè\n",
+	},
+
+	{
+		"12b",
+		2, 0, 0, ' ', 0,
+		"a\tb\tc\n" +
+			"aa\tbbb\tcccc\n" +
+			"aaa\tbbbb\n",
+
+		"a  b  c\n" +
+			"aa bbbcccc\n" +
+			"aaabbbb\n",
+	},
+
+	{
+		"12c",
+		8, 0, 1, '_', 0,
+		"a\tb\tc\n" +
+			"aa\tbbb\tcccc\n" +
+			"aaa\tbbbb\n",
+
+		"a_______b_______c\n" +
+			"aa______bbb_____cccc\n" +
+			"aaa_____bbbb\n",
+	},
+
+	{
+		"13a",
+		4, 0, 1, '-', 0,
+		"4444\t日本語\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t999999999\t0000000000\n",
+
+		"4444------日本語-22--1---333\n" +
+			"999999999-22\n" +
+			"7---------22\n" +
+			"------------------88888888\n" +
+			"\n" +
+			"666666-666666-666666----4444\n" +
+			"1------1------999999999-0000000000\n",
+	},
+
+	{
+		"13b",
+		4, 0, 3, '.', 0,
+		"4444\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t999999999\t0000000000\n",
+
+		"4444........333...22...1...333\n" +
+			"999999999...22\n" +
+			"7...........22\n" +
+			"....................88888888\n" +
+			"\n" +
+			"666666...666666...666666......4444\n" +
+			"1........1........999999999...0000000000\n",
+	},
+
+	{
+		"13c",
+		8, 8, 1, '\t', FilterHTML,
+		"4444\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t22\n" +
+			"\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t4444\n" +
+			"1\t1\t<font color=red attr=日本語>999999999</font>\t0000000000\n",
+
+		"4444\t\t333\t22\t1\t333\n" +
+			"999999999\t22\n" +
+			"7\t\t22\n" +
+			"\t\t\t\t88888888\n" +
+			"\n" +
+			"666666\t666666\t666666\t\t4444\n" +
+			"1\t1\t<font color=red attr=日本語>999999999</font>\t0000000000\n",
+	},
+
+	{
+		"14",
+		1, 0, 2, ' ', AlignRight,
+		".0\t.3\t2.4\t-5.1\t\n" +
+			"23.0\t12345678.9\t2.4\t-989.4\t\n" +
+			"5.1\t12.0\t2.4\t-7.0\t\n" +
+			".0\t0.0\t332.0\t8908.0\t\n" +
+			".0\t-.3\t456.4\t22.1\t\n" +
+			".0\t1.2\t44.4\t-13.3\t\t",
+
+		"    .0          .3    2.4    -5.1\n" +
+			"  23.0  12345678.9    2.4  -989.4\n" +
+			"   5.1        12.0    2.4    -7.0\n" +
+			"    .0         0.0  332.0  8908.0\n" +
+			"    .0         -.3  456.4    22.1\n" +
+			"    .0         1.2   44.4   -13.3",
+	},
+
+	{
+		"14 debug",
+		1, 0, 2, ' ', AlignRight | Debug,
+		".0\t.3\t2.4\t-5.1\t\n" +
+			"23.0\t12345678.9\t2.4\t-989.4\t\n" +
+			"5.1\t12.0\t2.4\t-7.0\t\n" +
+			".0\t0.0\t332.0\t8908.0\t\n" +
+			".0\t-.3\t456.4\t22.1\t\n" +
+			".0\t1.2\t44.4\t-13.3\t\t",
+
+		"    .0|          .3|    2.4|    -5.1|\n" +
+			"  23.0|  12345678.9|    2.4|  -989.4|\n" +
+			"   5.1|        12.0|    2.4|    -7.0|\n" +
+			"    .0|         0.0|  332.0|  8908.0|\n" +
+			"    .0|         -.3|  456.4|    22.1|\n" +
+			"    .0|         1.2|   44.4|   -13.3|",
+	},
+
+	{
+		"15a",
+		4, 0, 0, '.', 0,
+		"a\t\tb",
+		"a.......b",
+	},
+
+	{
+		"15b",
+		4, 0, 0, '.', DiscardEmptyColumns,
+		"a\t\tb", // htabs - do not discard column
+		"a.......b",
+	},
+
+	{
+		"15c",
+		4, 0, 0, '.', DiscardEmptyColumns,
+		"a\v\vb",
+		"a...b",
+	},
+
+	{
+		"15d",
+		4, 0, 0, '.', AlignRight | DiscardEmptyColumns,
+		"a\v\vb",
+		"...ab",
+	},
+
+	{
+		"16a",
+		100, 100, 0, '\t', 0,
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16b",
+		100, 100, 0, '\t', DiscardEmptyColumns,
+		"a\vb\v\vd\n" +
+			"a\vb\v\vd\ve\n" +
+			"a\n" +
+			"a\vb\vc\vd\n" +
+			"a\vb\vc\vd\ve\n",
+
+		"a\tb\td\n" +
+			"a\tb\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16b debug",
+		100, 100, 0, '\t', DiscardEmptyColumns | Debug,
+		"a\vb\v\vd\n" +
+			"a\vb\v\vd\ve\n" +
+			"a\n" +
+			"a\vb\vc\vd\n" +
+			"a\vb\vc\vd\ve\n",
+
+		"a\t|b\t||d\n" +
+			"a\t|b\t||d\t|e\n" +
+			"a\n" +
+			"a\t|b\t|c\t|d\n" +
+			"a\t|b\t|c\t|d\t|e\n",
+	},
+
+	{
+		"16c",
+		100, 100, 0, '\t', DiscardEmptyColumns,
+		"a\tb\t\td\n" + // hard tabs - do not discard column
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\tb\t\td\n" +
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+	},
+
+	{
+		"16c debug",
+		100, 100, 0, '\t', DiscardEmptyColumns | Debug,
+		"a\tb\t\td\n" + // hard tabs - do not discard column
+			"a\tb\t\td\te\n" +
+			"a\n" +
+			"a\tb\tc\td\n" +
+			"a\tb\tc\td\te\n",
+
+		"a\t|b\t|\t|d\n" +
+			"a\t|b\t|\t|d\t|e\n" +
+			"a\n" +
+			"a\t|b\t|c\t|d\n" +
+			"a\t|b\t|c\t|d\t|e\n",
+	},
+}
+
+func Test(t *testing.T) {
+	for _, e := range tests {
+		check(t, e.testname, e.minwidth, e.tabwidth, e.padding, e.padchar, e.flags, e.src, e.expected)
+	}
+}
+
+type panicWriter struct{}
+
+func (panicWriter) Write([]byte) (int, error) {
+	panic("cannot write")
+}
+
+func wantPanicString(t *testing.T, want string) {
+	if e := recover(); e != nil {
+		got, ok := e.(string)
+		switch {
+		case !ok:
+			t.Errorf("got %v (%T), want panic string", e, e)
+		case got != want:
+			t.Errorf("wrong panic message: got %q, want %q", got, want)
+		}
+	}
+}
+
+func TestPanicDuringFlush(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Flush")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a")
+	w.Flush()
+	t.Errorf("failed to panic during Flush")
+}
+
+func TestPanicDuringWrite(t *testing.T) {
+	defer wantPanicString(t, "tabwriter: panic during Write")
+	var p panicWriter
+	w := new(Writer)
+	w.Init(p, 0, 0, 5, ' ', 0)
+	io.WriteString(w, "a\n\n") // the second \n triggers a call to w.Write and thus a panic
+	t.Errorf("failed to panic during Write")
+}
diff --git a/src/text/template/doc.go b/src/text/template/doc.go
new file mode 100644
index 000000000..7c6efd59c
--- /dev/null
+++ b/src/text/template/doc.go
@@ -0,0 +1,405 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Package template implements data-driven templates for generating textual output.
+
+To generate HTML output, see package html/template, which has the same interface
+as this package but automatically secures HTML output against certain attacks.
+
+Templates are executed by applying them to a data structure. Annotations in the
+template refer to elements of the data structure (typically a field of a struct
+or a key in a map) to control execution and derive values to be displayed.
+Execution of the template walks the structure and sets the cursor, represented
+by a period '.' and called "dot", to the value at the current location in the
+structure as execution proceeds.
+
+The input text for a template is UTF-8-encoded text in any format.
+"Actions"--data evaluations or control structures--are delimited by
+"{{" and "}}"; all text outside actions is copied to the output unchanged.
+Actions may not span newlines, although comments can.
+
+Once parsed, a template may be executed safely in parallel.
+
+Here is a trivial example that prints "17 items are made of wool".
+
+	type Inventory struct {
+		Material string
+		Count    uint
+	}
+	sweaters := Inventory{"wool", 17}
+	tmpl, err := template.New("test").Parse("{{.Count}} items are made of {{.Material}}")
+	if err != nil { panic(err) }
+	err = tmpl.Execute(os.Stdout, sweaters)
+	if err != nil { panic(err) }
+
+More intricate examples appear below.
+
+Actions
+
+Here is the list of actions. "Arguments" and "pipelines" are evaluations of
+data, defined in detail below.
+
+*/
+//	{{/* a comment */}}
+//		A comment; discarded. May contain newlines.
+//		Comments do not nest and must start and end at the
+//		delimiters, as shown here.
+/*
+
+	{{pipeline}}
+		The default textual representation of the value of the pipeline
+		is copied to the output.
+
+	{{if pipeline}} T1 {{end}}
+		If the value of the pipeline is empty, no output is generated;
+		otherwise, T1 is executed.  The empty values are false, 0, any
+		nil pointer or interface value, and any array, slice, map, or
+		string of length zero.
+		Dot is unaffected.
+
+	{{if pipeline}} T1 {{else}} T0 {{end}}
+		If the value of the pipeline is empty, T0 is executed;
+		otherwise, T1 is executed.  Dot is unaffected.
+
+	{{if pipeline}} T1 {{else if pipeline}} T0 {{end}}
+		To simplify the appearance of if-else chains, the else action
+		of an if may include another if directly; the effect is exactly
+		the same as writing
+			{{if pipeline}} T1 {{else}}{{if pipeline}} T0 {{end}}{{end}}
+
+	{{range pipeline}} T1 {{end}}
+		The value of the pipeline must be an array, slice, map, or channel.
+		If the value of the pipeline has length zero, nothing is output;
+		otherwise, dot is set to the successive elements of the array,
+		slice, or map and T1 is executed. If the value is a map and the
+		keys are of basic type with a defined order ("comparable"), the
+		elements will be visited in sorted key order.
+
+	{{range pipeline}} T1 {{else}} T0 {{end}}
+		The value of the pipeline must be an array, slice, map, or channel.
+		If the value of the pipeline has length zero, dot is unaffected and
+		T0 is executed; otherwise, dot is set to the successive elements
+		of the array, slice, or map and T1 is executed.
+
+	{{template "name"}}
+		The template with the specified name is executed with nil data.
+
+	{{template "name" pipeline}}
+		The template with the specified name is executed with dot set
+		to the value of the pipeline.
+
+	{{with pipeline}} T1 {{end}}
+		If the value of the pipeline is empty, no output is generated;
+		otherwise, dot is set to the value of the pipeline and T1 is
+		executed.
+
+	{{with pipeline}} T1 {{else}} T0 {{end}}
+		If the value of the pipeline is empty, dot is unaffected and T0
+		is executed; otherwise, dot is set to the value of the pipeline
+		and T1 is executed.
+
+Arguments
+
+An argument is a simple value, denoted by one of the following.
+
+	- A boolean, string, character, integer, floating-point, imaginary
+	  or complex constant in Go syntax. These behave like Go's untyped
+	  constants, although raw strings may not span newlines.
+	- The keyword nil, representing an untyped Go nil.
+	- The character '.' (period):
+		.
+	  The result is the value of dot.
+	- A variable name, which is a (possibly empty) alphanumeric string
+	  preceded by a dollar sign, such as
+		$piOver2
+	  or
+		$
+	  The result is the value of the variable.
+	  Variables are described below.
+	- The name of a field of the data, which must be a struct, preceded
+	  by a period, such as
+		.Field
+	  The result is the value of the field. Field invocations may be
+	  chained:
+	    .Field1.Field2
+	  Fields can also be evaluated on variables, including chaining:
+	    $x.Field1.Field2
+	- The name of a key of the data, which must be a map, preceded
+	  by a period, such as
+		.Key
+	  The result is the map element value indexed by the key.
+	  Key invocations may be chained and combined with fields to any
+	  depth:
+	    .Field1.Key1.Field2.Key2
+	  Although the key must be an alphanumeric identifier, unlike with
+	  field names they do not need to start with an upper case letter.
+	  Keys can also be evaluated on variables, including chaining:
+	    $x.key1.key2
+	- The name of a niladic method of the data, preceded by a period,
+	  such as
+		.Method
+	  The result is the value of invoking the method with dot as the
+	  receiver, dot.Method(). Such a method must have one return value (of
+	  any type) or two return values, the second of which is an error.
+	  If it has two and the returned error is non-nil, execution terminates
+	  and an error is returned to the caller as the value of Execute.
+	  Method invocations may be chained and combined with fields and keys
+	  to any depth:
+	    .Field1.Key1.Method1.Field2.Key2.Method2
+	  Methods can also be evaluated on variables, including chaining:
+	    $x.Method1.Field
+	- The name of a niladic function, such as
+		fun
+	  The result is the value of invoking the function, fun(). The return
+	  types and values behave as in methods. Functions and function
+	  names are described below.
+	- A parenthesized instance of one the above, for grouping. The result
+	  may be accessed by a field or map key invocation.
+		print (.F1 arg1) (.F2 arg2)
+		(.StructValuedMethod "arg").Field
+
+Arguments may evaluate to any type; if they are pointers the implementation
+automatically indirects to the base type when required.
+If an evaluation yields a function value, such as a function-valued
+field of a struct, the function is not invoked automatically, but it
+can be used as a truth value for an if action and the like. To invoke
+it, use the call function, defined below.
+
+A pipeline is a possibly chained sequence of "commands". A command is a simple
+value (argument) or a function or method call, possibly with multiple arguments:
+
+	Argument
+		The result is the value of evaluating the argument.
+	.Method [Argument...]
+		The method can be alone or the last element of a chain but,
+		unlike methods in the middle of a chain, it can take arguments.
+		The result is the value of calling the method with the
+		arguments:
+			dot.Method(Argument1, etc.)
+	functionName [Argument...]
+		The result is the value of calling the function associated
+		with the name:
+			function(Argument1, etc.)
+		Functions and function names are described below.
+
+Pipelines
+
+A pipeline may be "chained" by separating a sequence of commands with pipeline
+characters '|'. In a chained pipeline, the result of the each command is
+passed as the last argument of the following command. The output of the final
+command in the pipeline is the value of the pipeline.
+
+The output of a command will be either one value or two values, the second of
+which has type error. If that second value is present and evaluates to
+non-nil, execution terminates and the error is returned to the caller of
+Execute.
+
+Variables
+
+A pipeline inside an action may initialize a variable to capture the result.
+The initialization has syntax
+
+	$variable := pipeline
+
+where $variable is the name of the variable. An action that declares a
+variable produces no output.
+
+If a "range" action initializes a variable, the variable is set to the
+successive elements of the iteration.  Also, a "range" may declare two
+variables, separated by a comma:
+
+	range $index, $element := pipeline
+
+in which case $index and $element are set to the successive values of the
+array/slice index or map key and element, respectively.  Note that if there is
+only one variable, it is assigned the element; this is opposite to the
+convention in Go range clauses.
+
+A variable's scope extends to the "end" action of the control structure ("if",
+"with", or "range") in which it is declared, or to the end of the template if
+there is no such control structure.  A template invocation does not inherit
+variables from the point of its invocation.
+
+When execution begins, $ is set to the data argument passed to Execute, that is,
+to the starting value of dot.
+
+Examples
+
+Here are some example one-line templates demonstrating pipelines and variables.
+All produce the quoted word "output":
+
+	{{"\"output\""}}
+		A string constant.
+	{{`"output"`}}
+		A raw string constant.
+	{{printf "%q" "output"}}
+		A function call.
+	{{"output" | printf "%q"}}
+		A function call whose final argument comes from the previous
+		command.
+	{{printf "%q" (print "out" "put")}}
+		A parenthesized argument.
+	{{"put" | printf "%s%s" "out" | printf "%q"}}
+		A more elaborate call.
+	{{"output" | printf "%s" | printf "%q"}}
+		A longer chain.
+	{{with "output"}}{{printf "%q" .}}{{end}}
+		A with action using dot.
+	{{with $x := "output" | printf "%q"}}{{$x}}{{end}}
+		A with action that creates and uses a variable.
+	{{with $x := "output"}}{{printf "%q" $x}}{{end}}
+		A with action that uses the variable in another action.
+	{{with $x := "output"}}{{$x | printf "%q"}}{{end}}
+		The same, but pipelined.
+
+Functions
+
+During execution functions are found in two function maps: first in the
+template, then in the global function map. By default, no functions are defined
+in the template but the Funcs method can be used to add them.
+
+Predefined global functions are named as follows.
+
+	and
+		Returns the boolean AND of its arguments by returning the
+		first empty argument or the last argument, that is,
+		"and x y" behaves as "if x then y else x". All the
+		arguments are evaluated.
+	call
+		Returns the result of calling the first argument, which
+		must be a function, with the remaining arguments as parameters.
+		Thus "call .X.Y 1 2" is, in Go notation, dot.X.Y(1, 2) where
+		Y is a func-valued field, map entry, or the like.
+		The first argument must be the result of an evaluation
+		that yields a value of function type (as distinct from
+		a predefined function such as print). The function must
+		return either one or two result values, the second of which
+		is of type error. If the arguments don't match the function
+		or the returned error value is non-nil, execution stops.
+	html
+		Returns the escaped HTML equivalent of the textual
+		representation of its arguments.
+	index
+		Returns the result of indexing its first argument by the
+		following arguments. Thus "index x 1 2 3" is, in Go syntax,
+		x[1][2][3]. Each indexed item must be a map, slice, or array.
+	js
+		Returns the escaped JavaScript equivalent of the textual
+		representation of its arguments.
+	len
+		Returns the integer length of its argument.
+	not
+		Returns the boolean negation of its single argument.
+	or
+		Returns the boolean OR of its arguments by returning the
+		first non-empty argument or the last argument, that is,
+		"or x y" behaves as "if x then x else y". All the
+		arguments are evaluated.
+	print
+		An alias for fmt.Sprint
+	printf
+		An alias for fmt.Sprintf
+	println
+		An alias for fmt.Sprintln
+	urlquery
+		Returns the escaped value of the textual representation of
+		its arguments in a form suitable for embedding in a URL query.
+
+The boolean functions take any zero value to be false and a non-zero
+value to be true.
+
+There is also a set of binary comparison operators defined as
+functions:
+
+	eq
+		Returns the boolean truth of arg1 == arg2
+	ne
+		Returns the boolean truth of arg1 != arg2
+	lt
+		Returns the boolean truth of arg1 < arg2
+	le
+		Returns the boolean truth of arg1 <= arg2
+	gt
+		Returns the boolean truth of arg1 > arg2
+	ge
+		Returns the boolean truth of arg1 >= arg2
+
+For simpler multi-way equality tests, eq (only) accepts two or more
+arguments and compares the second and subsequent to the first,
+returning in effect
+
+	arg1==arg2 || arg1==arg3 || arg1==arg4 ...
+
+(Unlike with || in Go, however, eq is a function call and all the
+arguments will be evaluated.)
+
+The comparison functions work on basic types only (or named basic
+types, such as "type Celsius float32"). They implement the Go rules
+for comparison of values, except that size and exact type are
+ignored, so any integer value may be compared with any other integer
+value, any unsigned integer value may be compared with any other
+unsigned integer value, and so on. However, as usual, one may not
+compare an int with a float32 and so on.
+
+Associated templates
+
+Each template is named by a string specified when it is created. Also, each
+template is associated with zero or more other templates that it may invoke by
+name; such associations are transitive and form a name space of templates.
+
+A template may use a template invocation to instantiate another associated
+template; see the explanation of the "template" action above. The name must be
+that of a template associated with the template that contains the invocation.
+
+Nested template definitions
+
+When parsing a template, another template may be defined and associated with the
+template being parsed. Template definitions must appear at the top level of the
+template, much like global variables in a Go program.
+
+The syntax of such definitions is to surround each template declaration with a
+"define" and "end" action.
+
+The define action names the template being created by providing a string
+constant. Here is a simple example:
+
+	`{{define "T1"}}ONE{{end}}
+	{{define "T2"}}TWO{{end}}
+	{{define "T3"}}{{template "T1"}} {{template "T2"}}{{end}}
+	{{template "T3"}}`
+
+This defines two templates, T1 and T2, and a third T3 that invokes the other two
+when it is executed. Finally it invokes T3. If executed this template will
+produce the text
+
+	ONE TWO
+
+By construction, a template may reside in only one association. If it's
+necessary to have a template addressable from multiple associations, the
+template definition must be parsed multiple times to create distinct *Template
+values, or must be copied with the Clone or AddParseTree method.
+
+Parse may be called multiple times to assemble the various associated templates;
+see the ParseFiles and ParseGlob functions and methods for simple ways to parse
+related templates stored in files.
+
+A template may be executed directly or through ExecuteTemplate, which executes
+an associated template identified by name. To invoke our example above, we
+might write,
+
+	err := tmpl.Execute(os.Stdout, "no data needed")
+	if err != nil {
+		log.Fatalf("execution failed: %s", err)
+	}
+
+or to invoke a particular template explicitly by name,
+
+	err := tmpl.ExecuteTemplate(os.Stdout, "T2", "no data needed")
+	if err != nil {
+		log.Fatalf("execution failed: %s", err)
+	}
+
+*/
+package template
diff --git a/src/text/template/example_test.go b/src/text/template/example_test.go
new file mode 100644
index 000000000..de1d51851
--- /dev/null
+++ b/src/text/template/example_test.go
@@ -0,0 +1,71 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template_test
+
+import (
+	"log"
+	"os"
+	"text/template"
+)
+
+func ExampleTemplate() {
+	// Define a template.
+	const letter = `
+Dear {{.Name}},
+{{if .Attended}}
+It was a pleasure to see you at the wedding.{{else}}
+It is a shame you couldn't make it to the wedding.{{end}}
+{{with .Gift}}Thank you for the lovely {{.}}.
+{{end}}
+Best wishes,
+Josie
+`
+
+	// Prepare some data to insert into the template.
+	type Recipient struct {
+		Name, Gift string
+		Attended   bool
+	}
+	var recipients = []Recipient{
+		{"Aunt Mildred", "bone china tea set", true},
+		{"Uncle John", "moleskin pants", false},
+		{"Cousin Rodney", "", false},
+	}
+
+	// Create a new template and parse the letter into it.
+	t := template.Must(template.New("letter").Parse(letter))
+
+	// Execute the template for each recipient.
+	for _, r := range recipients {
+		err := t.Execute(os.Stdout, r)
+		if err != nil {
+			log.Println("executing template:", err)
+		}
+	}
+
+	// Output:
+	// Dear Aunt Mildred,
+	//
+	// It was a pleasure to see you at the wedding.
+	// Thank you for the lovely bone china tea set.
+	//
+	// Best wishes,
+	// Josie
+	//
+	// Dear Uncle John,
+	//
+	// It is a shame you couldn't make it to the wedding.
+	// Thank you for the lovely moleskin pants.
+	//
+	// Best wishes,
+	// Josie
+	//
+	// Dear Cousin Rodney,
+	//
+	// It is a shame you couldn't make it to the wedding.
+	//
+	// Best wishes,
+	// Josie
+}
diff --git a/src/text/template/examplefiles_test.go b/src/text/template/examplefiles_test.go
new file mode 100644
index 000000000..a15c7a62a
--- /dev/null
+++ b/src/text/template/examplefiles_test.go
@@ -0,0 +1,182 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template_test
+
+import (
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"text/template"
+)
+
+// templateFile defines the contents of a template to be stored in a file, for testing.
+type templateFile struct {
+	name     string
+	contents string
+}
+
+func createTestDir(files []templateFile) string {
+	dir, err := ioutil.TempDir("", "template")
+	if err != nil {
+		log.Fatal(err)
+	}
+	for _, file := range files {
+		f, err := os.Create(filepath.Join(dir, file.name))
+		if err != nil {
+			log.Fatal(err)
+		}
+		defer f.Close()
+		_, err = io.WriteString(f, file.contents)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+	return dir
+}
+
+// Here we demonstrate loading a set of templates from a directory.
+func ExampleTemplate_glob() {
+	// Here we create a temporary directory and populate it with our sample
+	// template definition files; usually the template files would already
+	// exist in some location known to the program.
+	dir := createTestDir([]templateFile{
+		// T0.tmpl is a plain template file that just invokes T1.
+		{"T0.tmpl", `T0 invokes T1: ({{template "T1"}})`},
+		// T1.tmpl defines a template, T1 that invokes T2.
+		{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+		// T2.tmpl defines a template T2.
+		{"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
+	})
+	// Clean up after the test; another quirk of running as an example.
+	defer os.RemoveAll(dir)
+
+	// pattern is the glob pattern used to find all the template files.
+	pattern := filepath.Join(dir, "*.tmpl")
+
+	// Here starts the example proper.
+	// T0.tmpl is the first name matched, so it becomes the starting template,
+	// the value returned by ParseGlob.
+	tmpl := template.Must(template.ParseGlob(pattern))
+
+	err := tmpl.Execute(os.Stdout, nil)
+	if err != nil {
+		log.Fatalf("template execution: %s", err)
+	}
+	// Output:
+	// T0 invokes T1: (T1 invokes T2: (This is T2))
+}
+
+// This example demonstrates one way to share some templates
+// and use them in different contexts. In this variant we add multiple driver
+// templates by hand to an existing bundle of templates.
+func ExampleTemplate_helpers() {
+	// Here we create a temporary directory and populate it with our sample
+	// template definition files; usually the template files would already
+	// exist in some location known to the program.
+	dir := createTestDir([]templateFile{
+		// T1.tmpl defines a template, T1 that invokes T2.
+		{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+		// T2.tmpl defines a template T2.
+		{"T2.tmpl", `{{define "T2"}}This is T2{{end}}`},
+	})
+	// Clean up after the test; another quirk of running as an example.
+	defer os.RemoveAll(dir)
+
+	// pattern is the glob pattern used to find all the template files.
+	pattern := filepath.Join(dir, "*.tmpl")
+
+	// Here starts the example proper.
+	// Load the helpers.
+	templates := template.Must(template.ParseGlob(pattern))
+	// Add one driver template to the bunch; we do this with an explicit template definition.
+	_, err := templates.Parse("{{define `driver1`}}Driver 1 calls T1: ({{template `T1`}})\n{{end}}")
+	if err != nil {
+		log.Fatal("parsing driver1: ", err)
+	}
+	// Add another driver template.
+	_, err = templates.Parse("{{define `driver2`}}Driver 2 calls T2: ({{template `T2`}})\n{{end}}")
+	if err != nil {
+		log.Fatal("parsing driver2: ", err)
+	}
+	// We load all the templates before execution. This package does not require
+	// that behavior but html/template's escaping does, so it's a good habit.
+	err = templates.ExecuteTemplate(os.Stdout, "driver1", nil)
+	if err != nil {
+		log.Fatalf("driver1 execution: %s", err)
+	}
+	err = templates.ExecuteTemplate(os.Stdout, "driver2", nil)
+	if err != nil {
+		log.Fatalf("driver2 execution: %s", err)
+	}
+	// Output:
+	// Driver 1 calls T1: (T1 invokes T2: (This is T2))
+	// Driver 2 calls T2: (This is T2)
+}
+
+// This example demonstrates how to use one group of driver
+// templates with distinct sets of helper templates.
+func ExampleTemplate_share() {
+	// Here we create a temporary directory and populate it with our sample
+	// template definition files; usually the template files would already
+	// exist in some location known to the program.
+	dir := createTestDir([]templateFile{
+		// T0.tmpl is a plain template file that just invokes T1.
+		{"T0.tmpl", "T0 ({{.}} version) invokes T1: ({{template `T1`}})\n"},
+		// T1.tmpl defines a template, T1 that invokes T2. Note T2 is not defined
+		{"T1.tmpl", `{{define "T1"}}T1 invokes T2: ({{template "T2"}}){{end}}`},
+	})
+	// Clean up after the test; another quirk of running as an example.
+	defer os.RemoveAll(dir)
+
+	// pattern is the glob pattern used to find all the template files.
+	pattern := filepath.Join(dir, "*.tmpl")
+
+	// Here starts the example proper.
+	// Load the drivers.
+	drivers := template.Must(template.ParseGlob(pattern))
+
+	// We must define an implementation of the T2 template. First we clone
+	// the drivers, then add a definition of T2 to the template name space.
+
+	// 1. Clone the helper set to create a new name space from which to run them.
+	first, err := drivers.Clone()
+	if err != nil {
+		log.Fatal("cloning helpers: ", err)
+	}
+	// 2. Define T2, version A, and parse it.
+	_, err = first.Parse("{{define `T2`}}T2, version A{{end}}")
+	if err != nil {
+		log.Fatal("parsing T2: ", err)
+	}
+
+	// Now repeat the whole thing, using a different version of T2.
+	// 1. Clone the drivers.
+	second, err := drivers.Clone()
+	if err != nil {
+		log.Fatal("cloning drivers: ", err)
+	}
+	// 2. Define T2, version B, and parse it.
+	_, err = second.Parse("{{define `T2`}}T2, version B{{end}}")
+	if err != nil {
+		log.Fatal("parsing T2: ", err)
+	}
+
+	// Execute the templates in the reverse order to verify the
+	// first is unaffected by the second.
+	err = second.ExecuteTemplate(os.Stdout, "T0.tmpl", "second")
+	if err != nil {
+		log.Fatalf("second execution: %s", err)
+	}
+	err = first.ExecuteTemplate(os.Stdout, "T0.tmpl", "first")
+	if err != nil {
+		log.Fatalf("first: execution: %s", err)
+	}
+
+	// Output:
+	// T0 (second version) invokes T1: (T1 invokes T2: (T2, version B))
+	// T0 (first version) invokes T1: (T1 invokes T2: (T2, version A))
+}
diff --git a/src/text/template/examplefunc_test.go b/src/text/template/examplefunc_test.go
new file mode 100644
index 000000000..080b5e3a0
--- /dev/null
+++ b/src/text/template/examplefunc_test.go
@@ -0,0 +1,54 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template_test
+
+import (
+	"log"
+	"os"
+	"strings"
+	"text/template"
+)
+
+// This example demonstrates a custom function to process template text.
+// It installs the strings.Title function and uses it to
+// Make Title Text Look Good In Our Template's Output.
+func ExampleTemplate_func() {
+	// First we create a FuncMap with which to register the function.
+	funcMap := template.FuncMap{
+		// The name "title" is what the function will be called in the template text.
+		"title": strings.Title,
+	}
+
+	// A simple template definition to test our function.
+	// We print the input text several ways:
+	// - the original
+	// - title-cased
+	// - title-cased and then printed with %q
+	// - printed with %q and then title-cased.
+	const templateText = `
+Input: {{printf "%q" .}}
+Output 0: {{title .}}
+Output 1: {{title . | printf "%q"}}
+Output 2: {{printf "%q" . | title}}
+`
+
+	// Create a template, add the function map, and parse the text.
+	tmpl, err := template.New("titleTest").Funcs(funcMap).Parse(templateText)
+	if err != nil {
+		log.Fatalf("parsing: %s", err)
+	}
+
+	// Run the template to verify the output.
+	err = tmpl.Execute(os.Stdout, "the go programming language")
+	if err != nil {
+		log.Fatalf("execution: %s", err)
+	}
+
+	// Output:
+	// Input: "the go programming language"
+	// Output 0: The Go Programming Language
+	// Output 1: "The Go Programming Language"
+	// Output 2: "The Go Programming Language"
+}
diff --git a/src/text/template/exec.go b/src/text/template/exec.go
new file mode 100644
index 000000000..8e155d478
--- /dev/null
+++ b/src/text/template/exec.go
@@ -0,0 +1,842 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"reflect"
+	"runtime"
+	"sort"
+	"strings"
+	"text/template/parse"
+)
+
+// state represents the state of an execution. It's not part of the
+// template so that multiple executions of the same template
+// can execute in parallel.
+type state struct {
+	tmpl *Template
+	wr   io.Writer
+	node parse.Node // current node, for errors
+	vars []variable // push-down stack of variable values.
+}
+
+// variable holds the dynamic value of a variable such as $, $x etc.
+type variable struct {
+	name  string
+	value reflect.Value
+}
+
+// push pushes a new variable on the stack.
+func (s *state) push(name string, value reflect.Value) {
+	s.vars = append(s.vars, variable{name, value})
+}
+
+// mark returns the length of the variable stack.
+func (s *state) mark() int {
+	return len(s.vars)
+}
+
+// pop pops the variable stack up to the mark.
+func (s *state) pop(mark int) {
+	s.vars = s.vars[0:mark]
+}
+
+// setVar overwrites the top-nth variable on the stack. Used by range iterations.
+func (s *state) setVar(n int, value reflect.Value) {
+	s.vars[len(s.vars)-n].value = value
+}
+
+// varValue returns the value of the named variable.
+func (s *state) varValue(name string) reflect.Value {
+	for i := s.mark() - 1; i >= 0; i-- {
+		if s.vars[i].name == name {
+			return s.vars[i].value
+		}
+	}
+	s.errorf("undefined variable: %s", name)
+	return zero
+}
+
+var zero reflect.Value
+
+// at marks the state to be on node n, for error reporting.
+func (s *state) at(node parse.Node) {
+	s.node = node
+}
+
+// doublePercent returns the string with %'s replaced by %%, if necessary,
+// so it can be used safely inside a Printf format string.
+func doublePercent(str string) string {
+	if strings.Contains(str, "%") {
+		str = strings.Replace(str, "%", "%%", -1)
+	}
+	return str
+}
+
+// errorf formats the error and terminates processing.
+func (s *state) errorf(format string, args ...interface{}) {
+	name := doublePercent(s.tmpl.Name())
+	if s.node == nil {
+		format = fmt.Sprintf("template: %s: %s", name, format)
+	} else {
+		location, context := s.tmpl.ErrorContext(s.node)
+		format = fmt.Sprintf("template: %s: executing %q at <%s>: %s", location, name, doublePercent(context), format)
+	}
+	panic(fmt.Errorf(format, args...))
+}
+
+// errRecover is the handler that turns panics into returns from the top
+// level of Parse.
+func errRecover(errp *error) {
+	e := recover()
+	if e != nil {
+		switch err := e.(type) {
+		case runtime.Error:
+			panic(e)
+		case error:
+			*errp = err
+		default:
+			panic(e)
+		}
+	}
+}
+
+// ExecuteTemplate applies the template associated with t that has the given name
+// to the specified data object and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel.
+func (t *Template) ExecuteTemplate(wr io.Writer, name string, data interface{}) error {
+	tmpl := t.tmpl[name]
+	if tmpl == nil {
+		return fmt.Errorf("template: no template %q associated with template %q", name, t.name)
+	}
+	return tmpl.Execute(wr, data)
+}
+
+// Execute applies a parsed template to the specified data object,
+// and writes the output to wr.
+// If an error occurs executing the template or writing its output,
+// execution stops, but partial results may already have been written to
+// the output writer.
+// A template may be executed safely in parallel.
+func (t *Template) Execute(wr io.Writer, data interface{}) (err error) {
+	defer errRecover(&err)
+	value := reflect.ValueOf(data)
+	state := &state{
+		tmpl: t,
+		wr:   wr,
+		vars: []variable{{"$", value}},
+	}
+	t.init()
+	if t.Tree == nil || t.Root == nil {
+		var b bytes.Buffer
+		for name, tmpl := range t.tmpl {
+			if tmpl.Tree == nil || tmpl.Root == nil {
+				continue
+			}
+			if b.Len() > 0 {
+				b.WriteString(", ")
+			}
+			fmt.Fprintf(&b, "%q", name)
+		}
+		var s string
+		if b.Len() > 0 {
+			s = "; defined templates are: " + b.String()
+		}
+		state.errorf("%q is an incomplete or empty template%s", t.Name(), s)
+	}
+	state.walk(value, t.Root)
+	return
+}
+
+// Walk functions step through the major pieces of the template structure,
+// generating output as they go.
+func (s *state) walk(dot reflect.Value, node parse.Node) {
+	s.at(node)
+	switch node := node.(type) {
+	case *parse.ActionNode:
+		// Do not pop variables so they persist until next end.
+		// Also, if the action declares variables, don't print the result.
+		val := s.evalPipeline(dot, node.Pipe)
+		if len(node.Pipe.Decl) == 0 {
+			s.printValue(node, val)
+		}
+	case *parse.IfNode:
+		s.walkIfOrWith(parse.NodeIf, dot, node.Pipe, node.List, node.ElseList)
+	case *parse.ListNode:
+		for _, node := range node.Nodes {
+			s.walk(dot, node)
+		}
+	case *parse.RangeNode:
+		s.walkRange(dot, node)
+	case *parse.TemplateNode:
+		s.walkTemplate(dot, node)
+	case *parse.TextNode:
+		if _, err := s.wr.Write(node.Text); err != nil {
+			s.errorf("%s", err)
+		}
+	case *parse.WithNode:
+		s.walkIfOrWith(parse.NodeWith, dot, node.Pipe, node.List, node.ElseList)
+	default:
+		s.errorf("unknown node: %s", node)
+	}
+}
+
+// walkIfOrWith walks an 'if' or 'with' node. The two control structures
+// are identical in behavior except that 'with' sets dot.
+func (s *state) walkIfOrWith(typ parse.NodeType, dot reflect.Value, pipe *parse.PipeNode, list, elseList *parse.ListNode) {
+	defer s.pop(s.mark())
+	val := s.evalPipeline(dot, pipe)
+	truth, ok := isTrue(val)
+	if !ok {
+		s.errorf("if/with can't use %v", val)
+	}
+	if truth {
+		if typ == parse.NodeWith {
+			s.walk(val, list)
+		} else {
+			s.walk(dot, list)
+		}
+	} else if elseList != nil {
+		s.walk(dot, elseList)
+	}
+}
+
+// isTrue reports whether the value is 'true', in the sense of not the zero of its type,
+// and whether the value has a meaningful truth value.
+func isTrue(val reflect.Value) (truth, ok bool) {
+	if !val.IsValid() {
+		// Something like var x interface{}, never set. It's a form of nil.
+		return false, true
+	}
+	switch val.Kind() {
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.String:
+		truth = val.Len() > 0
+	case reflect.Bool:
+		truth = val.Bool()
+	case reflect.Complex64, reflect.Complex128:
+		truth = val.Complex() != 0
+	case reflect.Chan, reflect.Func, reflect.Ptr, reflect.Interface:
+		truth = !val.IsNil()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		truth = val.Int() != 0
+	case reflect.Float32, reflect.Float64:
+		truth = val.Float() != 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		truth = val.Uint() != 0
+	case reflect.Struct:
+		truth = true // Struct values are always true.
+	default:
+		return
+	}
+	return truth, true
+}
+
+func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
+	s.at(r)
+	defer s.pop(s.mark())
+	val, _ := indirect(s.evalPipeline(dot, r.Pipe))
+	// mark top of stack before any variables in the body are pushed.
+	mark := s.mark()
+	oneIteration := func(index, elem reflect.Value) {
+		// Set top var (lexically the second if there are two) to the element.
+		if len(r.Pipe.Decl) > 0 {
+			s.setVar(1, elem)
+		}
+		// Set next var (lexically the first if there are two) to the index.
+		if len(r.Pipe.Decl) > 1 {
+			s.setVar(2, index)
+		}
+		s.walk(elem, r.List)
+		s.pop(mark)
+	}
+	switch val.Kind() {
+	case reflect.Array, reflect.Slice:
+		if val.Len() == 0 {
+			break
+		}
+		for i := 0; i < val.Len(); i++ {
+			oneIteration(reflect.ValueOf(i), val.Index(i))
+		}
+		return
+	case reflect.Map:
+		if val.Len() == 0 {
+			break
+		}
+		for _, key := range sortKeys(val.MapKeys()) {
+			oneIteration(key, val.MapIndex(key))
+		}
+		return
+	case reflect.Chan:
+		if val.IsNil() {
+			break
+		}
+		i := 0
+		for ; ; i++ {
+			elem, ok := val.Recv()
+			if !ok {
+				break
+			}
+			oneIteration(reflect.ValueOf(i), elem)
+		}
+		if i == 0 {
+			break
+		}
+		return
+	case reflect.Invalid:
+		break // An invalid value is likely a nil map, etc. and acts like an empty map.
+	default:
+		s.errorf("range can't iterate over %v", val)
+	}
+	if r.ElseList != nil {
+		s.walk(dot, r.ElseList)
+	}
+}
+
+func (s *state) walkTemplate(dot reflect.Value, t *parse.TemplateNode) {
+	s.at(t)
+	tmpl := s.tmpl.tmpl[t.Name]
+	if tmpl == nil {
+		s.errorf("template %q not defined", t.Name)
+	}
+	// Variables declared by the pipeline persist.
+	dot = s.evalPipeline(dot, t.Pipe)
+	newState := *s
+	newState.tmpl = tmpl
+	// No dynamic scoping: template invocations inherit no variables.
+	newState.vars = []variable{{"$", dot}}
+	newState.walk(dot, tmpl.Root)
+}
+
+// Eval functions evaluate pipelines, commands, and their elements and extract
+// values from the data structure by examining fields, calling methods, and so on.
+// The printing of those values happens only through walk functions.
+
+// evalPipeline returns the value acquired by evaluating a pipeline. If the
+// pipeline has a variable declaration, the variable will be pushed on the
+// stack. Callers should therefore pop the stack after they are finished
+// executing commands depending on the pipeline value.
+func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value reflect.Value) {
+	if pipe == nil {
+		return
+	}
+	s.at(pipe)
+	for _, cmd := range pipe.Cmds {
+		value = s.evalCommand(dot, cmd, value) // previous value is this one's final arg.
+		// If the object has type interface{}, dig down one level to the thing inside.
+		if value.Kind() == reflect.Interface && value.Type().NumMethod() == 0 {
+			value = reflect.ValueOf(value.Interface()) // lovely!
+		}
+	}
+	for _, variable := range pipe.Decl {
+		s.push(variable.Ident[0], value)
+	}
+	return value
+}
+
+func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
+	if len(args) > 1 || final.IsValid() {
+		s.errorf("can't give argument to non-function %s", args[0])
+	}
+}
+
+func (s *state) evalCommand(dot reflect.Value, cmd *parse.CommandNode, final reflect.Value) reflect.Value {
+	firstWord := cmd.Args[0]
+	switch n := firstWord.(type) {
+	case *parse.FieldNode:
+		return s.evalFieldNode(dot, n, cmd.Args, final)
+	case *parse.ChainNode:
+		return s.evalChainNode(dot, n, cmd.Args, final)
+	case *parse.IdentifierNode:
+		// Must be a function.
+		return s.evalFunction(dot, n, cmd, cmd.Args, final)
+	case *parse.PipeNode:
+		// Parenthesized pipeline. The arguments are all inside the pipeline; final is ignored.
+		return s.evalPipeline(dot, n)
+	case *parse.VariableNode:
+		return s.evalVariableNode(dot, n, cmd.Args, final)
+	}
+	s.at(firstWord)
+	s.notAFunction(cmd.Args, final)
+	switch word := firstWord.(type) {
+	case *parse.BoolNode:
+		return reflect.ValueOf(word.True)
+	case *parse.DotNode:
+		return dot
+	case *parse.NilNode:
+		s.errorf("nil is not a command")
+	case *parse.NumberNode:
+		return s.idealConstant(word)
+	case *parse.StringNode:
+		return reflect.ValueOf(word.Text)
+	}
+	s.errorf("can't evaluate command %q", firstWord)
+	panic("not reached")
+}
+
+// idealConstant is called to return the value of a number in a context where
+// we don't know the type. In that case, the syntax of the number tells us
+// its type, and we use Go rules to resolve.  Note there is no such thing as
+// a uint ideal constant in this situation - the value must be of int type.
+func (s *state) idealConstant(constant *parse.NumberNode) reflect.Value {
+	// These are ideal constants but we don't know the type
+	// and we have no context.  (If it was a method argument,
+	// we'd know what we need.) The syntax guides us to some extent.
+	s.at(constant)
+	switch {
+	case constant.IsComplex:
+		return reflect.ValueOf(constant.Complex128) // incontrovertible.
+	case constant.IsFloat && !isHexConstant(constant.Text) && strings.IndexAny(constant.Text, ".eE") >= 0:
+		return reflect.ValueOf(constant.Float64)
+	case constant.IsInt:
+		n := int(constant.Int64)
+		if int64(n) != constant.Int64 {
+			s.errorf("%s overflows int", constant.Text)
+		}
+		return reflect.ValueOf(n)
+	case constant.IsUint:
+		s.errorf("%s overflows int", constant.Text)
+	}
+	return zero
+}
+
+func isHexConstant(s string) bool {
+	return len(s) > 2 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X')
+}
+
+func (s *state) evalFieldNode(dot reflect.Value, field *parse.FieldNode, args []parse.Node, final reflect.Value) reflect.Value {
+	s.at(field)
+	return s.evalFieldChain(dot, dot, field, field.Ident, args, final)
+}
+
+func (s *state) evalChainNode(dot reflect.Value, chain *parse.ChainNode, args []parse.Node, final reflect.Value) reflect.Value {
+	s.at(chain)
+	// (pipe).Field1.Field2 has pipe as .Node, fields as .Field. Eval the pipeline, then the fields.
+	pipe := s.evalArg(dot, nil, chain.Node)
+	if len(chain.Field) == 0 {
+		s.errorf("internal error: no fields in evalChainNode")
+	}
+	return s.evalFieldChain(dot, pipe, chain, chain.Field, args, final)
+}
+
+func (s *state) evalVariableNode(dot reflect.Value, variable *parse.VariableNode, args []parse.Node, final reflect.Value) reflect.Value {
+	// $x.Field has $x as the first ident, Field as the second. Eval the var, then the fields.
+	s.at(variable)
+	value := s.varValue(variable.Ident[0])
+	if len(variable.Ident) == 1 {
+		s.notAFunction(args, final)
+		return value
+	}
+	return s.evalFieldChain(dot, value, variable, variable.Ident[1:], args, final)
+}
+
+// evalFieldChain evaluates .X.Y.Z possibly followed by arguments.
+// dot is the environment in which to evaluate arguments, while
+// receiver is the value being walked along the chain.
+func (s *state) evalFieldChain(dot, receiver reflect.Value, node parse.Node, ident []string, args []parse.Node, final reflect.Value) reflect.Value {
+	n := len(ident)
+	for i := 0; i < n-1; i++ {
+		receiver = s.evalField(dot, ident[i], node, nil, zero, receiver)
+	}
+	// Now if it's a method, it gets the arguments.
+	return s.evalField(dot, ident[n-1], node, args, final, receiver)
+}
+
+func (s *state) evalFunction(dot reflect.Value, node *parse.IdentifierNode, cmd parse.Node, args []parse.Node, final reflect.Value) reflect.Value {
+	s.at(node)
+	name := node.Ident
+	function, ok := findFunction(name, s.tmpl)
+	if !ok {
+		s.errorf("%q is not a defined function", name)
+	}
+	return s.evalCall(dot, function, cmd, name, args, final)
+}
+
+// evalField evaluates an expression like (.Field) or (.Field arg1 arg2).
+// The 'final' argument represents the return value from the preceding
+// value of the pipeline, if any.
+func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node, args []parse.Node, final, receiver reflect.Value) reflect.Value {
+	if !receiver.IsValid() {
+		return zero
+	}
+	typ := receiver.Type()
+	receiver, _ = indirect(receiver)
+	// Unless it's an interface, need to get to a value of type *T to guarantee
+	// we see all methods of T and *T.
+	ptr := receiver
+	if ptr.Kind() != reflect.Interface && ptr.CanAddr() {
+		ptr = ptr.Addr()
+	}
+	if method := ptr.MethodByName(fieldName); method.IsValid() {
+		return s.evalCall(dot, method, node, fieldName, args, final)
+	}
+	hasArgs := len(args) > 1 || final.IsValid()
+	// It's not a method; must be a field of a struct or an element of a map. The receiver must not be nil.
+	receiver, isNil := indirect(receiver)
+	if isNil {
+		s.errorf("nil pointer evaluating %s.%s", typ, fieldName)
+	}
+	switch receiver.Kind() {
+	case reflect.Struct:
+		tField, ok := receiver.Type().FieldByName(fieldName)
+		if ok {
+			field := receiver.FieldByIndex(tField.Index)
+			if tField.PkgPath != "" { // field is unexported
+				s.errorf("%s is an unexported field of struct type %s", fieldName, typ)
+			}
+			// If it's a function, we must call it.
+			if hasArgs {
+				s.errorf("%s has arguments but cannot be invoked as function", fieldName)
+			}
+			return field
+		}
+		s.errorf("%s is not a field of struct type %s", fieldName, typ)
+	case reflect.Map:
+		// If it's a map, attempt to use the field name as a key.
+		nameVal := reflect.ValueOf(fieldName)
+		if nameVal.Type().AssignableTo(receiver.Type().Key()) {
+			if hasArgs {
+				s.errorf("%s is not a method but has arguments", fieldName)
+			}
+			return receiver.MapIndex(nameVal)
+		}
+	}
+	s.errorf("can't evaluate field %s in type %s", fieldName, typ)
+	panic("not reached")
+}
+
+var (
+	errorType       = reflect.TypeOf((*error)(nil)).Elem()
+	fmtStringerType = reflect.TypeOf((*fmt.Stringer)(nil)).Elem()
+)
+
+// evalCall executes a function or method call. If it's a method, fun already has the receiver bound, so
+// it looks just like a function call.  The arg list, if non-nil, includes (in the manner of the shell), arg[0]
+// as the function itself.
+func (s *state) evalCall(dot, fun reflect.Value, node parse.Node, name string, args []parse.Node, final reflect.Value) reflect.Value {
+	if args != nil {
+		args = args[1:] // Zeroth arg is function name/node; not passed to function.
+	}
+	typ := fun.Type()
+	numIn := len(args)
+	if final.IsValid() {
+		numIn++
+	}
+	numFixed := len(args)
+	if typ.IsVariadic() {
+		numFixed = typ.NumIn() - 1 // last arg is the variadic one.
+		if numIn < numFixed {
+			s.errorf("wrong number of args for %s: want at least %d got %d", name, typ.NumIn()-1, len(args))
+		}
+	} else if numIn < typ.NumIn()-1 || !typ.IsVariadic() && numIn != typ.NumIn() {
+		s.errorf("wrong number of args for %s: want %d got %d", name, typ.NumIn(), len(args))
+	}
+	if !goodFunc(typ) {
+		// TODO: This could still be a confusing error; maybe goodFunc should provide info.
+		s.errorf("can't call method/function %q with %d results", name, typ.NumOut())
+	}
+	// Build the arg list.
+	argv := make([]reflect.Value, numIn)
+	// Args must be evaluated. Fixed args first.
+	i := 0
+	for ; i < numFixed; i++ {
+		argv[i] = s.evalArg(dot, typ.In(i), args[i])
+	}
+	// Now the ... args.
+	if typ.IsVariadic() {
+		argType := typ.In(typ.NumIn() - 1).Elem() // Argument is a slice.
+		for ; i < len(args); i++ {
+			argv[i] = s.evalArg(dot, argType, args[i])
+		}
+	}
+	// Add final value if necessary.
+	if final.IsValid() {
+		t := typ.In(typ.NumIn() - 1)
+		if typ.IsVariadic() {
+			t = t.Elem()
+		}
+		argv[i] = s.validateType(final, t)
+	}
+	result := fun.Call(argv)
+	// If we have an error that is not nil, stop execution and return that error to the caller.
+	if len(result) == 2 && !result[1].IsNil() {
+		s.at(node)
+		s.errorf("error calling %s: %s", name, result[1].Interface().(error))
+	}
+	return result[0]
+}
+
+// canBeNil reports whether an untyped nil can be assigned to the type. See reflect.Zero.
+func canBeNil(typ reflect.Type) bool {
+	switch typ.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Ptr, reflect.Slice:
+		return true
+	}
+	return false
+}
+
+// validateType guarantees that the value is valid and assignable to the type.
+func (s *state) validateType(value reflect.Value, typ reflect.Type) reflect.Value {
+	if !value.IsValid() {
+		if typ == nil || canBeNil(typ) {
+			// An untyped nil interface{}. Accept as a proper nil value.
+			return reflect.Zero(typ)
+		}
+		s.errorf("invalid value; expected %s", typ)
+	}
+	if typ != nil && !value.Type().AssignableTo(typ) {
+		if value.Kind() == reflect.Interface && !value.IsNil() {
+			value = value.Elem()
+			if value.Type().AssignableTo(typ) {
+				return value
+			}
+			// fallthrough
+		}
+		// Does one dereference or indirection work? We could do more, as we
+		// do with method receivers, but that gets messy and method receivers
+		// are much more constrained, so it makes more sense there than here.
+		// Besides, one is almost always all you need.
+		switch {
+		case value.Kind() == reflect.Ptr && value.Type().Elem().AssignableTo(typ):
+			value = value.Elem()
+			if !value.IsValid() {
+				s.errorf("dereference of nil pointer of type %s", typ)
+			}
+		case reflect.PtrTo(value.Type()).AssignableTo(typ) && value.CanAddr():
+			value = value.Addr()
+		default:
+			s.errorf("wrong type for value; expected %s; got %s", typ, value.Type())
+		}
+	}
+	return value
+}
+
+func (s *state) evalArg(dot reflect.Value, typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	switch arg := n.(type) {
+	case *parse.DotNode:
+		return s.validateType(dot, typ)
+	case *parse.NilNode:
+		if canBeNil(typ) {
+			return reflect.Zero(typ)
+		}
+		s.errorf("cannot assign nil to %s", typ)
+	case *parse.FieldNode:
+		return s.validateType(s.evalFieldNode(dot, arg, []parse.Node{n}, zero), typ)
+	case *parse.VariableNode:
+		return s.validateType(s.evalVariableNode(dot, arg, nil, zero), typ)
+	case *parse.PipeNode:
+		return s.validateType(s.evalPipeline(dot, arg), typ)
+	case *parse.IdentifierNode:
+		return s.evalFunction(dot, arg, arg, nil, zero)
+	}
+	switch typ.Kind() {
+	case reflect.Bool:
+		return s.evalBool(typ, n)
+	case reflect.Complex64, reflect.Complex128:
+		return s.evalComplex(typ, n)
+	case reflect.Float32, reflect.Float64:
+		return s.evalFloat(typ, n)
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return s.evalInteger(typ, n)
+	case reflect.Interface:
+		if typ.NumMethod() == 0 {
+			return s.evalEmptyInterface(dot, n)
+		}
+	case reflect.String:
+		return s.evalString(typ, n)
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return s.evalUnsignedInteger(typ, n)
+	}
+	s.errorf("can't handle %s for arg of type %s", n, typ)
+	panic("not reached")
+}
+
+func (s *state) evalBool(typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	if n, ok := n.(*parse.BoolNode); ok {
+		value := reflect.New(typ).Elem()
+		value.SetBool(n.True)
+		return value
+	}
+	s.errorf("expected bool; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalString(typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	if n, ok := n.(*parse.StringNode); ok {
+		value := reflect.New(typ).Elem()
+		value.SetString(n.Text)
+		return value
+	}
+	s.errorf("expected string; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalInteger(typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	if n, ok := n.(*parse.NumberNode); ok && n.IsInt {
+		value := reflect.New(typ).Elem()
+		value.SetInt(n.Int64)
+		return value
+	}
+	s.errorf("expected integer; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalUnsignedInteger(typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	if n, ok := n.(*parse.NumberNode); ok && n.IsUint {
+		value := reflect.New(typ).Elem()
+		value.SetUint(n.Uint64)
+		return value
+	}
+	s.errorf("expected unsigned integer; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalFloat(typ reflect.Type, n parse.Node) reflect.Value {
+	s.at(n)
+	if n, ok := n.(*parse.NumberNode); ok && n.IsFloat {
+		value := reflect.New(typ).Elem()
+		value.SetFloat(n.Float64)
+		return value
+	}
+	s.errorf("expected float; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalComplex(typ reflect.Type, n parse.Node) reflect.Value {
+	if n, ok := n.(*parse.NumberNode); ok && n.IsComplex {
+		value := reflect.New(typ).Elem()
+		value.SetComplex(n.Complex128)
+		return value
+	}
+	s.errorf("expected complex; found %s", n)
+	panic("not reached")
+}
+
+func (s *state) evalEmptyInterface(dot reflect.Value, n parse.Node) reflect.Value {
+	s.at(n)
+	switch n := n.(type) {
+	case *parse.BoolNode:
+		return reflect.ValueOf(n.True)
+	case *parse.DotNode:
+		return dot
+	case *parse.FieldNode:
+		return s.evalFieldNode(dot, n, nil, zero)
+	case *parse.IdentifierNode:
+		return s.evalFunction(dot, n, n, nil, zero)
+	case *parse.NilNode:
+		// NilNode is handled in evalArg, the only place that calls here.
+		s.errorf("evalEmptyInterface: nil (can't happen)")
+	case *parse.NumberNode:
+		return s.idealConstant(n)
+	case *parse.StringNode:
+		return reflect.ValueOf(n.Text)
+	case *parse.VariableNode:
+		return s.evalVariableNode(dot, n, nil, zero)
+	case *parse.PipeNode:
+		return s.evalPipeline(dot, n)
+	}
+	s.errorf("can't handle assignment of %s to empty interface argument", n)
+	panic("not reached")
+}
+
+// indirect returns the item at the end of indirection, and a bool to indicate if it's nil.
+// We indirect through pointers and empty interfaces (only) because
+// non-empty interfaces have methods we might need.
+func indirect(v reflect.Value) (rv reflect.Value, isNil bool) {
+	for ; v.Kind() == reflect.Ptr || v.Kind() == reflect.Interface; v = v.Elem() {
+		if v.IsNil() {
+			return v, true
+		}
+		if v.Kind() == reflect.Interface && v.NumMethod() > 0 {
+			break
+		}
+	}
+	return v, false
+}
+
+// printValue writes the textual representation of the value to the output of
+// the template.
+func (s *state) printValue(n parse.Node, v reflect.Value) {
+	s.at(n)
+	iface, ok := printableValue(v)
+	if !ok {
+		s.errorf("can't print %s of type %s", n, v.Type())
+	}
+	fmt.Fprint(s.wr, iface)
+}
+
+// printableValue returns the, possibly indirected, interface value inside v that
+// is best for a call to formatted printer.
+func printableValue(v reflect.Value) (interface{}, bool) {
+	if v.Kind() == reflect.Ptr {
+		v, _ = indirect(v) // fmt.Fprint handles nil.
+	}
+	if !v.IsValid() {
+		return "<no value>", true
+	}
+
+	if !v.Type().Implements(errorType) && !v.Type().Implements(fmtStringerType) {
+		if v.CanAddr() && (reflect.PtrTo(v.Type()).Implements(errorType) || reflect.PtrTo(v.Type()).Implements(fmtStringerType)) {
+			v = v.Addr()
+		} else {
+			switch v.Kind() {
+			case reflect.Chan, reflect.Func:
+				return nil, false
+			}
+		}
+	}
+	return v.Interface(), true
+}
+
+// Types to help sort the keys in a map for reproducible output.
+
+type rvs []reflect.Value
+
+func (x rvs) Len() int      { return len(x) }
+func (x rvs) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
+
+type rvInts struct{ rvs }
+
+func (x rvInts) Less(i, j int) bool { return x.rvs[i].Int() < x.rvs[j].Int() }
+
+type rvUints struct{ rvs }
+
+func (x rvUints) Less(i, j int) bool { return x.rvs[i].Uint() < x.rvs[j].Uint() }
+
+type rvFloats struct{ rvs }
+
+func (x rvFloats) Less(i, j int) bool { return x.rvs[i].Float() < x.rvs[j].Float() }
+
+type rvStrings struct{ rvs }
+
+func (x rvStrings) Less(i, j int) bool { return x.rvs[i].String() < x.rvs[j].String() }
+
+// sortKeys sorts (if it can) the slice of reflect.Values, which is a slice of map keys.
+func sortKeys(v []reflect.Value) []reflect.Value {
+	if len(v) <= 1 {
+		return v
+	}
+	switch v[0].Kind() {
+	case reflect.Float32, reflect.Float64:
+		sort.Sort(rvFloats{v})
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		sort.Sort(rvInts{v})
+	case reflect.String:
+		sort.Sort(rvStrings{v})
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		sort.Sort(rvUints{v})
+	}
+	return v
+}
diff --git a/src/text/template/exec_test.go b/src/text/template/exec_test.go
new file mode 100644
index 000000000..663aaf3af
--- /dev/null
+++ b/src/text/template/exec_test.go
@@ -0,0 +1,994 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+var debug = flag.Bool("debug", false, "show the errors produced by the tests")
+
+// T has lots of interesting pieces to use to test execution.
+type T struct {
+	// Basics
+	True        bool
+	I           int
+	U16         uint16
+	X           string
+	FloatZero   float64
+	ComplexZero complex128
+	// Nested structs.
+	U *U
+	// Struct with String method.
+	V0     V
+	V1, V2 *V
+	// Struct with Error method.
+	W0     W
+	W1, W2 *W
+	// Slices
+	SI      []int
+	SIEmpty []int
+	SB      []bool
+	// Maps
+	MSI      map[string]int
+	MSIone   map[string]int // one element, for deterministic output
+	MSIEmpty map[string]int
+	MXI      map[interface{}]int
+	MII      map[int]int
+	SMSI     []map[string]int
+	// Empty interfaces; used to see if we can dig inside one.
+	Empty0 interface{} // nil
+	Empty1 interface{}
+	Empty2 interface{}
+	Empty3 interface{}
+	Empty4 interface{}
+	// Non-empty interface.
+	NonEmptyInterface I
+	// Stringer.
+	Str fmt.Stringer
+	Err error
+	// Pointers
+	PI  *int
+	PS  *string
+	PSI *[]int
+	NIL *int
+	// Function (not method)
+	BinaryFunc      func(string, string) string
+	VariadicFunc    func(...string) string
+	VariadicFuncInt func(int, ...string) string
+	NilOKFunc       func(*int) bool
+	ErrFunc         func() (string, error)
+	// Template to test evaluation of templates.
+	Tmpl *Template
+	// Unexported field; cannot be accessed by template.
+	unexported int
+}
+
+type U struct {
+	V string
+}
+
+type V struct {
+	j int
+}
+
+func (v *V) String() string {
+	if v == nil {
+		return "nilV"
+	}
+	return fmt.Sprintf("<%d>", v.j)
+}
+
+type W struct {
+	k int
+}
+
+func (w *W) Error() string {
+	if w == nil {
+		return "nilW"
+	}
+	return fmt.Sprintf("[%d]", w.k)
+}
+
+var tVal = &T{
+	True:   true,
+	I:      17,
+	U16:    16,
+	X:      "x",
+	U:      &U{"v"},
+	V0:     V{6666},
+	V1:     &V{7777}, // leave V2 as nil
+	W0:     W{888},
+	W1:     &W{999}, // leave W2 as nil
+	SI:     []int{3, 4, 5},
+	SB:     []bool{true, false},
+	MSI:    map[string]int{"one": 1, "two": 2, "three": 3},
+	MSIone: map[string]int{"one": 1},
+	MXI:    map[interface{}]int{"one": 1},
+	MII:    map[int]int{1: 1},
+	SMSI: []map[string]int{
+		{"one": 1, "two": 2},
+		{"eleven": 11, "twelve": 12},
+	},
+	Empty1:            3,
+	Empty2:            "empty2",
+	Empty3:            []int{7, 8},
+	Empty4:            &U{"UinEmpty"},
+	NonEmptyInterface: new(T),
+	Str:               bytes.NewBuffer([]byte("foozle")),
+	Err:               errors.New("erroozle"),
+	PI:                newInt(23),
+	PS:                newString("a string"),
+	PSI:               newIntSlice(21, 22, 23),
+	BinaryFunc:        func(a, b string) string { return fmt.Sprintf("[%s=%s]", a, b) },
+	VariadicFunc:      func(s ...string) string { return fmt.Sprint("<", strings.Join(s, "+"), ">") },
+	VariadicFuncInt:   func(a int, s ...string) string { return fmt.Sprint(a, "=<", strings.Join(s, "+"), ">") },
+	NilOKFunc:         func(s *int) bool { return s == nil },
+	ErrFunc:           func() (string, error) { return "bla", nil },
+	Tmpl:              Must(New("x").Parse("test template")), // "x" is the value of .X
+}
+
+// A non-empty interface.
+type I interface {
+	Method0() string
+}
+
+var iVal I = tVal
+
+// Helpers for creation.
+func newInt(n int) *int {
+	return &n
+}
+
+func newString(s string) *string {
+	return &s
+}
+
+func newIntSlice(n ...int) *[]int {
+	p := new([]int)
+	*p = make([]int, len(n))
+	copy(*p, n)
+	return p
+}
+
+// Simple methods with and without arguments.
+func (t *T) Method0() string {
+	return "M0"
+}
+
+func (t *T) Method1(a int) int {
+	return a
+}
+
+func (t *T) Method2(a uint16, b string) string {
+	return fmt.Sprintf("Method2: %d %s", a, b)
+}
+
+func (t *T) Method3(v interface{}) string {
+	return fmt.Sprintf("Method3: %v", v)
+}
+
+func (t *T) MAdd(a int, b []int) []int {
+	v := make([]int, len(b))
+	for i, x := range b {
+		v[i] = x + a
+	}
+	return v
+}
+
+var myError = errors.New("my error")
+
+// MyError returns a value and an error according to its argument.
+func (t *T) MyError(error bool) (bool, error) {
+	if error {
+		return true, myError
+	}
+	return false, nil
+}
+
+// A few methods to test chaining.
+func (t *T) GetU() *U {
+	return t.U
+}
+
+func (u *U) TrueFalse(b bool) string {
+	if b {
+		return "true"
+	}
+	return ""
+}
+
+func typeOf(arg interface{}) string {
+	return fmt.Sprintf("%T", arg)
+}
+
+type execTest struct {
+	name   string
+	input  string
+	output string
+	data   interface{}
+	ok     bool
+}
+
+// bigInt and bigUint are hex string representing numbers either side
+// of the max int boundary.
+// We do it this way so the test doesn't depend on ints being 32 bits.
+var (
+	bigInt  = fmt.Sprintf("0x%x", int(1<<uint(reflect.TypeOf(0).Bits()-1)-1))
+	bigUint = fmt.Sprintf("0x%x", uint(1<<uint(reflect.TypeOf(0).Bits()-1)))
+)
+
+var execTests = []execTest{
+	// Trivial cases.
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+	{"nil action", "{{nil}}", "", nil, false},
+
+	// Ideal constants.
+	{"ideal int", "{{typeOf 3}}", "int", 0, true},
+	{"ideal float", "{{typeOf 1.0}}", "float64", 0, true},
+	{"ideal exp float", "{{typeOf 1e1}}", "float64", 0, true},
+	{"ideal complex", "{{typeOf 1i}}", "complex128", 0, true},
+	{"ideal int", "{{typeOf " + bigInt + "}}", "int", 0, true},
+	{"ideal too big", "{{typeOf " + bigUint + "}}", "", 0, false},
+	{"ideal nil without type", "{{nil}}", "", 0, false},
+
+	// Fields of structs.
+	{".X", "-{{.X}}-", "-x-", tVal, true},
+	{".U.V", "-{{.U.V}}-", "-v-", tVal, true},
+	{".unexported", "{{.unexported}}", "", tVal, false},
+
+	// Fields on maps.
+	{"map .one", "{{.MSI.one}}", "1", tVal, true},
+	{"map .two", "{{.MSI.two}}", "2", tVal, true},
+	{"map .NO", "{{.MSI.NO}}", "<no value>", tVal, true},
+	{"map .one interface", "{{.MXI.one}}", "1", tVal, true},
+	{"map .WRONG args", "{{.MSI.one 1}}", "", tVal, false},
+	{"map .WRONG type", "{{.MII.one}}", "", tVal, false},
+
+	// Dots of all kinds to test basic evaluation.
+	{"dot int", "<{{.}}>", "<13>", 13, true},
+	{"dot uint", "<{{.}}>", "<14>", uint(14), true},
+	{"dot float", "<{{.}}>", "<15.1>", 15.1, true},
+	{"dot bool", "<{{.}}>", "<true>", true, true},
+	{"dot complex", "<{{.}}>", "<(16.2-17i)>", 16.2 - 17i, true},
+	{"dot string", "<{{.}}>", "<hello>", "hello", true},
+	{"dot slice", "<{{.}}>", "<[-1 -2 -3]>", []int{-1, -2, -3}, true},
+	{"dot map", "<{{.}}>", "<map[two:22]>", map[string]int{"two": 22}, true},
+	{"dot struct", "<{{.}}>", "<{7 seven}>", struct {
+		a int
+		b string
+	}{7, "seven"}, true},
+
+	// Variables.
+	{"$ int", "{{$}}", "123", 123, true},
+	{"$.I", "{{$.I}}", "17", tVal, true},
+	{"$.U.V", "{{$.U.V}}", "v", tVal, true},
+	{"declare in action", "{{$x := $.U.V}}{{$x}}", "v", tVal, true},
+
+	// Type with String method.
+	{"V{6666}.String()", "-{{.V0}}-", "-<6666>-", tVal, true},
+	{"&V{7777}.String()", "-{{.V1}}-", "-<7777>-", tVal, true},
+	{"(*V)(nil).String()", "-{{.V2}}-", "-nilV-", tVal, true},
+
+	// Type with Error method.
+	{"W{888}.Error()", "-{{.W0}}-", "-[888]-", tVal, true},
+	{"&W{999}.Error()", "-{{.W1}}-", "-[999]-", tVal, true},
+	{"(*W)(nil).Error()", "-{{.W2}}-", "-nilW-", tVal, true},
+
+	// Pointers.
+	{"*int", "{{.PI}}", "23", tVal, true},
+	{"*string", "{{.PS}}", "a string", tVal, true},
+	{"*[]int", "{{.PSI}}", "[21 22 23]", tVal, true},
+	{"*[]int[1]", "{{index .PSI 1}}", "22", tVal, true},
+	{"NIL", "{{.NIL}}", "<nil>", tVal, true},
+
+	// Empty interfaces holding values.
+	{"empty nil", "{{.Empty0}}", "<no value>", tVal, true},
+	{"empty with int", "{{.Empty1}}", "3", tVal, true},
+	{"empty with string", "{{.Empty2}}", "empty2", tVal, true},
+	{"empty with slice", "{{.Empty3}}", "[7 8]", tVal, true},
+	{"empty with struct", "{{.Empty4}}", "{UinEmpty}", tVal, true},
+	{"empty with struct, field", "{{.Empty4.V}}", "UinEmpty", tVal, true},
+
+	// Method calls.
+	{".Method0", "-{{.Method0}}-", "-M0-", tVal, true},
+	{".Method1(1234)", "-{{.Method1 1234}}-", "-1234-", tVal, true},
+	{".Method1(.I)", "-{{.Method1 .I}}-", "-17-", tVal, true},
+	{".Method2(3, .X)", "-{{.Method2 3 .X}}-", "-Method2: 3 x-", tVal, true},
+	{".Method2(.U16, `str`)", "-{{.Method2 .U16 `str`}}-", "-Method2: 16 str-", tVal, true},
+	{".Method2(.U16, $x)", "{{if $x := .X}}-{{.Method2 .U16 $x}}{{end}}-", "-Method2: 16 x-", tVal, true},
+	{".Method3(nil constant)", "-{{.Method3 nil}}-", "-Method3: <nil>-", tVal, true},
+	{".Method3(nil value)", "-{{.Method3 .MXI.unset}}-", "-Method3: <nil>-", tVal, true},
+	{"method on var", "{{if $x := .}}-{{$x.Method2 .U16 $x.X}}{{end}}-", "-Method2: 16 x-", tVal, true},
+	{"method on chained var",
+		"{{range .MSIone}}{{if $.U.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
+		"true", tVal, true},
+	{"chained method",
+		"{{range .MSIone}}{{if $.GetU.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
+		"true", tVal, true},
+	{"chained method on variable",
+		"{{with $x := .}}{{with .SI}}{{$.GetU.TrueFalse $.True}}{{end}}{{end}}",
+		"true", tVal, true},
+	{".NilOKFunc not nil", "{{call .NilOKFunc .PI}}", "false", tVal, true},
+	{".NilOKFunc nil", "{{call .NilOKFunc nil}}", "true", tVal, true},
+
+	// Function call builtin.
+	{".BinaryFunc", "{{call .BinaryFunc `1` `2`}}", "[1=2]", tVal, true},
+	{".VariadicFunc0", "{{call .VariadicFunc}}", "<>", tVal, true},
+	{".VariadicFunc2", "{{call .VariadicFunc `he` `llo`}}", "<he+llo>", tVal, true},
+	{".VariadicFuncInt", "{{call .VariadicFuncInt 33 `he` `llo`}}", "33=<he+llo>", tVal, true},
+	{"if .BinaryFunc call", "{{ if .BinaryFunc}}{{call .BinaryFunc `1` `2`}}{{end}}", "[1=2]", tVal, true},
+	{"if not .BinaryFunc call", "{{ if not .BinaryFunc}}{{call .BinaryFunc `1` `2`}}{{else}}No{{end}}", "No", tVal, true},
+	{"Interface Call", `{{stringer .S}}`, "foozle", map[string]interface{}{"S": bytes.NewBufferString("foozle")}, true},
+	{".ErrFunc", "{{call .ErrFunc}}", "bla", tVal, true},
+
+	// Erroneous function calls (check args).
+	{".BinaryFuncTooFew", "{{call .BinaryFunc `1`}}", "", tVal, false},
+	{".BinaryFuncTooMany", "{{call .BinaryFunc `1` `2` `3`}}", "", tVal, false},
+	{".BinaryFuncBad0", "{{call .BinaryFunc 1 3}}", "", tVal, false},
+	{".BinaryFuncBad1", "{{call .BinaryFunc `1` 3}}", "", tVal, false},
+	{".VariadicFuncBad0", "{{call .VariadicFunc 3}}", "", tVal, false},
+	{".VariadicFuncIntBad0", "{{call .VariadicFuncInt}}", "", tVal, false},
+	{".VariadicFuncIntBad`", "{{call .VariadicFuncInt `x`}}", "", tVal, false},
+	{".VariadicFuncNilBad", "{{call .VariadicFunc nil}}", "", tVal, false},
+
+	// Pipelines.
+	{"pipeline", "-{{.Method0 | .Method2 .U16}}-", "-Method2: 16 M0-", tVal, true},
+	{"pipeline func", "-{{call .VariadicFunc `llo` | call .VariadicFunc `he` }}-", "-<he+<llo>>-", tVal, true},
+
+	// Parenthesized expressions
+	{"parens in pipeline", "{{printf `%d %d %d` (1) (2 | add 3) (add 4 (add 5 6))}}", "1 5 15", tVal, true},
+
+	// Parenthesized expressions with field accesses
+	{"parens: $ in paren", "{{($).X}}", "x", tVal, true},
+	{"parens: $.GetU in paren", "{{($.GetU).V}}", "v", tVal, true},
+	{"parens: $ in paren in pipe", "{{($ | echo).X}}", "x", tVal, true},
+	{"parens: spaces and args", `{{(makemap "up" "down" "left" "right").left}}`, "right", tVal, true},
+
+	// If.
+	{"if true", "{{if true}}TRUE{{end}}", "TRUE", tVal, true},
+	{"if false", "{{if false}}TRUE{{else}}FALSE{{end}}", "FALSE", tVal, true},
+	{"if nil", "{{if nil}}TRUE{{end}}", "", tVal, false},
+	{"if 1", "{{if 1}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0", "{{if 0}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if 1.5", "{{if 1.5}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0.0", "{{if .FloatZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if 1.5i", "{{if 1.5i}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
+	{"if 0.0i", "{{if .ComplexZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if emptystring", "{{if ``}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if string", "{{if `notempty`}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if emptyslice", "{{if .SIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if slice", "{{if .SI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if emptymap", "{{if .MSIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"if map", "{{if .MSI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
+	{"if map unset", "{{if .MXI.none}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"if map not unset", "{{if not .MXI.none}}ZERO{{else}}NON-ZERO{{end}}", "ZERO", tVal, true},
+	{"if $x with $y int", "{{if $x := true}}{{with $y := .I}}{{$x}},{{$y}}{{end}}{{end}}", "true,17", tVal, true},
+	{"if $x with $x int", "{{if $x := true}}{{with $x := .I}}{{$x}},{{end}}{{$x}}{{end}}", "17,true", tVal, true},
+	{"if else if", "{{if false}}FALSE{{else if true}}TRUE{{end}}", "TRUE", tVal, true},
+	{"if else chain", "{{if eq 1 3}}1{{else if eq 2 3}}2{{else if eq 3 3}}3{{end}}", "3", tVal, true},
+
+	// Print etc.
+	{"print", `{{print "hello, print"}}`, "hello, print", tVal, true},
+	{"print 123", `{{print 1 2 3}}`, "1 2 3", tVal, true},
+	{"print nil", `{{print nil}}`, "<nil>", tVal, true},
+	{"println", `{{println 1 2 3}}`, "1 2 3\n", tVal, true},
+	{"printf int", `{{printf "%04x" 127}}`, "007f", tVal, true},
+	{"printf float", `{{printf "%g" 3.5}}`, "3.5", tVal, true},
+	{"printf complex", `{{printf "%g" 1+7i}}`, "(1+7i)", tVal, true},
+	{"printf string", `{{printf "%s" "hello"}}`, "hello", tVal, true},
+	{"printf function", `{{printf "%#q" zeroArgs}}`, "`zeroArgs`", tVal, true},
+	{"printf field", `{{printf "%s" .U.V}}`, "v", tVal, true},
+	{"printf method", `{{printf "%s" .Method0}}`, "M0", tVal, true},
+	{"printf dot", `{{with .I}}{{printf "%d" .}}{{end}}`, "17", tVal, true},
+	{"printf var", `{{with $x := .I}}{{printf "%d" $x}}{{end}}`, "17", tVal, true},
+	{"printf lots", `{{printf "%d %s %g %s" 127 "hello" 7-3i .Method0}}`, "127 hello (7-3i) M0", tVal, true},
+
+	// HTML.
+	{"html", `{{html "<script>alert(\"XSS\");</script>"}}`,
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
+	{"html pipeline", `{{printf "<script>alert(\"XSS\");</script>" | html}}`,
+		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
+	{"html", `{{html .PS}}`, "a string", tVal, true},
+
+	// JavaScript.
+	{"js", `{{js .}}`, `It\'d be nice.`, `It'd be nice.`, true},
+
+	// URL query.
+	{"urlquery", `{{"http://www.example.org/"|urlquery}}`, "http%3A%2F%2Fwww.example.org%2F", nil, true},
+
+	// Booleans
+	{"not", "{{not true}} {{not false}}", "false true", nil, true},
+	{"and", "{{and false 0}} {{and 1 0}} {{and 0 true}} {{and 1 1}}", "false 0 0 1", nil, true},
+	{"or", "{{or 0 0}} {{or 1 0}} {{or 0 true}} {{or 1 1}}", "0 1 true 1", nil, true},
+	{"boolean if", "{{if and true 1 `hi`}}TRUE{{else}}FALSE{{end}}", "TRUE", tVal, true},
+	{"boolean if not", "{{if and true 1 `hi` | not}}TRUE{{else}}FALSE{{end}}", "FALSE", nil, true},
+
+	// Indexing.
+	{"slice[0]", "{{index .SI 0}}", "3", tVal, true},
+	{"slice[1]", "{{index .SI 1}}", "4", tVal, true},
+	{"slice[HUGE]", "{{index .SI 10}}", "", tVal, false},
+	{"slice[WRONG]", "{{index .SI `hello`}}", "", tVal, false},
+	{"map[one]", "{{index .MSI `one`}}", "1", tVal, true},
+	{"map[two]", "{{index .MSI `two`}}", "2", tVal, true},
+	{"map[NO]", "{{index .MSI `XXX`}}", "0", tVal, true},
+	{"map[nil]", "{{index .MSI nil}}", "0", tVal, true},
+	{"map[WRONG]", "{{index .MSI 10}}", "", tVal, false},
+	{"double index", "{{index .SMSI 1 `eleven`}}", "11", tVal, true},
+
+	// Len.
+	{"slice", "{{len .SI}}", "3", tVal, true},
+	{"map", "{{len .MSI }}", "3", tVal, true},
+	{"len of int", "{{len 3}}", "", tVal, false},
+	{"len of nothing", "{{len .Empty0}}", "", tVal, false},
+
+	// With.
+	{"with true", "{{with true}}{{.}}{{end}}", "true", tVal, true},
+	{"with false", "{{with false}}{{.}}{{else}}FALSE{{end}}", "FALSE", tVal, true},
+	{"with 1", "{{with 1}}{{.}}{{else}}ZERO{{end}}", "1", tVal, true},
+	{"with 0", "{{with 0}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with 1.5", "{{with 1.5}}{{.}}{{else}}ZERO{{end}}", "1.5", tVal, true},
+	{"with 0.0", "{{with .FloatZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with 1.5i", "{{with 1.5i}}{{.}}{{else}}ZERO{{end}}", "(0+1.5i)", tVal, true},
+	{"with 0.0i", "{{with .ComplexZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
+	{"with emptystring", "{{with ``}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with string", "{{with `notempty`}}{{.}}{{else}}EMPTY{{end}}", "notempty", tVal, true},
+	{"with emptyslice", "{{with .SIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with slice", "{{with .SI}}{{.}}{{else}}EMPTY{{end}}", "[3 4 5]", tVal, true},
+	{"with emptymap", "{{with .MSIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true},
+	{"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "UinEmpty", tVal, true},
+	{"with $x int", "{{with $x := .I}}{{$x}}{{end}}", "17", tVal, true},
+	{"with $x struct.U.V", "{{with $x := $}}{{$x.U.V}}{{end}}", "v", tVal, true},
+	{"with variable and action", "{{with $x := $}}{{$y := $.U.V}}{{$y}}{{end}}", "v", tVal, true},
+
+	// Range.
+	{"range []int", "{{range .SI}}-{{.}}-{{end}}", "-3--4--5-", tVal, true},
+	{"range empty no else", "{{range .SIEmpty}}-{{.}}-{{end}}", "", tVal, true},
+	{"range []int else", "{{range .SI}}-{{.}}-{{else}}EMPTY{{end}}", "-3--4--5-", tVal, true},
+	{"range empty else", "{{range .SIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"range []bool", "{{range .SB}}-{{.}}-{{end}}", "-true--false-", tVal, true},
+	{"range []int method", "{{range .SI | .MAdd .I}}-{{.}}-{{end}}", "-20--21--22-", tVal, true},
+	{"range map", "{{range .MSI}}-{{.}}-{{end}}", "-1--3--2-", tVal, true},
+	{"range empty map no else", "{{range .MSIEmpty}}-{{.}}-{{end}}", "", tVal, true},
+	{"range map else", "{{range .MSI}}-{{.}}-{{else}}EMPTY{{end}}", "-1--3--2-", tVal, true},
+	{"range empty map else", "{{range .MSIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
+	{"range empty interface", "{{range .Empty3}}-{{.}}-{{else}}EMPTY{{end}}", "-7--8-", tVal, true},
+	{"range empty nil", "{{range .Empty0}}-{{.}}-{{end}}", "", tVal, true},
+	{"range $x SI", "{{range $x := .SI}}<{{$x}}>{{end}}", "<3><4><5>", tVal, true},
+	{"range $x $y SI", "{{range $x, $y := .SI}}<{{$x}}={{$y}}>{{end}}", "<0=3><1=4><2=5>", tVal, true},
+	{"range $x MSIone", "{{range $x := .MSIone}}<{{$x}}>{{end}}", "<1>", tVal, true},
+	{"range $x $y MSIone", "{{range $x, $y := .MSIone}}<{{$x}}={{$y}}>{{end}}", "<one=1>", tVal, true},
+	{"range $x PSI", "{{range $x := .PSI}}<{{$x}}>{{end}}", "<21><22><23>", tVal, true},
+	{"declare in range", "{{range $x := .PSI}}<{{$foo:=$x}}{{$x}}>{{end}}", "<21><22><23>", tVal, true},
+	{"range count", `{{range $i, $x := count 5}}[{{$i}}]{{$x}}{{end}}`, "[0]a[1]b[2]c[3]d[4]e", tVal, true},
+	{"range nil count", `{{range $i, $x := count 0}}{{else}}empty{{end}}`, "empty", tVal, true},
+
+	// Cute examples.
+	{"or as if true", `{{or .SI "slice is empty"}}`, "[3 4 5]", tVal, true},
+	{"or as if false", `{{or .SIEmpty "slice is empty"}}`, "slice is empty", tVal, true},
+
+	// Error handling.
+	{"error method, error", "{{.MyError true}}", "", tVal, false},
+	{"error method, no error", "{{.MyError false}}", "false", tVal, true},
+
+	// Fixed bugs.
+	// Must separate dot and receiver; otherwise args are evaluated with dot set to variable.
+	{"bug0", "{{range .MSIone}}{{if $.Method1 .}}X{{end}}{{end}}", "X", tVal, true},
+	// Do not loop endlessly in indirect for non-empty interfaces.
+	// The bug appears with *interface only; looped forever.
+	{"bug1", "{{.Method0}}", "M0", &iVal, true},
+	// Was taking address of interface field, so method set was empty.
+	{"bug2", "{{$.NonEmptyInterface.Method0}}", "M0", tVal, true},
+	// Struct values were not legal in with - mere oversight.
+	{"bug3", "{{with $}}{{.Method0}}{{end}}", "M0", tVal, true},
+	// Nil interface values in if.
+	{"bug4", "{{if .Empty0}}non-nil{{else}}nil{{end}}", "nil", tVal, true},
+	// Stringer.
+	{"bug5", "{{.Str}}", "foozle", tVal, true},
+	{"bug5a", "{{.Err}}", "erroozle", tVal, true},
+	// Args need to be indirected and dereferenced sometimes.
+	{"bug6a", "{{vfunc .V0 .V1}}", "vfunc", tVal, true},
+	{"bug6b", "{{vfunc .V0 .V0}}", "vfunc", tVal, true},
+	{"bug6c", "{{vfunc .V1 .V0}}", "vfunc", tVal, true},
+	{"bug6d", "{{vfunc .V1 .V1}}", "vfunc", tVal, true},
+	// Legal parse but illegal execution: non-function should have no arguments.
+	{"bug7a", "{{3 2}}", "", tVal, false},
+	{"bug7b", "{{$x := 1}}{{$x 2}}", "", tVal, false},
+	{"bug7c", "{{$x := 1}}{{3 | $x}}", "", tVal, false},
+	// Pipelined arg was not being type-checked.
+	{"bug8a", "{{3|oneArg}}", "", tVal, false},
+	{"bug8b", "{{4|dddArg 3}}", "", tVal, false},
+	// A bug was introduced that broke map lookups for lower-case names.
+	{"bug9", "{{.cause}}", "neglect", map[string]string{"cause": "neglect"}, true},
+	// Field chain starting with function did not work.
+	{"bug10", "{{mapOfThree.three}}-{{(mapOfThree).three}}", "3-3", 0, true},
+	// Dereferencing nil pointer while evaluating function arguments should not panic. Issue 7333.
+	{"bug11", "{{valueString .PS}}", "", T{}, false},
+	// 0xef gave constant type float64. Issue 8622.
+	{"bug12xe", "{{printf `%T` 0xef}}", "int", T{}, true},
+	{"bug12xE", "{{printf `%T` 0xEE}}", "int", T{}, true},
+	{"bug12Xe", "{{printf `%T` 0Xef}}", "int", T{}, true},
+	{"bug12XE", "{{printf `%T` 0XEE}}", "int", T{}, true},
+}
+
+func zeroArgs() string {
+	return "zeroArgs"
+}
+
+func oneArg(a string) string {
+	return "oneArg=" + a
+}
+
+func dddArg(a int, b ...string) string {
+	return fmt.Sprintln(a, b)
+}
+
+// count returns a channel that will deliver n sequential 1-letter strings starting at "a"
+func count(n int) chan string {
+	if n == 0 {
+		return nil
+	}
+	c := make(chan string)
+	go func() {
+		for i := 0; i < n; i++ {
+			c <- "abcdefghijklmnop"[i : i+1]
+		}
+		close(c)
+	}()
+	return c
+}
+
+// vfunc takes a *V and a V
+func vfunc(V, *V) string {
+	return "vfunc"
+}
+
+// valueString takes a string, not a pointer.
+func valueString(v string) string {
+	return "value is ignored"
+}
+
+func add(args ...int) int {
+	sum := 0
+	for _, x := range args {
+		sum += x
+	}
+	return sum
+}
+
+func echo(arg interface{}) interface{} {
+	return arg
+}
+
+func makemap(arg ...string) map[string]string {
+	if len(arg)%2 != 0 {
+		panic("bad makemap")
+	}
+	m := make(map[string]string)
+	for i := 0; i < len(arg); i += 2 {
+		m[arg[i]] = arg[i+1]
+	}
+	return m
+}
+
+func stringer(s fmt.Stringer) string {
+	return s.String()
+}
+
+func mapOfThree() interface{} {
+	return map[string]int{"three": 3}
+}
+
+func testExecute(execTests []execTest, template *Template, t *testing.T) {
+	b := new(bytes.Buffer)
+	funcs := FuncMap{
+		"add":         add,
+		"count":       count,
+		"dddArg":      dddArg,
+		"echo":        echo,
+		"makemap":     makemap,
+		"mapOfThree":  mapOfThree,
+		"oneArg":      oneArg,
+		"stringer":    stringer,
+		"typeOf":      typeOf,
+		"valueString": valueString,
+		"vfunc":       vfunc,
+		"zeroArgs":    zeroArgs,
+	}
+	for _, test := range execTests {
+		var tmpl *Template
+		var err error
+		if template == nil {
+			tmpl, err = New(test.name).Funcs(funcs).Parse(test.input)
+		} else {
+			tmpl, err = template.New(test.name).Funcs(funcs).Parse(test.input)
+		}
+		if err != nil {
+			t.Errorf("%s: parse error: %s", test.name, err)
+			continue
+		}
+		b.Reset()
+		err = tmpl.Execute(b, test.data)
+		switch {
+		case !test.ok && err == nil:
+			t.Errorf("%s: expected error; got none", test.name)
+			continue
+		case test.ok && err != nil:
+			t.Errorf("%s: unexpected execute error: %s", test.name, err)
+			continue
+		case !test.ok && err != nil:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+		}
+		result := b.String()
+		if result != test.output {
+			t.Errorf("%s: expected\n\t%q\ngot\n\t%q", test.name, test.output, result)
+		}
+	}
+}
+
+func TestExecute(t *testing.T) {
+	testExecute(execTests, nil, t)
+}
+
+var delimPairs = []string{
+	"", "", // default
+	"{{", "}}", // same as default
+	"<<", ">>", // distinct
+	"|", "|", // same
+	"(日)", "(本)", // peculiar
+}
+
+func TestDelims(t *testing.T) {
+	const hello = "Hello, world"
+	var value = struct{ Str string }{hello}
+	for i := 0; i < len(delimPairs); i += 2 {
+		text := ".Str"
+		left := delimPairs[i+0]
+		trueLeft := left
+		right := delimPairs[i+1]
+		trueRight := right
+		if left == "" { // default case
+			trueLeft = "{{"
+		}
+		if right == "" { // default case
+			trueRight = "}}"
+		}
+		text = trueLeft + text + trueRight
+		// Now add a comment
+		text += trueLeft + "/*comment*/" + trueRight
+		// Now add  an action containing a string.
+		text += trueLeft + `"` + trueLeft + `"` + trueRight
+		// At this point text looks like `{{.Str}}{{/*comment*/}}{{"{{"}}`.
+		tmpl, err := New("delims").Delims(left, right).Parse(text)
+		if err != nil {
+			t.Fatalf("delim %q text %q parse err %s", left, text, err)
+		}
+		var b = new(bytes.Buffer)
+		err = tmpl.Execute(b, value)
+		if err != nil {
+			t.Fatalf("delim %q exec err %s", left, err)
+		}
+		if b.String() != hello+trueLeft {
+			t.Errorf("expected %q got %q", hello+trueLeft, b.String())
+		}
+	}
+}
+
+// Check that an error from a method flows back to the top.
+func TestExecuteError(t *testing.T) {
+	b := new(bytes.Buffer)
+	tmpl := New("error")
+	_, err := tmpl.Parse("{{.MyError true}}")
+	if err != nil {
+		t.Fatalf("parse error: %s", err)
+	}
+	err = tmpl.Execute(b, tVal)
+	if err == nil {
+		t.Errorf("expected error; got none")
+	} else if !strings.Contains(err.Error(), myError.Error()) {
+		if *debug {
+			fmt.Printf("test execute error: %s\n", err)
+		}
+		t.Errorf("expected myError; got %s", err)
+	}
+}
+
+const execErrorText = `line 1
+line 2
+line 3
+{{template "one" .}}
+{{define "one"}}{{template "two" .}}{{end}}
+{{define "two"}}{{template "three" .}}{{end}}
+{{define "three"}}{{index "hi" $}}{{end}}`
+
+// Check that an error from a nested template contains all the relevant information.
+func TestExecError(t *testing.T) {
+	tmpl, err := New("top").Parse(execErrorText)
+	if err != nil {
+		t.Fatal("parse error:", err)
+	}
+	var b bytes.Buffer
+	err = tmpl.Execute(&b, 5) // 5 is out of range indexing "hi"
+	if err == nil {
+		t.Fatal("expected error")
+	}
+	const want = `template: top:7:20: executing "three" at <index "hi" $>: error calling index: index out of range: 5`
+	got := err.Error()
+	if got != want {
+		t.Errorf("expected\n%q\ngot\n%q", want, got)
+	}
+}
+
+func TestJSEscaping(t *testing.T) {
+	testCases := []struct {
+		in, exp string
+	}{
+		{`a`, `a`},
+		{`'foo`, `\'foo`},
+		{`Go "jump" \`, `Go \"jump\" \\`},
+		{`Yukihiro says "今日は世界"`, `Yukihiro says \"今日は世界\"`},
+		{"unprintable \uFDFF", `unprintable \uFDFF`},
+		{`<html>`, `\x3Chtml\x3E`},
+	}
+	for _, tc := range testCases {
+		s := JSEscapeString(tc.in)
+		if s != tc.exp {
+			t.Errorf("JS escaping [%s] got [%s] want [%s]", tc.in, s, tc.exp)
+		}
+	}
+}
+
+// A nice example: walk a binary tree.
+
+type Tree struct {
+	Val         int
+	Left, Right *Tree
+}
+
+// Use different delimiters to test Set.Delims.
+const treeTemplate = `
+	(define "tree")
+	[
+		(.Val)
+		(with .Left)
+			(template "tree" .)
+		(end)
+		(with .Right)
+			(template "tree" .)
+		(end)
+	]
+	(end)
+`
+
+func TestTree(t *testing.T) {
+	var tree = &Tree{
+		1,
+		&Tree{
+			2, &Tree{
+				3,
+				&Tree{
+					4, nil, nil,
+				},
+				nil,
+			},
+			&Tree{
+				5,
+				&Tree{
+					6, nil, nil,
+				},
+				nil,
+			},
+		},
+		&Tree{
+			7,
+			&Tree{
+				8,
+				&Tree{
+					9, nil, nil,
+				},
+				nil,
+			},
+			&Tree{
+				10,
+				&Tree{
+					11, nil, nil,
+				},
+				nil,
+			},
+		},
+	}
+	tmpl, err := New("root").Delims("(", ")").Parse(treeTemplate)
+	if err != nil {
+		t.Fatal("parse error:", err)
+	}
+	var b bytes.Buffer
+	stripSpace := func(r rune) rune {
+		if r == '\t' || r == '\n' {
+			return -1
+		}
+		return r
+	}
+	const expect = "[1[2[3[4]][5[6]]][7[8[9]][10[11]]]]"
+	// First by looking up the template.
+	err = tmpl.Lookup("tree").Execute(&b, tree)
+	if err != nil {
+		t.Fatal("exec error:", err)
+	}
+	result := strings.Map(stripSpace, b.String())
+	if result != expect {
+		t.Errorf("expected %q got %q", expect, result)
+	}
+	// Then direct to execution.
+	b.Reset()
+	err = tmpl.ExecuteTemplate(&b, "tree", tree)
+	if err != nil {
+		t.Fatal("exec error:", err)
+	}
+	result = strings.Map(stripSpace, b.String())
+	if result != expect {
+		t.Errorf("expected %q got %q", expect, result)
+	}
+}
+
+func TestExecuteOnNewTemplate(t *testing.T) {
+	// This is issue 3872.
+	_ = New("Name").Templates()
+}
+
+const testTemplates = `{{define "one"}}one{{end}}{{define "two"}}two{{end}}`
+
+func TestMessageForExecuteEmpty(t *testing.T) {
+	// Test a truly empty template.
+	tmpl := New("empty")
+	var b bytes.Buffer
+	err := tmpl.Execute(&b, 0)
+	if err == nil {
+		t.Fatal("expected initial error")
+	}
+	got := err.Error()
+	want := `template: empty: "empty" is an incomplete or empty template`
+	if got != want {
+		t.Errorf("expected error %s got %s", want, got)
+	}
+	// Add a non-empty template to check that the error is helpful.
+	tests, err := New("").Parse(testTemplates)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tmpl.AddParseTree("secondary", tests.Tree)
+	err = tmpl.Execute(&b, 0)
+	if err == nil {
+		t.Fatal("expected second error")
+	}
+	got = err.Error()
+	want = `template: empty: "empty" is an incomplete or empty template; defined templates are: "secondary"`
+	if got != want {
+		t.Errorf("expected error %s got %s", want, got)
+	}
+	// Make sure we can execute the secondary.
+	err = tmpl.ExecuteTemplate(&b, "secondary", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+type cmpTest struct {
+	expr  string
+	truth string
+	ok    bool
+}
+
+var cmpTests = []cmpTest{
+	{"eq true true", "true", true},
+	{"eq true false", "false", true},
+	{"eq 1+2i 1+2i", "true", true},
+	{"eq 1+2i 1+3i", "false", true},
+	{"eq 1.5 1.5", "true", true},
+	{"eq 1.5 2.5", "false", true},
+	{"eq 1 1", "true", true},
+	{"eq 1 2", "false", true},
+	{"eq `xy` `xy`", "true", true},
+	{"eq `xy` `xyz`", "false", true},
+	{"eq .Xuint .Xuint", "true", true},
+	{"eq .Xuint .Yuint", "false", true},
+	{"eq 3 4 5 6 3", "true", true},
+	{"eq 3 4 5 6 7", "false", true},
+	{"ne true true", "false", true},
+	{"ne true false", "true", true},
+	{"ne 1+2i 1+2i", "false", true},
+	{"ne 1+2i 1+3i", "true", true},
+	{"ne 1.5 1.5", "false", true},
+	{"ne 1.5 2.5", "true", true},
+	{"ne 1 1", "false", true},
+	{"ne 1 2", "true", true},
+	{"ne `xy` `xy`", "false", true},
+	{"ne `xy` `xyz`", "true", true},
+	{"ne .Xuint .Xuint", "false", true},
+	{"ne .Xuint .Yuint", "true", true},
+	{"lt 1.5 1.5", "false", true},
+	{"lt 1.5 2.5", "true", true},
+	{"lt 1 1", "false", true},
+	{"lt 1 2", "true", true},
+	{"lt `xy` `xy`", "false", true},
+	{"lt `xy` `xyz`", "true", true},
+	{"lt .Xuint .Xuint", "false", true},
+	{"lt .Xuint .Yuint", "true", true},
+	{"le 1.5 1.5", "true", true},
+	{"le 1.5 2.5", "true", true},
+	{"le 2.5 1.5", "false", true},
+	{"le 1 1", "true", true},
+	{"le 1 2", "true", true},
+	{"le 2 1", "false", true},
+	{"le `xy` `xy`", "true", true},
+	{"le `xy` `xyz`", "true", true},
+	{"le `xyz` `xy`", "false", true},
+	{"le .Xuint .Xuint", "true", true},
+	{"le .Xuint .Yuint", "true", true},
+	{"le .Yuint .Xuint", "false", true},
+	{"gt 1.5 1.5", "false", true},
+	{"gt 1.5 2.5", "false", true},
+	{"gt 1 1", "false", true},
+	{"gt 2 1", "true", true},
+	{"gt 1 2", "false", true},
+	{"gt `xy` `xy`", "false", true},
+	{"gt `xy` `xyz`", "false", true},
+	{"gt .Xuint .Xuint", "false", true},
+	{"gt .Xuint .Yuint", "false", true},
+	{"gt .Yuint .Xuint", "true", true},
+	{"ge 1.5 1.5", "true", true},
+	{"ge 1.5 2.5", "false", true},
+	{"ge 2.5 1.5", "true", true},
+	{"ge 1 1", "true", true},
+	{"ge 1 2", "false", true},
+	{"ge 2 1", "true", true},
+	{"ge `xy` `xy`", "true", true},
+	{"ge `xy` `xyz`", "false", true},
+	{"ge `xyz` `xy`", "true", true},
+	{"ge .Xuint .Xuint", "true", true},
+	{"ge .Xuint .Yuint", "false", true},
+	{"ge .Yuint .Xuint", "true", true},
+	// Errors
+	{"eq `xy` 1", "", false},    // Different types.
+	{"lt true true", "", false}, // Unordered types.
+	{"lt 1+0i 1+0i", "", false}, // Unordered types.
+}
+
+func TestComparison(t *testing.T) {
+	b := new(bytes.Buffer)
+	var cmpStruct = struct {
+		Xuint, Yuint uint
+	}{3, 4}
+	for _, test := range cmpTests {
+		text := fmt.Sprintf("{{if %s}}true{{else}}false{{end}}", test.expr)
+		tmpl, err := New("empty").Parse(text)
+		if err != nil {
+			t.Fatal(err)
+		}
+		b.Reset()
+		err = tmpl.Execute(b, &cmpStruct)
+		if test.ok && err != nil {
+			t.Errorf("%s errored incorrectly: %s", test.expr, err)
+			continue
+		}
+		if !test.ok && err == nil {
+			t.Errorf("%s did not error", test.expr)
+			continue
+		}
+		if b.String() != test.truth {
+			t.Errorf("%s: want %s; got %s", test.expr, test.truth, b.String())
+		}
+	}
+}
diff --git a/src/text/template/funcs.go b/src/text/template/funcs.go
new file mode 100644
index 000000000..e85412262
--- /dev/null
+++ b/src/text/template/funcs.go
@@ -0,0 +1,580 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"net/url"
+	"reflect"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// FuncMap is the type of the map defining the mapping from names to functions.
+// Each function must have either a single return value, or two return values of
+// which the second has type error. In that case, if the second (error)
+// return value evaluates to non-nil during execution, execution terminates and
+// Execute returns that error.
+type FuncMap map[string]interface{}
+
+var builtins = FuncMap{
+	"and":      and,
+	"call":     call,
+	"html":     HTMLEscaper,
+	"index":    index,
+	"js":       JSEscaper,
+	"len":      length,
+	"not":      not,
+	"or":       or,
+	"print":    fmt.Sprint,
+	"printf":   fmt.Sprintf,
+	"println":  fmt.Sprintln,
+	"urlquery": URLQueryEscaper,
+
+	// Comparisons
+	"eq": eq, // ==
+	"ge": ge, // >=
+	"gt": gt, // >
+	"le": le, // <=
+	"lt": lt, // <
+	"ne": ne, // !=
+}
+
+var builtinFuncs = createValueFuncs(builtins)
+
+// createValueFuncs turns a FuncMap into a map[string]reflect.Value
+func createValueFuncs(funcMap FuncMap) map[string]reflect.Value {
+	m := make(map[string]reflect.Value)
+	addValueFuncs(m, funcMap)
+	return m
+}
+
+// addValueFuncs adds to values the functions in funcs, converting them to reflect.Values.
+func addValueFuncs(out map[string]reflect.Value, in FuncMap) {
+	for name, fn := range in {
+		v := reflect.ValueOf(fn)
+		if v.Kind() != reflect.Func {
+			panic("value for " + name + " not a function")
+		}
+		if !goodFunc(v.Type()) {
+			panic(fmt.Errorf("can't install method/function %q with %d results", name, v.Type().NumOut()))
+		}
+		out[name] = v
+	}
+}
+
+// addFuncs adds to values the functions in funcs. It does no checking of the input -
+// call addValueFuncs first.
+func addFuncs(out, in FuncMap) {
+	for name, fn := range in {
+		out[name] = fn
+	}
+}
+
+// goodFunc checks that the function or method has the right result signature.
+func goodFunc(typ reflect.Type) bool {
+	// We allow functions with 1 result or 2 results where the second is an error.
+	switch {
+	case typ.NumOut() == 1:
+		return true
+	case typ.NumOut() == 2 && typ.Out(1) == errorType:
+		return true
+	}
+	return false
+}
+
+// findFunction looks for a function in the template, and global map.
+func findFunction(name string, tmpl *Template) (reflect.Value, bool) {
+	if tmpl != nil && tmpl.common != nil {
+		if fn := tmpl.execFuncs[name]; fn.IsValid() {
+			return fn, true
+		}
+	}
+	if fn := builtinFuncs[name]; fn.IsValid() {
+		return fn, true
+	}
+	return reflect.Value{}, false
+}
+
+// Indexing.
+
+// index returns the result of indexing its first argument by the following
+// arguments.  Thus "index x 1 2 3" is, in Go syntax, x[1][2][3]. Each
+// indexed item must be a map, slice, or array.
+func index(item interface{}, indices ...interface{}) (interface{}, error) {
+	v := reflect.ValueOf(item)
+	for _, i := range indices {
+		index := reflect.ValueOf(i)
+		var isNil bool
+		if v, isNil = indirect(v); isNil {
+			return nil, fmt.Errorf("index of nil pointer")
+		}
+		switch v.Kind() {
+		case reflect.Array, reflect.Slice, reflect.String:
+			var x int64
+			switch index.Kind() {
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				x = index.Int()
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+				x = int64(index.Uint())
+			default:
+				return nil, fmt.Errorf("cannot index slice/array with type %s", index.Type())
+			}
+			if x < 0 || x >= int64(v.Len()) {
+				return nil, fmt.Errorf("index out of range: %d", x)
+			}
+			v = v.Index(int(x))
+		case reflect.Map:
+			if !index.IsValid() {
+				index = reflect.Zero(v.Type().Key())
+			}
+			if !index.Type().AssignableTo(v.Type().Key()) {
+				return nil, fmt.Errorf("%s is not index type for %s", index.Type(), v.Type())
+			}
+			if x := v.MapIndex(index); x.IsValid() {
+				v = x
+			} else {
+				v = reflect.Zero(v.Type().Elem())
+			}
+		default:
+			return nil, fmt.Errorf("can't index item of type %s", v.Type())
+		}
+	}
+	return v.Interface(), nil
+}
+
+// Length
+
+// length returns the length of the item, with an error if it has no defined length.
+func length(item interface{}) (int, error) {
+	v, isNil := indirect(reflect.ValueOf(item))
+	if isNil {
+		return 0, fmt.Errorf("len of nil pointer")
+	}
+	switch v.Kind() {
+	case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice, reflect.String:
+		return v.Len(), nil
+	}
+	return 0, fmt.Errorf("len of type %s", v.Type())
+}
+
+// Function invocation
+
+// call returns the result of evaluating the first argument as a function.
+// The function must return 1 result, or 2 results, the second of which is an error.
+func call(fn interface{}, args ...interface{}) (interface{}, error) {
+	v := reflect.ValueOf(fn)
+	typ := v.Type()
+	if typ.Kind() != reflect.Func {
+		return nil, fmt.Errorf("non-function of type %s", typ)
+	}
+	if !goodFunc(typ) {
+		return nil, fmt.Errorf("function called with %d args; should be 1 or 2", typ.NumOut())
+	}
+	numIn := typ.NumIn()
+	var dddType reflect.Type
+	if typ.IsVariadic() {
+		if len(args) < numIn-1 {
+			return nil, fmt.Errorf("wrong number of args: got %d want at least %d", len(args), numIn-1)
+		}
+		dddType = typ.In(numIn - 1).Elem()
+	} else {
+		if len(args) != numIn {
+			return nil, fmt.Errorf("wrong number of args: got %d want %d", len(args), numIn)
+		}
+	}
+	argv := make([]reflect.Value, len(args))
+	for i, arg := range args {
+		value := reflect.ValueOf(arg)
+		// Compute the expected type. Clumsy because of variadics.
+		var argType reflect.Type
+		if !typ.IsVariadic() || i < numIn-1 {
+			argType = typ.In(i)
+		} else {
+			argType = dddType
+		}
+		if !value.IsValid() && canBeNil(argType) {
+			value = reflect.Zero(argType)
+		}
+		if !value.Type().AssignableTo(argType) {
+			return nil, fmt.Errorf("arg %d has type %s; should be %s", i, value.Type(), argType)
+		}
+		argv[i] = value
+	}
+	result := v.Call(argv)
+	if len(result) == 2 && !result[1].IsNil() {
+		return result[0].Interface(), result[1].Interface().(error)
+	}
+	return result[0].Interface(), nil
+}
+
+// Boolean logic.
+
+func truth(a interface{}) bool {
+	t, _ := isTrue(reflect.ValueOf(a))
+	return t
+}
+
+// and computes the Boolean AND of its arguments, returning
+// the first false argument it encounters, or the last argument.
+func and(arg0 interface{}, args ...interface{}) interface{} {
+	if !truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if !truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// or computes the Boolean OR of its arguments, returning
+// the first true argument it encounters, or the last argument.
+func or(arg0 interface{}, args ...interface{}) interface{} {
+	if truth(arg0) {
+		return arg0
+	}
+	for i := range args {
+		arg0 = args[i]
+		if truth(arg0) {
+			break
+		}
+	}
+	return arg0
+}
+
+// not returns the Boolean negation of its argument.
+func not(arg interface{}) (truth bool) {
+	truth, _ = isTrue(reflect.ValueOf(arg))
+	return !truth
+}
+
+// Comparison.
+
+// TODO: Perhaps allow comparison between signed and unsigned integers.
+
+var (
+	errBadComparisonType = errors.New("invalid type for comparison")
+	errBadComparison     = errors.New("incompatible types for comparison")
+	errNoComparison      = errors.New("missing argument for comparison")
+)
+
+type kind int
+
+const (
+	invalidKind kind = iota
+	boolKind
+	complexKind
+	intKind
+	floatKind
+	integerKind
+	stringKind
+	uintKind
+)
+
+func basicKind(v reflect.Value) (kind, error) {
+	switch v.Kind() {
+	case reflect.Bool:
+		return boolKind, nil
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return intKind, nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return uintKind, nil
+	case reflect.Float32, reflect.Float64:
+		return floatKind, nil
+	case reflect.Complex64, reflect.Complex128:
+		return complexKind, nil
+	case reflect.String:
+		return stringKind, nil
+	}
+	return invalidKind, errBadComparisonType
+}
+
+// eq evaluates the comparison a == b || a == c || ...
+func eq(arg1 interface{}, arg2 ...interface{}) (bool, error) {
+	v1 := reflect.ValueOf(arg1)
+	k1, err := basicKind(v1)
+	if err != nil {
+		return false, err
+	}
+	if len(arg2) == 0 {
+		return false, errNoComparison
+	}
+	for _, arg := range arg2 {
+		v2 := reflect.ValueOf(arg)
+		k2, err := basicKind(v2)
+		if err != nil {
+			return false, err
+		}
+		if k1 != k2 {
+			return false, errBadComparison
+		}
+		truth := false
+		switch k1 {
+		case boolKind:
+			truth = v1.Bool() == v2.Bool()
+		case complexKind:
+			truth = v1.Complex() == v2.Complex()
+		case floatKind:
+			truth = v1.Float() == v2.Float()
+		case intKind:
+			truth = v1.Int() == v2.Int()
+		case stringKind:
+			truth = v1.String() == v2.String()
+		case uintKind:
+			truth = v1.Uint() == v2.Uint()
+		default:
+			panic("invalid kind")
+		}
+		if truth {
+			return true, nil
+		}
+	}
+	return false, nil
+}
+
+// ne evaluates the comparison a != b.
+func ne(arg1, arg2 interface{}) (bool, error) {
+	// != is the inverse of ==.
+	equal, err := eq(arg1, arg2)
+	return !equal, err
+}
+
+// lt evaluates the comparison a < b.
+func lt(arg1, arg2 interface{}) (bool, error) {
+	v1 := reflect.ValueOf(arg1)
+	k1, err := basicKind(v1)
+	if err != nil {
+		return false, err
+	}
+	v2 := reflect.ValueOf(arg2)
+	k2, err := basicKind(v2)
+	if err != nil {
+		return false, err
+	}
+	if k1 != k2 {
+		return false, errBadComparison
+	}
+	truth := false
+	switch k1 {
+	case boolKind, complexKind:
+		return false, errBadComparisonType
+	case floatKind:
+		truth = v1.Float() < v2.Float()
+	case intKind:
+		truth = v1.Int() < v2.Int()
+	case stringKind:
+		truth = v1.String() < v2.String()
+	case uintKind:
+		truth = v1.Uint() < v2.Uint()
+	default:
+		panic("invalid kind")
+	}
+	return truth, nil
+}
+
+// le evaluates the comparison <= b.
+func le(arg1, arg2 interface{}) (bool, error) {
+	// <= is < or ==.
+	lessThan, err := lt(arg1, arg2)
+	if lessThan || err != nil {
+		return lessThan, err
+	}
+	return eq(arg1, arg2)
+}
+
+// gt evaluates the comparison a > b.
+func gt(arg1, arg2 interface{}) (bool, error) {
+	// > is the inverse of <=.
+	lessOrEqual, err := le(arg1, arg2)
+	if err != nil {
+		return false, err
+	}
+	return !lessOrEqual, nil
+}
+
+// ge evaluates the comparison a >= b.
+func ge(arg1, arg2 interface{}) (bool, error) {
+	// >= is the inverse of <.
+	lessThan, err := lt(arg1, arg2)
+	if err != nil {
+		return false, err
+	}
+	return !lessThan, nil
+}
+
+// HTML escaping.
+
+var (
+	htmlQuot = []byte("&#34;") // shorter than "&quot;"
+	htmlApos = []byte("&#39;") // shorter than "&apos;" and apos was not in HTML until HTML5
+	htmlAmp  = []byte("&amp;")
+	htmlLt   = []byte("&lt;")
+	htmlGt   = []byte("&gt;")
+)
+
+// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
+func HTMLEscape(w io.Writer, b []byte) {
+	last := 0
+	for i, c := range b {
+		var html []byte
+		switch c {
+		case '"':
+			html = htmlQuot
+		case '\'':
+			html = htmlApos
+		case '&':
+			html = htmlAmp
+		case '<':
+			html = htmlLt
+		case '>':
+			html = htmlGt
+		default:
+			continue
+		}
+		w.Write(b[last:i])
+		w.Write(html)
+		last = i + 1
+	}
+	w.Write(b[last:])
+}
+
+// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
+func HTMLEscapeString(s string) string {
+	// Avoid allocation if we can.
+	if strings.IndexAny(s, `'"&<>`) < 0 {
+		return s
+	}
+	var b bytes.Buffer
+	HTMLEscape(&b, []byte(s))
+	return b.String()
+}
+
+// HTMLEscaper returns the escaped HTML equivalent of the textual
+// representation of its arguments.
+func HTMLEscaper(args ...interface{}) string {
+	return HTMLEscapeString(evalArgs(args))
+}
+
+// JavaScript escaping.
+
+var (
+	jsLowUni = []byte(`\u00`)
+	hex      = []byte("0123456789ABCDEF")
+
+	jsBackslash = []byte(`\\`)
+	jsApos      = []byte(`\'`)
+	jsQuot      = []byte(`\"`)
+	jsLt        = []byte(`\x3C`)
+	jsGt        = []byte(`\x3E`)
+)
+
+// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
+func JSEscape(w io.Writer, b []byte) {
+	last := 0
+	for i := 0; i < len(b); i++ {
+		c := b[i]
+
+		if !jsIsSpecial(rune(c)) {
+			// fast path: nothing to do
+			continue
+		}
+		w.Write(b[last:i])
+
+		if c < utf8.RuneSelf {
+			// Quotes, slashes and angle brackets get quoted.
+			// Control characters get written as \u00XX.
+			switch c {
+			case '\\':
+				w.Write(jsBackslash)
+			case '\'':
+				w.Write(jsApos)
+			case '"':
+				w.Write(jsQuot)
+			case '<':
+				w.Write(jsLt)
+			case '>':
+				w.Write(jsGt)
+			default:
+				w.Write(jsLowUni)
+				t, b := c>>4, c&0x0f
+				w.Write(hex[t : t+1])
+				w.Write(hex[b : b+1])
+			}
+		} else {
+			// Unicode rune.
+			r, size := utf8.DecodeRune(b[i:])
+			if unicode.IsPrint(r) {
+				w.Write(b[i : i+size])
+			} else {
+				fmt.Fprintf(w, "\\u%04X", r)
+			}
+			i += size - 1
+		}
+		last = i + 1
+	}
+	w.Write(b[last:])
+}
+
+// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
+func JSEscapeString(s string) string {
+	// Avoid allocation if we can.
+	if strings.IndexFunc(s, jsIsSpecial) < 0 {
+		return s
+	}
+	var b bytes.Buffer
+	JSEscape(&b, []byte(s))
+	return b.String()
+}
+
+func jsIsSpecial(r rune) bool {
+	switch r {
+	case '\\', '\'', '"', '<', '>':
+		return true
+	}
+	return r < ' ' || utf8.RuneSelf <= r
+}
+
+// JSEscaper returns the escaped JavaScript equivalent of the textual
+// representation of its arguments.
+func JSEscaper(args ...interface{}) string {
+	return JSEscapeString(evalArgs(args))
+}
+
+// URLQueryEscaper returns the escaped value of the textual representation of
+// its arguments in a form suitable for embedding in a URL query.
+func URLQueryEscaper(args ...interface{}) string {
+	return url.QueryEscape(evalArgs(args))
+}
+
+// evalArgs formats the list of arguments into a string. It is therefore equivalent to
+//	fmt.Sprint(args...)
+// except that each argument is indirected (if a pointer), as required,
+// using the same rules as the default string evaluation during template
+// execution.
+func evalArgs(args []interface{}) string {
+	ok := false
+	var s string
+	// Fast path for simple common case.
+	if len(args) == 1 {
+		s, ok = args[0].(string)
+	}
+	if !ok {
+		for i, arg := range args {
+			a, ok := printableValue(reflect.ValueOf(arg))
+			if ok {
+				args[i] = a
+			} // else left fmt do its thing
+		}
+		s = fmt.Sprint(args...)
+	}
+	return s
+}
diff --git a/src/text/template/helper.go b/src/text/template/helper.go
new file mode 100644
index 000000000..3636fb54d
--- /dev/null
+++ b/src/text/template/helper.go
@@ -0,0 +1,108 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Helper functions to make constructing templates easier.
+
+package template
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+)
+
+// Functions and methods to parse templates.
+
+// Must is a helper that wraps a call to a function returning (*Template, error)
+// and panics if the error is non-nil. It is intended for use in variable
+// initializations such as
+//	var t = template.Must(template.New("name").Parse("text"))
+func Must(t *Template, err error) *Template {
+	if err != nil {
+		panic(err)
+	}
+	return t
+}
+
+// ParseFiles creates a new Template and parses the template definitions from
+// the named files. The returned template's name will have the (base) name and
+// (parsed) contents of the first file. There must be at least one file.
+// If an error occurs, parsing stops and the returned *Template is nil.
+func ParseFiles(filenames ...string) (*Template, error) {
+	return parseFiles(nil, filenames...)
+}
+
+// ParseFiles parses the named files and associates the resulting templates with
+// t. If an error occurs, parsing stops and the returned template is nil;
+// otherwise it is t. There must be at least one file.
+func (t *Template) ParseFiles(filenames ...string) (*Template, error) {
+	return parseFiles(t, filenames...)
+}
+
+// parseFiles is the helper for the method and function. If the argument
+// template is nil, it is created from the first file.
+func parseFiles(t *Template, filenames ...string) (*Template, error) {
+	if len(filenames) == 0 {
+		// Not really a problem, but be consistent.
+		return nil, fmt.Errorf("template: no files named in call to ParseFiles")
+	}
+	for _, filename := range filenames {
+		b, err := ioutil.ReadFile(filename)
+		if err != nil {
+			return nil, err
+		}
+		s := string(b)
+		name := filepath.Base(filename)
+		// First template becomes return value if not already defined,
+		// and we use that one for subsequent New calls to associate
+		// all the templates together. Also, if this file has the same name
+		// as t, this file becomes the contents of t, so
+		//  t, err := New(name).Funcs(xxx).ParseFiles(name)
+		// works. Otherwise we create a new template associated with t.
+		var tmpl *Template
+		if t == nil {
+			t = New(name)
+		}
+		if name == t.Name() {
+			tmpl = t
+		} else {
+			tmpl = t.New(name)
+		}
+		_, err = tmpl.Parse(s)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return t, nil
+}
+
+// ParseGlob creates a new Template and parses the template definitions from the
+// files identified by the pattern, which must match at least one file. The
+// returned template will have the (base) name and (parsed) contents of the
+// first file matched by the pattern. ParseGlob is equivalent to calling
+// ParseFiles with the list of files matched by the pattern.
+func ParseGlob(pattern string) (*Template, error) {
+	return parseGlob(nil, pattern)
+}
+
+// ParseGlob parses the template definitions in the files identified by the
+// pattern and associates the resulting templates with t. The pattern is
+// processed by filepath.Glob and must match at least one file. ParseGlob is
+// equivalent to calling t.ParseFiles with the list of files matched by the
+// pattern.
+func (t *Template) ParseGlob(pattern string) (*Template, error) {
+	return parseGlob(t, pattern)
+}
+
+// parseGlob is the implementation of the function and method ParseGlob.
+func parseGlob(t *Template, pattern string) (*Template, error) {
+	filenames, err := filepath.Glob(pattern)
+	if err != nil {
+		return nil, err
+	}
+	if len(filenames) == 0 {
+		return nil, fmt.Errorf("template: pattern matches no files: %#q", pattern)
+	}
+	return parseFiles(t, filenames...)
+}
diff --git a/src/text/template/multi_test.go b/src/text/template/multi_test.go
new file mode 100644
index 000000000..e4e804880
--- /dev/null
+++ b/src/text/template/multi_test.go
@@ -0,0 +1,292 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+// Tests for mulitple-template parsing and execution.
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"testing"
+	"text/template/parse"
+)
+
+const (
+	noError  = true
+	hasError = false
+)
+
+type multiParseTest struct {
+	name    string
+	input   string
+	ok      bool
+	names   []string
+	results []string
+}
+
+var multiParseTests = []multiParseTest{
+	{"empty", "", noError,
+		nil,
+		nil},
+	{"one", `{{define "foo"}} FOO {{end}}`, noError,
+		[]string{"foo"},
+		[]string{" FOO "}},
+	{"two", `{{define "foo"}} FOO {{end}}{{define "bar"}} BAR {{end}}`, noError,
+		[]string{"foo", "bar"},
+		[]string{" FOO ", " BAR "}},
+	// errors
+	{"missing end", `{{define "foo"}} FOO `, hasError,
+		nil,
+		nil},
+	{"malformed name", `{{define "foo}} FOO `, hasError,
+		nil,
+		nil},
+}
+
+func TestMultiParse(t *testing.T) {
+	for _, test := range multiParseTests {
+		template, err := New("root").Parse(test.input)
+		switch {
+		case err == nil && !test.ok:
+			t.Errorf("%q: expected error; got none", test.name)
+			continue
+		case err != nil && test.ok:
+			t.Errorf("%q: unexpected error: %v", test.name, err)
+			continue
+		case err != nil && !test.ok:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+			continue
+		}
+		if template == nil {
+			continue
+		}
+		if len(template.tmpl) != len(test.names)+1 { // +1 for root
+			t.Errorf("%s: wrong number of templates; wanted %d got %d", test.name, len(test.names), len(template.tmpl))
+			continue
+		}
+		for i, name := range test.names {
+			tmpl, ok := template.tmpl[name]
+			if !ok {
+				t.Errorf("%s: can't find template %q", test.name, name)
+				continue
+			}
+			result := tmpl.Root.String()
+			if result != test.results[i] {
+				t.Errorf("%s=(%q): got\n\t%v\nexpected\n\t%v", test.name, test.input, result, test.results[i])
+			}
+		}
+	}
+}
+
+var multiExecTests = []execTest{
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+	{"invoke x", `{{template "x" .SI}}`, "TEXT", tVal, true},
+	{"invoke x no args", `{{template "x"}}`, "TEXT", tVal, true},
+	{"invoke dot int", `{{template "dot" .I}}`, "17", tVal, true},
+	{"invoke dot []int", `{{template "dot" .SI}}`, "[3 4 5]", tVal, true},
+	{"invoke dotV", `{{template "dotV" .U}}`, "v", tVal, true},
+	{"invoke nested int", `{{template "nested" .I}}`, "17", tVal, true},
+	{"variable declared by template", `{{template "nested" $x:=.SI}},{{index $x 1}}`, "[3 4 5],4", tVal, true},
+
+	// User-defined function: test argument evaluator.
+	{"testFunc literal", `{{oneArg "joe"}}`, "oneArg=joe", tVal, true},
+	{"testFunc .", `{{oneArg .}}`, "oneArg=joe", "joe", true},
+}
+
+// These strings are also in testdata/*.
+const multiText1 = `
+	{{define "x"}}TEXT{{end}}
+	{{define "dotV"}}{{.V}}{{end}}
+`
+
+const multiText2 = `
+	{{define "dot"}}{{.}}{{end}}
+	{{define "nested"}}{{template "dot" .}}{{end}}
+`
+
+func TestMultiExecute(t *testing.T) {
+	// Declare a couple of templates first.
+	template, err := New("root").Parse(multiText1)
+	if err != nil {
+		t.Fatalf("parse error for 1: %s", err)
+	}
+	_, err = template.Parse(multiText2)
+	if err != nil {
+		t.Fatalf("parse error for 2: %s", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseFiles(t *testing.T) {
+	_, err := ParseFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	template := New("root")
+	_, err = template.ParseFiles("testdata/file1.tmpl", "testdata/file2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseGlob(t *testing.T) {
+	_, err := ParseGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = New("error").ParseGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	template := New("root")
+	_, err = template.ParseGlob("testdata/file*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+// In these tests, actual content (not just template definitions) comes from the parsed files.
+
+var templateFileExecTests = []execTest{
+	{"test", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\n\ny\ntemplate2\n\nx\n", 0, true},
+}
+
+func TestParseFilesWithData(t *testing.T) {
+	template, err := New("root").ParseFiles("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+func TestParseGlobWithData(t *testing.T) {
+	template, err := New("root").ParseGlob("testdata/tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+const (
+	cloneText1 = `{{define "a"}}{{template "b"}}{{template "c"}}{{end}}`
+	cloneText2 = `{{define "b"}}b{{end}}`
+	cloneText3 = `{{define "c"}}root{{end}}`
+	cloneText4 = `{{define "c"}}clone{{end}}`
+)
+
+func TestClone(t *testing.T) {
+	// Create some templates and clone the root.
+	root, err := New("root").Parse(cloneText1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = root.Parse(cloneText2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	clone := Must(root.Clone())
+	// Add variants to both.
+	_, err = root.Parse(cloneText3)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = clone.Parse(cloneText4)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Verify that the clone is self-consistent.
+	for k, v := range clone.tmpl {
+		if k == clone.name && v.tmpl[k] != clone {
+			t.Error("clone does not contain root")
+		}
+		if v != v.tmpl[v.name] {
+			t.Errorf("clone does not contain self for %q", k)
+		}
+	}
+	// Execute root.
+	var b bytes.Buffer
+	err = root.ExecuteTemplate(&b, "a", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "broot" {
+		t.Errorf("expected %q got %q", "broot", b.String())
+	}
+	// Execute copy.
+	b.Reset()
+	err = clone.ExecuteTemplate(&b, "a", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "bclone" {
+		t.Errorf("expected %q got %q", "bclone", b.String())
+	}
+}
+
+func TestAddParseTree(t *testing.T) {
+	// Create some templates.
+	root, err := New("root").Parse(cloneText1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = root.Parse(cloneText2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// Add a new parse tree.
+	tree, err := parse.Parse("cloneText3", cloneText3, "", "", nil, builtins)
+	if err != nil {
+		t.Fatal(err)
+	}
+	added, err := root.AddParseTree("c", tree["c"])
+	// Execute.
+	var b bytes.Buffer
+	err = added.ExecuteTemplate(&b, "a", 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "broot" {
+		t.Errorf("expected %q got %q", "broot", b.String())
+	}
+}
+
+// Issue 7032
+func TestAddParseTreeToUnparsedTemplate(t *testing.T) {
+	master := "{{define \"master\"}}{{end}}"
+	tmpl := New("master")
+	tree, err := parse.Parse("master", master, "", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected parse err: %v", err)
+	}
+	masterTree := tree["master"]
+	tmpl.AddParseTree("master", masterTree) // used to panic
+}
+
+func TestRedefinition(t *testing.T) {
+	var tmpl *Template
+	var err error
+	if tmpl, err = New("tmpl1").Parse(`{{define "test"}}foo{{end}}`); err != nil {
+		t.Fatalf("parse 1: %v", err)
+	}
+	if _, err = tmpl.Parse(`{{define "test"}}bar{{end}}`); err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "redefinition") {
+		t.Fatalf("expected redefinition error; got %v", err)
+	}
+	if _, err = tmpl.New("tmpl2").Parse(`{{define "test"}}bar{{end}}`); err == nil {
+		t.Fatal("expected error")
+	}
+	if !strings.Contains(err.Error(), "redefinition") {
+		t.Fatalf("expected redefinition error; got %v", err)
+	}
+}
diff --git a/src/text/template/parse/lex.go b/src/text/template/parse/lex.go
new file mode 100644
index 000000000..1674aaf9c
--- /dev/null
+++ b/src/text/template/parse/lex.go
@@ -0,0 +1,551 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"fmt"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+// item represents a token or text string returned from the scanner.
+type item struct {
+	typ itemType // The type of this item.
+	pos Pos      // The starting position, in bytes, of this item in the input string.
+	val string   // The value of this item.
+}
+
+func (i item) String() string {
+	switch {
+	case i.typ == itemEOF:
+		return "EOF"
+	case i.typ == itemError:
+		return i.val
+	case i.typ > itemKeyword:
+		return fmt.Sprintf("<%s>", i.val)
+	case len(i.val) > 10:
+		return fmt.Sprintf("%.10q...", i.val)
+	}
+	return fmt.Sprintf("%q", i.val)
+}
+
+// itemType identifies the type of lex items.
+type itemType int
+
+const (
+	itemError        itemType = iota // error occurred; value is text of error
+	itemBool                         // boolean constant
+	itemChar                         // printable ASCII character; grab bag for comma etc.
+	itemCharConstant                 // character constant
+	itemComplex                      // complex constant (1+2i); imaginary is just a number
+	itemColonEquals                  // colon-equals (':=') introducing a declaration
+	itemEOF
+	itemField      // alphanumeric identifier starting with '.'
+	itemIdentifier // alphanumeric identifier not starting with '.'
+	itemLeftDelim  // left action delimiter
+	itemLeftParen  // '(' inside action
+	itemNumber     // simple number, including imaginary
+	itemPipe       // pipe symbol
+	itemRawString  // raw quoted string (includes quotes)
+	itemRightDelim // right action delimiter
+	itemRightParen // ')' inside action
+	itemSpace      // run of spaces separating arguments
+	itemString     // quoted string (includes quotes)
+	itemText       // plain text
+	itemVariable   // variable starting with '$', such as '$' or  '$1' or '$hello'
+	// Keywords appear after all the rest.
+	itemKeyword  // used only to delimit the keywords
+	itemDot      // the cursor, spelled '.'
+	itemDefine   // define keyword
+	itemElse     // else keyword
+	itemEnd      // end keyword
+	itemIf       // if keyword
+	itemNil      // the untyped nil constant, easiest to treat as a keyword
+	itemRange    // range keyword
+	itemTemplate // template keyword
+	itemWith     // with keyword
+)
+
+var key = map[string]itemType{
+	".":        itemDot,
+	"define":   itemDefine,
+	"else":     itemElse,
+	"end":      itemEnd,
+	"if":       itemIf,
+	"range":    itemRange,
+	"nil":      itemNil,
+	"template": itemTemplate,
+	"with":     itemWith,
+}
+
+const eof = -1
+
+// stateFn represents the state of the scanner as a function that returns the next state.
+type stateFn func(*lexer) stateFn
+
+// lexer holds the state of the scanner.
+type lexer struct {
+	name       string    // the name of the input; used only for error reports
+	input      string    // the string being scanned
+	leftDelim  string    // start of action
+	rightDelim string    // end of action
+	state      stateFn   // the next lexing function to enter
+	pos        Pos       // current position in the input
+	start      Pos       // start position of this item
+	width      Pos       // width of last rune read from input
+	lastPos    Pos       // position of most recent item returned by nextItem
+	items      chan item // channel of scanned items
+	parenDepth int       // nesting depth of ( ) exprs
+}
+
+// next returns the next rune in the input.
+func (l *lexer) next() rune {
+	if int(l.pos) >= len(l.input) {
+		l.width = 0
+		return eof
+	}
+	r, w := utf8.DecodeRuneInString(l.input[l.pos:])
+	l.width = Pos(w)
+	l.pos += l.width
+	return r
+}
+
+// peek returns but does not consume the next rune in the input.
+func (l *lexer) peek() rune {
+	r := l.next()
+	l.backup()
+	return r
+}
+
+// backup steps back one rune. Can only be called once per call of next.
+func (l *lexer) backup() {
+	l.pos -= l.width
+}
+
+// emit passes an item back to the client.
+func (l *lexer) emit(t itemType) {
+	l.items <- item{t, l.start, l.input[l.start:l.pos]}
+	l.start = l.pos
+}
+
+// ignore skips over the pending input before this point.
+func (l *lexer) ignore() {
+	l.start = l.pos
+}
+
+// accept consumes the next rune if it's from the valid set.
+func (l *lexer) accept(valid string) bool {
+	if strings.IndexRune(valid, l.next()) >= 0 {
+		return true
+	}
+	l.backup()
+	return false
+}
+
+// acceptRun consumes a run of runes from the valid set.
+func (l *lexer) acceptRun(valid string) {
+	for strings.IndexRune(valid, l.next()) >= 0 {
+	}
+	l.backup()
+}
+
+// lineNumber reports which line we're on, based on the position of
+// the previous item returned by nextItem. Doing it this way
+// means we don't have to worry about peek double counting.
+func (l *lexer) lineNumber() int {
+	return 1 + strings.Count(l.input[:l.lastPos], "\n")
+}
+
+// errorf returns an error token and terminates the scan by passing
+// back a nil pointer that will be the next state, terminating l.nextItem.
+func (l *lexer) errorf(format string, args ...interface{}) stateFn {
+	l.items <- item{itemError, l.start, fmt.Sprintf(format, args...)}
+	return nil
+}
+
+// nextItem returns the next item from the input.
+func (l *lexer) nextItem() item {
+	item := <-l.items
+	l.lastPos = item.pos
+	return item
+}
+
+// lex creates a new scanner for the input string.
+func lex(name, input, left, right string) *lexer {
+	if left == "" {
+		left = leftDelim
+	}
+	if right == "" {
+		right = rightDelim
+	}
+	l := &lexer{
+		name:       name,
+		input:      input,
+		leftDelim:  left,
+		rightDelim: right,
+		items:      make(chan item),
+	}
+	go l.run()
+	return l
+}
+
+// run runs the state machine for the lexer.
+func (l *lexer) run() {
+	for l.state = lexText; l.state != nil; {
+		l.state = l.state(l)
+	}
+}
+
+// state functions
+
+const (
+	leftDelim    = "{{"
+	rightDelim   = "}}"
+	leftComment  = "/*"
+	rightComment = "*/"
+)
+
+// lexText scans until an opening action delimiter, "{{".
+func lexText(l *lexer) stateFn {
+	for {
+		if strings.HasPrefix(l.input[l.pos:], l.leftDelim) {
+			if l.pos > l.start {
+				l.emit(itemText)
+			}
+			return lexLeftDelim
+		}
+		if l.next() == eof {
+			break
+		}
+	}
+	// Correctly reached EOF.
+	if l.pos > l.start {
+		l.emit(itemText)
+	}
+	l.emit(itemEOF)
+	return nil
+}
+
+// lexLeftDelim scans the left delimiter, which is known to be present.
+func lexLeftDelim(l *lexer) stateFn {
+	l.pos += Pos(len(l.leftDelim))
+	if strings.HasPrefix(l.input[l.pos:], leftComment) {
+		return lexComment
+	}
+	l.emit(itemLeftDelim)
+	l.parenDepth = 0
+	return lexInsideAction
+}
+
+// lexComment scans a comment. The left comment marker is known to be present.
+func lexComment(l *lexer) stateFn {
+	l.pos += Pos(len(leftComment))
+	i := strings.Index(l.input[l.pos:], rightComment)
+	if i < 0 {
+		return l.errorf("unclosed comment")
+	}
+	l.pos += Pos(i + len(rightComment))
+	if !strings.HasPrefix(l.input[l.pos:], l.rightDelim) {
+		return l.errorf("comment ends before closing delimiter")
+
+	}
+	l.pos += Pos(len(l.rightDelim))
+	l.ignore()
+	return lexText
+}
+
+// lexRightDelim scans the right delimiter, which is known to be present.
+func lexRightDelim(l *lexer) stateFn {
+	l.pos += Pos(len(l.rightDelim))
+	l.emit(itemRightDelim)
+	return lexText
+}
+
+// lexInsideAction scans the elements inside action delimiters.
+func lexInsideAction(l *lexer) stateFn {
+	// Either number, quoted string, or identifier.
+	// Spaces separate arguments; runs of spaces turn into itemSpace.
+	// Pipe symbols separate and are emitted.
+	if strings.HasPrefix(l.input[l.pos:], l.rightDelim) {
+		if l.parenDepth == 0 {
+			return lexRightDelim
+		}
+		return l.errorf("unclosed left paren")
+	}
+	switch r := l.next(); {
+	case r == eof || isEndOfLine(r):
+		return l.errorf("unclosed action")
+	case isSpace(r):
+		return lexSpace
+	case r == ':':
+		if l.next() != '=' {
+			return l.errorf("expected :=")
+		}
+		l.emit(itemColonEquals)
+	case r == '|':
+		l.emit(itemPipe)
+	case r == '"':
+		return lexQuote
+	case r == '`':
+		return lexRawQuote
+	case r == '$':
+		return lexVariable
+	case r == '\'':
+		return lexChar
+	case r == '.':
+		// special look-ahead for ".field" so we don't break l.backup().
+		if l.pos < Pos(len(l.input)) {
+			r := l.input[l.pos]
+			if r < '0' || '9' < r {
+				return lexField
+			}
+		}
+		fallthrough // '.' can start a number.
+	case r == '+' || r == '-' || ('0' <= r && r <= '9'):
+		l.backup()
+		return lexNumber
+	case isAlphaNumeric(r):
+		l.backup()
+		return lexIdentifier
+	case r == '(':
+		l.emit(itemLeftParen)
+		l.parenDepth++
+		return lexInsideAction
+	case r == ')':
+		l.emit(itemRightParen)
+		l.parenDepth--
+		if l.parenDepth < 0 {
+			return l.errorf("unexpected right paren %#U", r)
+		}
+		return lexInsideAction
+	case r <= unicode.MaxASCII && unicode.IsPrint(r):
+		l.emit(itemChar)
+		return lexInsideAction
+	default:
+		return l.errorf("unrecognized character in action: %#U", r)
+	}
+	return lexInsideAction
+}
+
+// lexSpace scans a run of space characters.
+// One space has already been seen.
+func lexSpace(l *lexer) stateFn {
+	for isSpace(l.peek()) {
+		l.next()
+	}
+	l.emit(itemSpace)
+	return lexInsideAction
+}
+
+// lexIdentifier scans an alphanumeric.
+func lexIdentifier(l *lexer) stateFn {
+Loop:
+	for {
+		switch r := l.next(); {
+		case isAlphaNumeric(r):
+			// absorb.
+		default:
+			l.backup()
+			word := l.input[l.start:l.pos]
+			if !l.atTerminator() {
+				return l.errorf("bad character %#U", r)
+			}
+			switch {
+			case key[word] > itemKeyword:
+				l.emit(key[word])
+			case word[0] == '.':
+				l.emit(itemField)
+			case word == "true", word == "false":
+				l.emit(itemBool)
+			default:
+				l.emit(itemIdentifier)
+			}
+			break Loop
+		}
+	}
+	return lexInsideAction
+}
+
+// lexField scans a field: .Alphanumeric.
+// The . has been scanned.
+func lexField(l *lexer) stateFn {
+	return lexFieldOrVariable(l, itemField)
+}
+
+// lexVariable scans a Variable: $Alphanumeric.
+// The $ has been scanned.
+func lexVariable(l *lexer) stateFn {
+	if l.atTerminator() { // Nothing interesting follows -> "$".
+		l.emit(itemVariable)
+		return lexInsideAction
+	}
+	return lexFieldOrVariable(l, itemVariable)
+}
+
+// lexVariable scans a field or variable: [.$]Alphanumeric.
+// The . or $ has been scanned.
+func lexFieldOrVariable(l *lexer, typ itemType) stateFn {
+	if l.atTerminator() { // Nothing interesting follows -> "." or "$".
+		if typ == itemVariable {
+			l.emit(itemVariable)
+		} else {
+			l.emit(itemDot)
+		}
+		return lexInsideAction
+	}
+	var r rune
+	for {
+		r = l.next()
+		if !isAlphaNumeric(r) {
+			l.backup()
+			break
+		}
+	}
+	if !l.atTerminator() {
+		return l.errorf("bad character %#U", r)
+	}
+	l.emit(typ)
+	return lexInsideAction
+}
+
+// atTerminator reports whether the input is at valid termination character to
+// appear after an identifier. Breaks .X.Y into two pieces. Also catches cases
+// like "$x+2" not being acceptable without a space, in case we decide one
+// day to implement arithmetic.
+func (l *lexer) atTerminator() bool {
+	r := l.peek()
+	if isSpace(r) || isEndOfLine(r) {
+		return true
+	}
+	switch r {
+	case eof, '.', ',', '|', ':', ')', '(':
+		return true
+	}
+	// Does r start the delimiter? This can be ambiguous (with delim=="//", $x/2 will
+	// succeed but should fail) but only in extremely rare cases caused by willfully
+	// bad choice of delimiter.
+	if rd, _ := utf8.DecodeRuneInString(l.rightDelim); rd == r {
+		return true
+	}
+	return false
+}
+
+// lexChar scans a character constant. The initial quote is already
+// scanned. Syntax checking is done by the parser.
+func lexChar(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != eof && r != '\n' {
+				break
+			}
+			fallthrough
+		case eof, '\n':
+			return l.errorf("unterminated character constant")
+		case '\'':
+			break Loop
+		}
+	}
+	l.emit(itemCharConstant)
+	return lexInsideAction
+}
+
+// lexNumber scans a number: decimal, octal, hex, float, or imaginary. This
+// isn't a perfect number scanner - for instance it accepts "." and "0x0.2"
+// and "089" - but when it's wrong the input is invalid and the parser (via
+// strconv) will notice.
+func lexNumber(l *lexer) stateFn {
+	if !l.scanNumber() {
+		return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
+	}
+	if sign := l.peek(); sign == '+' || sign == '-' {
+		// Complex: 1+2i. No spaces, must end in 'i'.
+		if !l.scanNumber() || l.input[l.pos-1] != 'i' {
+			return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
+		}
+		l.emit(itemComplex)
+	} else {
+		l.emit(itemNumber)
+	}
+	return lexInsideAction
+}
+
+func (l *lexer) scanNumber() bool {
+	// Optional leading sign.
+	l.accept("+-")
+	// Is it hex?
+	digits := "0123456789"
+	if l.accept("0") && l.accept("xX") {
+		digits = "0123456789abcdefABCDEF"
+	}
+	l.acceptRun(digits)
+	if l.accept(".") {
+		l.acceptRun(digits)
+	}
+	if l.accept("eE") {
+		l.accept("+-")
+		l.acceptRun("0123456789")
+	}
+	// Is it imaginary?
+	l.accept("i")
+	// Next thing mustn't be alphanumeric.
+	if isAlphaNumeric(l.peek()) {
+		l.next()
+		return false
+	}
+	return true
+}
+
+// lexQuote scans a quoted string.
+func lexQuote(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case '\\':
+			if r := l.next(); r != eof && r != '\n' {
+				break
+			}
+			fallthrough
+		case eof, '\n':
+			return l.errorf("unterminated quoted string")
+		case '"':
+			break Loop
+		}
+	}
+	l.emit(itemString)
+	return lexInsideAction
+}
+
+// lexRawQuote scans a raw quoted string.
+func lexRawQuote(l *lexer) stateFn {
+Loop:
+	for {
+		switch l.next() {
+		case eof, '\n':
+			return l.errorf("unterminated raw quoted string")
+		case '`':
+			break Loop
+		}
+	}
+	l.emit(itemRawString)
+	return lexInsideAction
+}
+
+// isSpace reports whether r is a space character.
+func isSpace(r rune) bool {
+	return r == ' ' || r == '\t'
+}
+
+// isEndOfLine reports whether r is an end-of-line character.
+func isEndOfLine(r rune) bool {
+	return r == '\r' || r == '\n'
+}
+
+// isAlphaNumeric reports whether r is an alphabetic, digit, or underscore.
+func isAlphaNumeric(r rune) bool {
+	return r == '_' || unicode.IsLetter(r) || unicode.IsDigit(r)
+}
diff --git a/src/text/template/parse/lex_test.go b/src/text/template/parse/lex_test.go
new file mode 100644
index 000000000..d251ccffb
--- /dev/null
+++ b/src/text/template/parse/lex_test.go
@@ -0,0 +1,465 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"fmt"
+	"testing"
+)
+
+// Make the types prettyprint.
+var itemName = map[itemType]string{
+	itemError:        "error",
+	itemBool:         "bool",
+	itemChar:         "char",
+	itemCharConstant: "charconst",
+	itemComplex:      "complex",
+	itemColonEquals:  ":=",
+	itemEOF:          "EOF",
+	itemField:        "field",
+	itemIdentifier:   "identifier",
+	itemLeftDelim:    "left delim",
+	itemLeftParen:    "(",
+	itemNumber:       "number",
+	itemPipe:         "pipe",
+	itemRawString:    "raw string",
+	itemRightDelim:   "right delim",
+	itemRightParen:   ")",
+	itemSpace:        "space",
+	itemString:       "string",
+	itemVariable:     "variable",
+
+	// keywords
+	itemDot:      ".",
+	itemDefine:   "define",
+	itemElse:     "else",
+	itemIf:       "if",
+	itemEnd:      "end",
+	itemNil:      "nil",
+	itemRange:    "range",
+	itemTemplate: "template",
+	itemWith:     "with",
+}
+
+func (i itemType) String() string {
+	s := itemName[i]
+	if s == "" {
+		return fmt.Sprintf("item%d", int(i))
+	}
+	return s
+}
+
+type lexTest struct {
+	name  string
+	input string
+	items []item
+}
+
+var (
+	tEOF      = item{itemEOF, 0, ""}
+	tFor      = item{itemIdentifier, 0, "for"}
+	tLeft     = item{itemLeftDelim, 0, "{{"}
+	tLpar     = item{itemLeftParen, 0, "("}
+	tPipe     = item{itemPipe, 0, "|"}
+	tQuote    = item{itemString, 0, `"abc \n\t\" "`}
+	tRange    = item{itemRange, 0, "range"}
+	tRight    = item{itemRightDelim, 0, "}}"}
+	tRpar     = item{itemRightParen, 0, ")"}
+	tSpace    = item{itemSpace, 0, " "}
+	raw       = "`" + `abc\n\t\" ` + "`"
+	tRawQuote = item{itemRawString, 0, raw}
+)
+
+var lexTests = []lexTest{
+	{"empty", "", []item{tEOF}},
+	{"spaces", " \t\n", []item{{itemText, 0, " \t\n"}, tEOF}},
+	{"text", `now is the time`, []item{{itemText, 0, "now is the time"}, tEOF}},
+	{"text with comment", "hello-{{/* this is a comment */}}-world", []item{
+		{itemText, 0, "hello-"},
+		{itemText, 0, "-world"},
+		tEOF,
+	}},
+	{"punctuation", "{{,@% }}", []item{
+		tLeft,
+		{itemChar, 0, ","},
+		{itemChar, 0, "@"},
+		{itemChar, 0, "%"},
+		tSpace,
+		tRight,
+		tEOF,
+	}},
+	{"parens", "{{((3))}}", []item{
+		tLeft,
+		tLpar,
+		tLpar,
+		{itemNumber, 0, "3"},
+		tRpar,
+		tRpar,
+		tRight,
+		tEOF,
+	}},
+	{"empty action", `{{}}`, []item{tLeft, tRight, tEOF}},
+	{"for", `{{for}}`, []item{tLeft, tFor, tRight, tEOF}},
+	{"quote", `{{"abc \n\t\" "}}`, []item{tLeft, tQuote, tRight, tEOF}},
+	{"raw quote", "{{" + raw + "}}", []item{tLeft, tRawQuote, tRight, tEOF}},
+	{"numbers", "{{1 02 0x14 -7.2i 1e3 +1.2e-4 4.2i 1+2i}}", []item{
+		tLeft,
+		{itemNumber, 0, "1"},
+		tSpace,
+		{itemNumber, 0, "02"},
+		tSpace,
+		{itemNumber, 0, "0x14"},
+		tSpace,
+		{itemNumber, 0, "-7.2i"},
+		tSpace,
+		{itemNumber, 0, "1e3"},
+		tSpace,
+		{itemNumber, 0, "+1.2e-4"},
+		tSpace,
+		{itemNumber, 0, "4.2i"},
+		tSpace,
+		{itemComplex, 0, "1+2i"},
+		tRight,
+		tEOF,
+	}},
+	{"characters", `{{'a' '\n' '\'' '\\' '\u00FF' '\xFF' '本'}}`, []item{
+		tLeft,
+		{itemCharConstant, 0, `'a'`},
+		tSpace,
+		{itemCharConstant, 0, `'\n'`},
+		tSpace,
+		{itemCharConstant, 0, `'\''`},
+		tSpace,
+		{itemCharConstant, 0, `'\\'`},
+		tSpace,
+		{itemCharConstant, 0, `'\u00FF'`},
+		tSpace,
+		{itemCharConstant, 0, `'\xFF'`},
+		tSpace,
+		{itemCharConstant, 0, `'本'`},
+		tRight,
+		tEOF,
+	}},
+	{"bools", "{{true false}}", []item{
+		tLeft,
+		{itemBool, 0, "true"},
+		tSpace,
+		{itemBool, 0, "false"},
+		tRight,
+		tEOF,
+	}},
+	{"dot", "{{.}}", []item{
+		tLeft,
+		{itemDot, 0, "."},
+		tRight,
+		tEOF,
+	}},
+	{"nil", "{{nil}}", []item{
+		tLeft,
+		{itemNil, 0, "nil"},
+		tRight,
+		tEOF,
+	}},
+	{"dots", "{{.x . .2 .x.y.z}}", []item{
+		tLeft,
+		{itemField, 0, ".x"},
+		tSpace,
+		{itemDot, 0, "."},
+		tSpace,
+		{itemNumber, 0, ".2"},
+		tSpace,
+		{itemField, 0, ".x"},
+		{itemField, 0, ".y"},
+		{itemField, 0, ".z"},
+		tRight,
+		tEOF,
+	}},
+	{"keywords", "{{range if else end with}}", []item{
+		tLeft,
+		{itemRange, 0, "range"},
+		tSpace,
+		{itemIf, 0, "if"},
+		tSpace,
+		{itemElse, 0, "else"},
+		tSpace,
+		{itemEnd, 0, "end"},
+		tSpace,
+		{itemWith, 0, "with"},
+		tRight,
+		tEOF,
+	}},
+	{"variables", "{{$c := printf $ $hello $23 $ $var.Field .Method}}", []item{
+		tLeft,
+		{itemVariable, 0, "$c"},
+		tSpace,
+		{itemColonEquals, 0, ":="},
+		tSpace,
+		{itemIdentifier, 0, "printf"},
+		tSpace,
+		{itemVariable, 0, "$"},
+		tSpace,
+		{itemVariable, 0, "$hello"},
+		tSpace,
+		{itemVariable, 0, "$23"},
+		tSpace,
+		{itemVariable, 0, "$"},
+		tSpace,
+		{itemVariable, 0, "$var"},
+		{itemField, 0, ".Field"},
+		tSpace,
+		{itemField, 0, ".Method"},
+		tRight,
+		tEOF,
+	}},
+	{"variable invocation", "{{$x 23}}", []item{
+		tLeft,
+		{itemVariable, 0, "$x"},
+		tSpace,
+		{itemNumber, 0, "23"},
+		tRight,
+		tEOF,
+	}},
+	{"pipeline", `intro {{echo hi 1.2 |noargs|args 1 "hi"}} outro`, []item{
+		{itemText, 0, "intro "},
+		tLeft,
+		{itemIdentifier, 0, "echo"},
+		tSpace,
+		{itemIdentifier, 0, "hi"},
+		tSpace,
+		{itemNumber, 0, "1.2"},
+		tSpace,
+		tPipe,
+		{itemIdentifier, 0, "noargs"},
+		tPipe,
+		{itemIdentifier, 0, "args"},
+		tSpace,
+		{itemNumber, 0, "1"},
+		tSpace,
+		{itemString, 0, `"hi"`},
+		tRight,
+		{itemText, 0, " outro"},
+		tEOF,
+	}},
+	{"declaration", "{{$v := 3}}", []item{
+		tLeft,
+		{itemVariable, 0, "$v"},
+		tSpace,
+		{itemColonEquals, 0, ":="},
+		tSpace,
+		{itemNumber, 0, "3"},
+		tRight,
+		tEOF,
+	}},
+	{"2 declarations", "{{$v , $w := 3}}", []item{
+		tLeft,
+		{itemVariable, 0, "$v"},
+		tSpace,
+		{itemChar, 0, ","},
+		tSpace,
+		{itemVariable, 0, "$w"},
+		tSpace,
+		{itemColonEquals, 0, ":="},
+		tSpace,
+		{itemNumber, 0, "3"},
+		tRight,
+		tEOF,
+	}},
+	{"field of parenthesized expression", "{{(.X).Y}}", []item{
+		tLeft,
+		tLpar,
+		{itemField, 0, ".X"},
+		tRpar,
+		{itemField, 0, ".Y"},
+		tRight,
+		tEOF,
+	}},
+	// errors
+	{"badchar", "#{{\x01}}", []item{
+		{itemText, 0, "#"},
+		tLeft,
+		{itemError, 0, "unrecognized character in action: U+0001"},
+	}},
+	{"unclosed action", "{{\n}}", []item{
+		tLeft,
+		{itemError, 0, "unclosed action"},
+	}},
+	{"EOF in action", "{{range", []item{
+		tLeft,
+		tRange,
+		{itemError, 0, "unclosed action"},
+	}},
+	{"unclosed quote", "{{\"\n\"}}", []item{
+		tLeft,
+		{itemError, 0, "unterminated quoted string"},
+	}},
+	{"unclosed raw quote", "{{`xx\n`}}", []item{
+		tLeft,
+		{itemError, 0, "unterminated raw quoted string"},
+	}},
+	{"unclosed char constant", "{{'\n}}", []item{
+		tLeft,
+		{itemError, 0, "unterminated character constant"},
+	}},
+	{"bad number", "{{3k}}", []item{
+		tLeft,
+		{itemError, 0, `bad number syntax: "3k"`},
+	}},
+	{"unclosed paren", "{{(3}}", []item{
+		tLeft,
+		tLpar,
+		{itemNumber, 0, "3"},
+		{itemError, 0, `unclosed left paren`},
+	}},
+	{"extra right paren", "{{3)}}", []item{
+		tLeft,
+		{itemNumber, 0, "3"},
+		tRpar,
+		{itemError, 0, `unexpected right paren U+0029 ')'`},
+	}},
+
+	// Fixed bugs
+	// Many elements in an action blew the lookahead until
+	// we made lexInsideAction not loop.
+	{"long pipeline deadlock", "{{|||||}}", []item{
+		tLeft,
+		tPipe,
+		tPipe,
+		tPipe,
+		tPipe,
+		tPipe,
+		tRight,
+		tEOF,
+	}},
+	{"text with bad comment", "hello-{{/*/}}-world", []item{
+		{itemText, 0, "hello-"},
+		{itemError, 0, `unclosed comment`},
+	}},
+	{"text with comment close separted from delim", "hello-{{/* */ }}-world", []item{
+		{itemText, 0, "hello-"},
+		{itemError, 0, `comment ends before closing delimiter`},
+	}},
+	// This one is an error that we can't catch because it breaks templates with
+	// minimized JavaScript. Should have fixed it before Go 1.1.
+	{"unmatched right delimiter", "hello-{.}}-world", []item{
+		{itemText, 0, "hello-{.}}-world"},
+		tEOF,
+	}},
+}
+
+// collect gathers the emitted items into a slice.
+func collect(t *lexTest, left, right string) (items []item) {
+	l := lex(t.name, t.input, left, right)
+	for {
+		item := l.nextItem()
+		items = append(items, item)
+		if item.typ == itemEOF || item.typ == itemError {
+			break
+		}
+	}
+	return
+}
+
+func equal(i1, i2 []item, checkPos bool) bool {
+	if len(i1) != len(i2) {
+		return false
+	}
+	for k := range i1 {
+		if i1[k].typ != i2[k].typ {
+			return false
+		}
+		if i1[k].val != i2[k].val {
+			return false
+		}
+		if checkPos && i1[k].pos != i2[k].pos {
+			return false
+		}
+	}
+	return true
+}
+
+func TestLex(t *testing.T) {
+	for _, test := range lexTests {
+		items := collect(&test, "", "")
+		if !equal(items, test.items, false) {
+			t.Errorf("%s: got\n\t%+v\nexpected\n\t%v", test.name, items, test.items)
+		}
+	}
+}
+
+// Some easy cases from above, but with delimiters $$ and @@
+var lexDelimTests = []lexTest{
+	{"punctuation", "$$,@%{{}}@@", []item{
+		tLeftDelim,
+		{itemChar, 0, ","},
+		{itemChar, 0, "@"},
+		{itemChar, 0, "%"},
+		{itemChar, 0, "{"},
+		{itemChar, 0, "{"},
+		{itemChar, 0, "}"},
+		{itemChar, 0, "}"},
+		tRightDelim,
+		tEOF,
+	}},
+	{"empty action", `$$@@`, []item{tLeftDelim, tRightDelim, tEOF}},
+	{"for", `$$for@@`, []item{tLeftDelim, tFor, tRightDelim, tEOF}},
+	{"quote", `$$"abc \n\t\" "@@`, []item{tLeftDelim, tQuote, tRightDelim, tEOF}},
+	{"raw quote", "$$" + raw + "@@", []item{tLeftDelim, tRawQuote, tRightDelim, tEOF}},
+}
+
+var (
+	tLeftDelim  = item{itemLeftDelim, 0, "$$"}
+	tRightDelim = item{itemRightDelim, 0, "@@"}
+)
+
+func TestDelims(t *testing.T) {
+	for _, test := range lexDelimTests {
+		items := collect(&test, "$$", "@@")
+		if !equal(items, test.items, false) {
+			t.Errorf("%s: got\n\t%v\nexpected\n\t%v", test.name, items, test.items)
+		}
+	}
+}
+
+var lexPosTests = []lexTest{
+	{"empty", "", []item{tEOF}},
+	{"punctuation", "{{,@%#}}", []item{
+		{itemLeftDelim, 0, "{{"},
+		{itemChar, 2, ","},
+		{itemChar, 3, "@"},
+		{itemChar, 4, "%"},
+		{itemChar, 5, "#"},
+		{itemRightDelim, 6, "}}"},
+		{itemEOF, 8, ""},
+	}},
+	{"sample", "0123{{hello}}xyz", []item{
+		{itemText, 0, "0123"},
+		{itemLeftDelim, 4, "{{"},
+		{itemIdentifier, 6, "hello"},
+		{itemRightDelim, 11, "}}"},
+		{itemText, 13, "xyz"},
+		{itemEOF, 16, ""},
+	}},
+}
+
+// The other tests don't check position, to make the test cases easier to construct.
+// This one does.
+func TestPos(t *testing.T) {
+	for _, test := range lexPosTests {
+		items := collect(&test, "", "")
+		if !equal(items, test.items, true) {
+			t.Errorf("%s: got\n\t%v\nexpected\n\t%v", test.name, items, test.items)
+			if len(items) == len(test.items) {
+				// Detailed print; avoid item.String() to expose the position value.
+				for i := range items {
+					if !equal(items[i:i+1], test.items[i:i+1], true) {
+						i1 := items[i]
+						i2 := test.items[i]
+						t.Errorf("\t#%d: got {%v %d %q} expected  {%v %d %q}", i, i1.typ, i1.pos, i1.val, i2.typ, i2.pos, i2.val)
+					}
+				}
+			}
+		}
+	}
+}
diff --git a/src/text/template/parse/node.go b/src/text/template/parse/node.go
new file mode 100644
index 000000000..55c37f6db
--- /dev/null
+++ b/src/text/template/parse/node.go
@@ -0,0 +1,834 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Parse nodes.
+
+package parse
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+var textFormat = "%s" // Changed to "%q" in tests for better error messages.
+
+// A Node is an element in the parse tree. The interface is trivial.
+// The interface contains an unexported method so that only
+// types local to this package can satisfy it.
+type Node interface {
+	Type() NodeType
+	String() string
+	// Copy does a deep copy of the Node and all its components.
+	// To avoid type assertions, some XxxNodes also have specialized
+	// CopyXxx methods that return *XxxNode.
+	Copy() Node
+	Position() Pos // byte position of start of node in full original input string
+	// tree returns the containing *Tree.
+	// It is unexported so all implementations of Node are in this package.
+	tree() *Tree
+}
+
+// NodeType identifies the type of a parse tree node.
+type NodeType int
+
+// Pos represents a byte position in the original input text from which
+// this template was parsed.
+type Pos int
+
+func (p Pos) Position() Pos {
+	return p
+}
+
+// Type returns itself and provides an easy default implementation
+// for embedding in a Node. Embedded in all non-trivial Nodes.
+func (t NodeType) Type() NodeType {
+	return t
+}
+
+const (
+	NodeText       NodeType = iota // Plain text.
+	NodeAction                     // A non-control action such as a field evaluation.
+	NodeBool                       // A boolean constant.
+	NodeChain                      // A sequence of field accesses.
+	NodeCommand                    // An element of a pipeline.
+	NodeDot                        // The cursor, dot.
+	nodeElse                       // An else action. Not added to tree.
+	nodeEnd                        // An end action. Not added to tree.
+	NodeField                      // A field or method name.
+	NodeIdentifier                 // An identifier; always a function name.
+	NodeIf                         // An if action.
+	NodeList                       // A list of Nodes.
+	NodeNil                        // An untyped nil constant.
+	NodeNumber                     // A numerical constant.
+	NodePipe                       // A pipeline of commands.
+	NodeRange                      // A range action.
+	NodeString                     // A string constant.
+	NodeTemplate                   // A template invocation action.
+	NodeVariable                   // A $ variable.
+	NodeWith                       // A with action.
+)
+
+// Nodes.
+
+// ListNode holds a sequence of nodes.
+type ListNode struct {
+	NodeType
+	Pos
+	tr    *Tree
+	Nodes []Node // The element nodes in lexical order.
+}
+
+func (t *Tree) newList(pos Pos) *ListNode {
+	return &ListNode{tr: t, NodeType: NodeList, Pos: pos}
+}
+
+func (l *ListNode) append(n Node) {
+	l.Nodes = append(l.Nodes, n)
+}
+
+func (l *ListNode) tree() *Tree {
+	return l.tr
+}
+
+func (l *ListNode) String() string {
+	b := new(bytes.Buffer)
+	for _, n := range l.Nodes {
+		fmt.Fprint(b, n)
+	}
+	return b.String()
+}
+
+func (l *ListNode) CopyList() *ListNode {
+	if l == nil {
+		return l
+	}
+	n := l.tr.newList(l.Pos)
+	for _, elem := range l.Nodes {
+		n.append(elem.Copy())
+	}
+	return n
+}
+
+func (l *ListNode) Copy() Node {
+	return l.CopyList()
+}
+
+// TextNode holds plain text.
+type TextNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Text []byte // The text; may span newlines.
+}
+
+func (t *Tree) newText(pos Pos, text string) *TextNode {
+	return &TextNode{tr: t, NodeType: NodeText, Pos: pos, Text: []byte(text)}
+}
+
+func (t *TextNode) String() string {
+	return fmt.Sprintf(textFormat, t.Text)
+}
+
+func (t *TextNode) tree() *Tree {
+	return t.tr
+}
+
+func (t *TextNode) Copy() Node {
+	return &TextNode{tr: t.tr, NodeType: NodeText, Pos: t.Pos, Text: append([]byte{}, t.Text...)}
+}
+
+// PipeNode holds a pipeline with optional declaration
+type PipeNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Line int             // The line number in the input (deprecated; kept for compatibility)
+	Decl []*VariableNode // Variable declarations in lexical order.
+	Cmds []*CommandNode  // The commands in lexical order.
+}
+
+func (t *Tree) newPipeline(pos Pos, line int, decl []*VariableNode) *PipeNode {
+	return &PipeNode{tr: t, NodeType: NodePipe, Pos: pos, Line: line, Decl: decl}
+}
+
+func (p *PipeNode) append(command *CommandNode) {
+	p.Cmds = append(p.Cmds, command)
+}
+
+func (p *PipeNode) String() string {
+	s := ""
+	if len(p.Decl) > 0 {
+		for i, v := range p.Decl {
+			if i > 0 {
+				s += ", "
+			}
+			s += v.String()
+		}
+		s += " := "
+	}
+	for i, c := range p.Cmds {
+		if i > 0 {
+			s += " | "
+		}
+		s += c.String()
+	}
+	return s
+}
+
+func (p *PipeNode) tree() *Tree {
+	return p.tr
+}
+
+func (p *PipeNode) CopyPipe() *PipeNode {
+	if p == nil {
+		return p
+	}
+	var decl []*VariableNode
+	for _, d := range p.Decl {
+		decl = append(decl, d.Copy().(*VariableNode))
+	}
+	n := p.tr.newPipeline(p.Pos, p.Line, decl)
+	for _, c := range p.Cmds {
+		n.append(c.Copy().(*CommandNode))
+	}
+	return n
+}
+
+func (p *PipeNode) Copy() Node {
+	return p.CopyPipe()
+}
+
+// ActionNode holds an action (something bounded by delimiters).
+// Control actions have their own nodes; ActionNode represents simple
+// ones such as field evaluations and parenthesized pipelines.
+type ActionNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Line int       // The line number in the input (deprecated; kept for compatibility)
+	Pipe *PipeNode // The pipeline in the action.
+}
+
+func (t *Tree) newAction(pos Pos, line int, pipe *PipeNode) *ActionNode {
+	return &ActionNode{tr: t, NodeType: NodeAction, Pos: pos, Line: line, Pipe: pipe}
+}
+
+func (a *ActionNode) String() string {
+	return fmt.Sprintf("{{%s}}", a.Pipe)
+
+}
+
+func (a *ActionNode) tree() *Tree {
+	return a.tr
+}
+
+func (a *ActionNode) Copy() Node {
+	return a.tr.newAction(a.Pos, a.Line, a.Pipe.CopyPipe())
+
+}
+
+// CommandNode holds a command (a pipeline inside an evaluating action).
+type CommandNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Args []Node // Arguments in lexical order: Identifier, field, or constant.
+}
+
+func (t *Tree) newCommand(pos Pos) *CommandNode {
+	return &CommandNode{tr: t, NodeType: NodeCommand, Pos: pos}
+}
+
+func (c *CommandNode) append(arg Node) {
+	c.Args = append(c.Args, arg)
+}
+
+func (c *CommandNode) String() string {
+	s := ""
+	for i, arg := range c.Args {
+		if i > 0 {
+			s += " "
+		}
+		if arg, ok := arg.(*PipeNode); ok {
+			s += "(" + arg.String() + ")"
+			continue
+		}
+		s += arg.String()
+	}
+	return s
+}
+
+func (c *CommandNode) tree() *Tree {
+	return c.tr
+}
+
+func (c *CommandNode) Copy() Node {
+	if c == nil {
+		return c
+	}
+	n := c.tr.newCommand(c.Pos)
+	for _, c := range c.Args {
+		n.append(c.Copy())
+	}
+	return n
+}
+
+// IdentifierNode holds an identifier.
+type IdentifierNode struct {
+	NodeType
+	Pos
+	tr    *Tree
+	Ident string // The identifier's name.
+}
+
+// NewIdentifier returns a new IdentifierNode with the given identifier name.
+func NewIdentifier(ident string) *IdentifierNode {
+	return &IdentifierNode{NodeType: NodeIdentifier, Ident: ident}
+}
+
+// SetPos sets the position. NewIdentifier is a public method so we can't modify its signature.
+// Chained for convenience.
+// TODO: fix one day?
+func (i *IdentifierNode) SetPos(pos Pos) *IdentifierNode {
+	i.Pos = pos
+	return i
+}
+
+// SetTree sets the parent tree for the node. NewIdentifier is a public method so we can't modify its signature.
+// Chained for convenience.
+// TODO: fix one day?
+func (i *IdentifierNode) SetTree(t *Tree) *IdentifierNode {
+	i.tr = t
+	return i
+}
+
+func (i *IdentifierNode) String() string {
+	return i.Ident
+}
+
+func (i *IdentifierNode) tree() *Tree {
+	return i.tr
+}
+
+func (i *IdentifierNode) Copy() Node {
+	return NewIdentifier(i.Ident).SetTree(i.tr).SetPos(i.Pos)
+}
+
+// VariableNode holds a list of variable names, possibly with chained field
+// accesses. The dollar sign is part of the (first) name.
+type VariableNode struct {
+	NodeType
+	Pos
+	tr    *Tree
+	Ident []string // Variable name and fields in lexical order.
+}
+
+func (t *Tree) newVariable(pos Pos, ident string) *VariableNode {
+	return &VariableNode{tr: t, NodeType: NodeVariable, Pos: pos, Ident: strings.Split(ident, ".")}
+}
+
+func (v *VariableNode) String() string {
+	s := ""
+	for i, id := range v.Ident {
+		if i > 0 {
+			s += "."
+		}
+		s += id
+	}
+	return s
+}
+
+func (v *VariableNode) tree() *Tree {
+	return v.tr
+}
+
+func (v *VariableNode) Copy() Node {
+	return &VariableNode{tr: v.tr, NodeType: NodeVariable, Pos: v.Pos, Ident: append([]string{}, v.Ident...)}
+}
+
+// DotNode holds the special identifier '.'.
+type DotNode struct {
+	NodeType
+	Pos
+	tr *Tree
+}
+
+func (t *Tree) newDot(pos Pos) *DotNode {
+	return &DotNode{tr: t, NodeType: NodeDot, Pos: pos}
+}
+
+func (d *DotNode) Type() NodeType {
+	// Override method on embedded NodeType for API compatibility.
+	// TODO: Not really a problem; could change API without effect but
+	// api tool complains.
+	return NodeDot
+}
+
+func (d *DotNode) String() string {
+	return "."
+}
+
+func (d *DotNode) tree() *Tree {
+	return d.tr
+}
+
+func (d *DotNode) Copy() Node {
+	return d.tr.newDot(d.Pos)
+}
+
+// NilNode holds the special identifier 'nil' representing an untyped nil constant.
+type NilNode struct {
+	NodeType
+	Pos
+	tr *Tree
+}
+
+func (t *Tree) newNil(pos Pos) *NilNode {
+	return &NilNode{tr: t, NodeType: NodeNil, Pos: pos}
+}
+
+func (n *NilNode) Type() NodeType {
+	// Override method on embedded NodeType for API compatibility.
+	// TODO: Not really a problem; could change API without effect but
+	// api tool complains.
+	return NodeNil
+}
+
+func (n *NilNode) String() string {
+	return "nil"
+}
+
+func (n *NilNode) tree() *Tree {
+	return n.tr
+}
+
+func (n *NilNode) Copy() Node {
+	return n.tr.newNil(n.Pos)
+}
+
+// FieldNode holds a field (identifier starting with '.').
+// The names may be chained ('.x.y').
+// The period is dropped from each ident.
+type FieldNode struct {
+	NodeType
+	Pos
+	tr    *Tree
+	Ident []string // The identifiers in lexical order.
+}
+
+func (t *Tree) newField(pos Pos, ident string) *FieldNode {
+	return &FieldNode{tr: t, NodeType: NodeField, Pos: pos, Ident: strings.Split(ident[1:], ".")} // [1:] to drop leading period
+}
+
+func (f *FieldNode) String() string {
+	s := ""
+	for _, id := range f.Ident {
+		s += "." + id
+	}
+	return s
+}
+
+func (f *FieldNode) tree() *Tree {
+	return f.tr
+}
+
+func (f *FieldNode) Copy() Node {
+	return &FieldNode{tr: f.tr, NodeType: NodeField, Pos: f.Pos, Ident: append([]string{}, f.Ident...)}
+}
+
+// ChainNode holds a term followed by a chain of field accesses (identifier starting with '.').
+// The names may be chained ('.x.y').
+// The periods are dropped from each ident.
+type ChainNode struct {
+	NodeType
+	Pos
+	tr    *Tree
+	Node  Node
+	Field []string // The identifiers in lexical order.
+}
+
+func (t *Tree) newChain(pos Pos, node Node) *ChainNode {
+	return &ChainNode{tr: t, NodeType: NodeChain, Pos: pos, Node: node}
+}
+
+// Add adds the named field (which should start with a period) to the end of the chain.
+func (c *ChainNode) Add(field string) {
+	if len(field) == 0 || field[0] != '.' {
+		panic("no dot in field")
+	}
+	field = field[1:] // Remove leading dot.
+	if field == "" {
+		panic("empty field")
+	}
+	c.Field = append(c.Field, field)
+}
+
+func (c *ChainNode) String() string {
+	s := c.Node.String()
+	if _, ok := c.Node.(*PipeNode); ok {
+		s = "(" + s + ")"
+	}
+	for _, field := range c.Field {
+		s += "." + field
+	}
+	return s
+}
+
+func (c *ChainNode) tree() *Tree {
+	return c.tr
+}
+
+func (c *ChainNode) Copy() Node {
+	return &ChainNode{tr: c.tr, NodeType: NodeChain, Pos: c.Pos, Node: c.Node, Field: append([]string{}, c.Field...)}
+}
+
+// BoolNode holds a boolean constant.
+type BoolNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	True bool // The value of the boolean constant.
+}
+
+func (t *Tree) newBool(pos Pos, true bool) *BoolNode {
+	return &BoolNode{tr: t, NodeType: NodeBool, Pos: pos, True: true}
+}
+
+func (b *BoolNode) String() string {
+	if b.True {
+		return "true"
+	}
+	return "false"
+}
+
+func (b *BoolNode) tree() *Tree {
+	return b.tr
+}
+
+func (b *BoolNode) Copy() Node {
+	return b.tr.newBool(b.Pos, b.True)
+}
+
+// NumberNode holds a number: signed or unsigned integer, float, or complex.
+// The value is parsed and stored under all the types that can represent the value.
+// This simulates in a small amount of code the behavior of Go's ideal constants.
+type NumberNode struct {
+	NodeType
+	Pos
+	tr         *Tree
+	IsInt      bool       // Number has an integral value.
+	IsUint     bool       // Number has an unsigned integral value.
+	IsFloat    bool       // Number has a floating-point value.
+	IsComplex  bool       // Number is complex.
+	Int64      int64      // The signed integer value.
+	Uint64     uint64     // The unsigned integer value.
+	Float64    float64    // The floating-point value.
+	Complex128 complex128 // The complex value.
+	Text       string     // The original textual representation from the input.
+}
+
+func (t *Tree) newNumber(pos Pos, text string, typ itemType) (*NumberNode, error) {
+	n := &NumberNode{tr: t, NodeType: NodeNumber, Pos: pos, Text: text}
+	switch typ {
+	case itemCharConstant:
+		rune, _, tail, err := strconv.UnquoteChar(text[1:], text[0])
+		if err != nil {
+			return nil, err
+		}
+		if tail != "'" {
+			return nil, fmt.Errorf("malformed character constant: %s", text)
+		}
+		n.Int64 = int64(rune)
+		n.IsInt = true
+		n.Uint64 = uint64(rune)
+		n.IsUint = true
+		n.Float64 = float64(rune) // odd but those are the rules.
+		n.IsFloat = true
+		return n, nil
+	case itemComplex:
+		// fmt.Sscan can parse the pair, so let it do the work.
+		if _, err := fmt.Sscan(text, &n.Complex128); err != nil {
+			return nil, err
+		}
+		n.IsComplex = true
+		n.simplifyComplex()
+		return n, nil
+	}
+	// Imaginary constants can only be complex unless they are zero.
+	if len(text) > 0 && text[len(text)-1] == 'i' {
+		f, err := strconv.ParseFloat(text[:len(text)-1], 64)
+		if err == nil {
+			n.IsComplex = true
+			n.Complex128 = complex(0, f)
+			n.simplifyComplex()
+			return n, nil
+		}
+	}
+	// Do integer test first so we get 0x123 etc.
+	u, err := strconv.ParseUint(text, 0, 64) // will fail for -0; fixed below.
+	if err == nil {
+		n.IsUint = true
+		n.Uint64 = u
+	}
+	i, err := strconv.ParseInt(text, 0, 64)
+	if err == nil {
+		n.IsInt = true
+		n.Int64 = i
+		if i == 0 {
+			n.IsUint = true // in case of -0.
+			n.Uint64 = u
+		}
+	}
+	// If an integer extraction succeeded, promote the float.
+	if n.IsInt {
+		n.IsFloat = true
+		n.Float64 = float64(n.Int64)
+	} else if n.IsUint {
+		n.IsFloat = true
+		n.Float64 = float64(n.Uint64)
+	} else {
+		f, err := strconv.ParseFloat(text, 64)
+		if err == nil {
+			n.IsFloat = true
+			n.Float64 = f
+			// If a floating-point extraction succeeded, extract the int if needed.
+			if !n.IsInt && float64(int64(f)) == f {
+				n.IsInt = true
+				n.Int64 = int64(f)
+			}
+			if !n.IsUint && float64(uint64(f)) == f {
+				n.IsUint = true
+				n.Uint64 = uint64(f)
+			}
+		}
+	}
+	if !n.IsInt && !n.IsUint && !n.IsFloat {
+		return nil, fmt.Errorf("illegal number syntax: %q", text)
+	}
+	return n, nil
+}
+
+// simplifyComplex pulls out any other types that are represented by the complex number.
+// These all require that the imaginary part be zero.
+func (n *NumberNode) simplifyComplex() {
+	n.IsFloat = imag(n.Complex128) == 0
+	if n.IsFloat {
+		n.Float64 = real(n.Complex128)
+		n.IsInt = float64(int64(n.Float64)) == n.Float64
+		if n.IsInt {
+			n.Int64 = int64(n.Float64)
+		}
+		n.IsUint = float64(uint64(n.Float64)) == n.Float64
+		if n.IsUint {
+			n.Uint64 = uint64(n.Float64)
+		}
+	}
+}
+
+func (n *NumberNode) String() string {
+	return n.Text
+}
+
+func (n *NumberNode) tree() *Tree {
+	return n.tr
+}
+
+func (n *NumberNode) Copy() Node {
+	nn := new(NumberNode)
+	*nn = *n // Easy, fast, correct.
+	return nn
+}
+
+// StringNode holds a string constant. The value has been "unquoted".
+type StringNode struct {
+	NodeType
+	Pos
+	tr     *Tree
+	Quoted string // The original text of the string, with quotes.
+	Text   string // The string, after quote processing.
+}
+
+func (t *Tree) newString(pos Pos, orig, text string) *StringNode {
+	return &StringNode{tr: t, NodeType: NodeString, Pos: pos, Quoted: orig, Text: text}
+}
+
+func (s *StringNode) String() string {
+	return s.Quoted
+}
+
+func (s *StringNode) tree() *Tree {
+	return s.tr
+}
+
+func (s *StringNode) Copy() Node {
+	return s.tr.newString(s.Pos, s.Quoted, s.Text)
+}
+
+// endNode represents an {{end}} action.
+// It does not appear in the final parse tree.
+type endNode struct {
+	NodeType
+	Pos
+	tr *Tree
+}
+
+func (t *Tree) newEnd(pos Pos) *endNode {
+	return &endNode{tr: t, NodeType: nodeEnd, Pos: pos}
+}
+
+func (e *endNode) String() string {
+	return "{{end}}"
+}
+
+func (e *endNode) tree() *Tree {
+	return e.tr
+}
+
+func (e *endNode) Copy() Node {
+	return e.tr.newEnd(e.Pos)
+}
+
+// elseNode represents an {{else}} action. Does not appear in the final tree.
+type elseNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Line int // The line number in the input (deprecated; kept for compatibility)
+}
+
+func (t *Tree) newElse(pos Pos, line int) *elseNode {
+	return &elseNode{tr: t, NodeType: nodeElse, Pos: pos, Line: line}
+}
+
+func (e *elseNode) Type() NodeType {
+	return nodeElse
+}
+
+func (e *elseNode) String() string {
+	return "{{else}}"
+}
+
+func (e *elseNode) tree() *Tree {
+	return e.tr
+}
+
+func (e *elseNode) Copy() Node {
+	return e.tr.newElse(e.Pos, e.Line)
+}
+
+// BranchNode is the common representation of if, range, and with.
+type BranchNode struct {
+	NodeType
+	Pos
+	tr       *Tree
+	Line     int       // The line number in the input (deprecated; kept for compatibility)
+	Pipe     *PipeNode // The pipeline to be evaluated.
+	List     *ListNode // What to execute if the value is non-empty.
+	ElseList *ListNode // What to execute if the value is empty (nil if absent).
+}
+
+func (b *BranchNode) String() string {
+	name := ""
+	switch b.NodeType {
+	case NodeIf:
+		name = "if"
+	case NodeRange:
+		name = "range"
+	case NodeWith:
+		name = "with"
+	default:
+		panic("unknown branch type")
+	}
+	if b.ElseList != nil {
+		return fmt.Sprintf("{{%s %s}}%s{{else}}%s{{end}}", name, b.Pipe, b.List, b.ElseList)
+	}
+	return fmt.Sprintf("{{%s %s}}%s{{end}}", name, b.Pipe, b.List)
+}
+
+func (b *BranchNode) tree() *Tree {
+	return b.tr
+}
+
+func (b *BranchNode) Copy() Node {
+	switch b.NodeType {
+	case NodeIf:
+		return b.tr.newIf(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
+	case NodeRange:
+		return b.tr.newRange(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
+	case NodeWith:
+		return b.tr.newWith(b.Pos, b.Line, b.Pipe, b.List, b.ElseList)
+	default:
+		panic("unknown branch type")
+	}
+}
+
+// IfNode represents an {{if}} action and its commands.
+type IfNode struct {
+	BranchNode
+}
+
+func (t *Tree) newIf(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *IfNode {
+	return &IfNode{BranchNode{tr: t, NodeType: NodeIf, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
+}
+
+func (i *IfNode) Copy() Node {
+	return i.tr.newIf(i.Pos, i.Line, i.Pipe.CopyPipe(), i.List.CopyList(), i.ElseList.CopyList())
+}
+
+// RangeNode represents a {{range}} action and its commands.
+type RangeNode struct {
+	BranchNode
+}
+
+func (t *Tree) newRange(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *RangeNode {
+	return &RangeNode{BranchNode{tr: t, NodeType: NodeRange, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
+}
+
+func (r *RangeNode) Copy() Node {
+	return r.tr.newRange(r.Pos, r.Line, r.Pipe.CopyPipe(), r.List.CopyList(), r.ElseList.CopyList())
+}
+
+// WithNode represents a {{with}} action and its commands.
+type WithNode struct {
+	BranchNode
+}
+
+func (t *Tree) newWith(pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) *WithNode {
+	return &WithNode{BranchNode{tr: t, NodeType: NodeWith, Pos: pos, Line: line, Pipe: pipe, List: list, ElseList: elseList}}
+}
+
+func (w *WithNode) Copy() Node {
+	return w.tr.newWith(w.Pos, w.Line, w.Pipe.CopyPipe(), w.List.CopyList(), w.ElseList.CopyList())
+}
+
+// TemplateNode represents a {{template}} action.
+type TemplateNode struct {
+	NodeType
+	Pos
+	tr   *Tree
+	Line int       // The line number in the input (deprecated; kept for compatibility)
+	Name string    // The name of the template (unquoted).
+	Pipe *PipeNode // The command to evaluate as dot for the template.
+}
+
+func (t *Tree) newTemplate(pos Pos, line int, name string, pipe *PipeNode) *TemplateNode {
+	return &TemplateNode{tr: t, NodeType: NodeTemplate, Pos: pos, Line: line, Name: name, Pipe: pipe}
+}
+
+func (t *TemplateNode) String() string {
+	if t.Pipe == nil {
+		return fmt.Sprintf("{{template %q}}", t.Name)
+	}
+	return fmt.Sprintf("{{template %q %s}}", t.Name, t.Pipe)
+}
+
+func (t *TemplateNode) tree() *Tree {
+	return t.tr
+}
+
+func (t *TemplateNode) Copy() Node {
+	return t.tr.newTemplate(t.Pos, t.Line, t.Name, t.Pipe.CopyPipe())
+}
diff --git a/src/text/template/parse/parse.go b/src/text/template/parse/parse.go
new file mode 100644
index 000000000..af33880c1
--- /dev/null
+++ b/src/text/template/parse/parse.go
@@ -0,0 +1,677 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package parse builds parse trees for templates as defined by text/template
+// and html/template. Clients should use those packages to construct templates
+// rather than this one, which provides shared internal data structures not
+// intended for general use.
+package parse
+
+import (
+	"bytes"
+	"fmt"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+// Tree is the representation of a single parsed template.
+type Tree struct {
+	Name      string    // name of the template represented by the tree.
+	ParseName string    // name of the top-level template during parsing, for error messages.
+	Root      *ListNode // top-level root of the tree.
+	text      string    // text parsed to create the template (or its parent)
+	// Parsing only; cleared after parse.
+	funcs     []map[string]interface{}
+	lex       *lexer
+	token     [3]item // three-token lookahead for parser.
+	peekCount int
+	vars      []string // variables defined at the moment.
+}
+
+// Copy returns a copy of the Tree. Any parsing state is discarded.
+func (t *Tree) Copy() *Tree {
+	if t == nil {
+		return nil
+	}
+	return &Tree{
+		Name:      t.Name,
+		ParseName: t.ParseName,
+		Root:      t.Root.CopyList(),
+		text:      t.text,
+	}
+}
+
+// Parse returns a map from template name to parse.Tree, created by parsing the
+// templates described in the argument string. The top-level template will be
+// given the specified name. If an error is encountered, parsing stops and an
+// empty map is returned with the error.
+func Parse(name, text, leftDelim, rightDelim string, funcs ...map[string]interface{}) (treeSet map[string]*Tree, err error) {
+	treeSet = make(map[string]*Tree)
+	t := New(name)
+	t.text = text
+	_, err = t.Parse(text, leftDelim, rightDelim, treeSet, funcs...)
+	return
+}
+
+// next returns the next token.
+func (t *Tree) next() item {
+	if t.peekCount > 0 {
+		t.peekCount--
+	} else {
+		t.token[0] = t.lex.nextItem()
+	}
+	return t.token[t.peekCount]
+}
+
+// backup backs the input stream up one token.
+func (t *Tree) backup() {
+	t.peekCount++
+}
+
+// backup2 backs the input stream up two tokens.
+// The zeroth token is already there.
+func (t *Tree) backup2(t1 item) {
+	t.token[1] = t1
+	t.peekCount = 2
+}
+
+// backup3 backs the input stream up three tokens
+// The zeroth token is already there.
+func (t *Tree) backup3(t2, t1 item) { // Reverse order: we're pushing back.
+	t.token[1] = t1
+	t.token[2] = t2
+	t.peekCount = 3
+}
+
+// peek returns but does not consume the next token.
+func (t *Tree) peek() item {
+	if t.peekCount > 0 {
+		return t.token[t.peekCount-1]
+	}
+	t.peekCount = 1
+	t.token[0] = t.lex.nextItem()
+	return t.token[0]
+}
+
+// nextNonSpace returns the next non-space token.
+func (t *Tree) nextNonSpace() (token item) {
+	for {
+		token = t.next()
+		if token.typ != itemSpace {
+			break
+		}
+	}
+	return token
+}
+
+// peekNonSpace returns but does not consume the next non-space token.
+func (t *Tree) peekNonSpace() (token item) {
+	for {
+		token = t.next()
+		if token.typ != itemSpace {
+			break
+		}
+	}
+	t.backup()
+	return token
+}
+
+// Parsing.
+
+// New allocates a new parse tree with the given name.
+func New(name string, funcs ...map[string]interface{}) *Tree {
+	return &Tree{
+		Name:  name,
+		funcs: funcs,
+	}
+}
+
+// ErrorContext returns a textual representation of the location of the node in the input text.
+// The receiver is only used when the node does not have a pointer to the tree inside,
+// which can occur in old code.
+func (t *Tree) ErrorContext(n Node) (location, context string) {
+	pos := int(n.Position())
+	tree := n.tree()
+	if tree == nil {
+		tree = t
+	}
+	text := tree.text[:pos]
+	byteNum := strings.LastIndex(text, "\n")
+	if byteNum == -1 {
+		byteNum = pos // On first line.
+	} else {
+		byteNum++ // After the newline.
+		byteNum = pos - byteNum
+	}
+	lineNum := 1 + strings.Count(text, "\n")
+	context = n.String()
+	if len(context) > 20 {
+		context = fmt.Sprintf("%.20s...", context)
+	}
+	return fmt.Sprintf("%s:%d:%d", tree.ParseName, lineNum, byteNum), context
+}
+
+// errorf formats the error and terminates processing.
+func (t *Tree) errorf(format string, args ...interface{}) {
+	t.Root = nil
+	format = fmt.Sprintf("template: %s:%d: %s", t.ParseName, t.lex.lineNumber(), format)
+	panic(fmt.Errorf(format, args...))
+}
+
+// error terminates processing.
+func (t *Tree) error(err error) {
+	t.errorf("%s", err)
+}
+
+// expect consumes the next token and guarantees it has the required type.
+func (t *Tree) expect(expected itemType, context string) item {
+	token := t.nextNonSpace()
+	if token.typ != expected {
+		t.unexpected(token, context)
+	}
+	return token
+}
+
+// expectOneOf consumes the next token and guarantees it has one of the required types.
+func (t *Tree) expectOneOf(expected1, expected2 itemType, context string) item {
+	token := t.nextNonSpace()
+	if token.typ != expected1 && token.typ != expected2 {
+		t.unexpected(token, context)
+	}
+	return token
+}
+
+// unexpected complains about the token and terminates processing.
+func (t *Tree) unexpected(token item, context string) {
+	t.errorf("unexpected %s in %s", token, context)
+}
+
+// recover is the handler that turns panics into returns from the top level of Parse.
+func (t *Tree) recover(errp *error) {
+	e := recover()
+	if e != nil {
+		if _, ok := e.(runtime.Error); ok {
+			panic(e)
+		}
+		if t != nil {
+			t.stopParse()
+		}
+		*errp = e.(error)
+	}
+	return
+}
+
+// startParse initializes the parser, using the lexer.
+func (t *Tree) startParse(funcs []map[string]interface{}, lex *lexer) {
+	t.Root = nil
+	t.lex = lex
+	t.vars = []string{"$"}
+	t.funcs = funcs
+}
+
+// stopParse terminates parsing.
+func (t *Tree) stopParse() {
+	t.lex = nil
+	t.vars = nil
+	t.funcs = nil
+}
+
+// Parse parses the template definition string to construct a representation of
+// the template for execution. If either action delimiter string is empty, the
+// default ("{{" or "}}") is used. Embedded template definitions are added to
+// the treeSet map.
+func (t *Tree) Parse(text, leftDelim, rightDelim string, treeSet map[string]*Tree, funcs ...map[string]interface{}) (tree *Tree, err error) {
+	defer t.recover(&err)
+	t.ParseName = t.Name
+	t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim))
+	t.text = text
+	t.parse(treeSet)
+	t.add(treeSet)
+	t.stopParse()
+	return t, nil
+}
+
+// add adds tree to the treeSet.
+func (t *Tree) add(treeSet map[string]*Tree) {
+	tree := treeSet[t.Name]
+	if tree == nil || IsEmptyTree(tree.Root) {
+		treeSet[t.Name] = t
+		return
+	}
+	if !IsEmptyTree(t.Root) {
+		t.errorf("template: multiple definition of template %q", t.Name)
+	}
+}
+
+// IsEmptyTree reports whether this tree (node) is empty of everything but space.
+func IsEmptyTree(n Node) bool {
+	switch n := n.(type) {
+	case nil:
+		return true
+	case *ActionNode:
+	case *IfNode:
+	case *ListNode:
+		for _, node := range n.Nodes {
+			if !IsEmptyTree(node) {
+				return false
+			}
+		}
+		return true
+	case *RangeNode:
+	case *TemplateNode:
+	case *TextNode:
+		return len(bytes.TrimSpace(n.Text)) == 0
+	case *WithNode:
+	default:
+		panic("unknown node: " + n.String())
+	}
+	return false
+}
+
+// parse is the top-level parser for a template, essentially the same
+// as itemList except it also parses {{define}} actions.
+// It runs to EOF.
+func (t *Tree) parse(treeSet map[string]*Tree) (next Node) {
+	t.Root = t.newList(t.peek().pos)
+	for t.peek().typ != itemEOF {
+		if t.peek().typ == itemLeftDelim {
+			delim := t.next()
+			if t.nextNonSpace().typ == itemDefine {
+				newT := New("definition") // name will be updated once we know it.
+				newT.text = t.text
+				newT.ParseName = t.ParseName
+				newT.startParse(t.funcs, t.lex)
+				newT.parseDefinition(treeSet)
+				continue
+			}
+			t.backup2(delim)
+		}
+		n := t.textOrAction()
+		if n.Type() == nodeEnd {
+			t.errorf("unexpected %s", n)
+		}
+		t.Root.append(n)
+	}
+	return nil
+}
+
+// parseDefinition parses a {{define}} ...  {{end}} template definition and
+// installs the definition in the treeSet map.  The "define" keyword has already
+// been scanned.
+func (t *Tree) parseDefinition(treeSet map[string]*Tree) {
+	const context = "define clause"
+	name := t.expectOneOf(itemString, itemRawString, context)
+	var err error
+	t.Name, err = strconv.Unquote(name.val)
+	if err != nil {
+		t.error(err)
+	}
+	t.expect(itemRightDelim, context)
+	var end Node
+	t.Root, end = t.itemList()
+	if end.Type() != nodeEnd {
+		t.errorf("unexpected %s in %s", end, context)
+	}
+	t.add(treeSet)
+	t.stopParse()
+}
+
+// itemList:
+//	textOrAction*
+// Terminates at {{end}} or {{else}}, returned separately.
+func (t *Tree) itemList() (list *ListNode, next Node) {
+	list = t.newList(t.peekNonSpace().pos)
+	for t.peekNonSpace().typ != itemEOF {
+		n := t.textOrAction()
+		switch n.Type() {
+		case nodeEnd, nodeElse:
+			return list, n
+		}
+		list.append(n)
+	}
+	t.errorf("unexpected EOF")
+	return
+}
+
+// textOrAction:
+//	text | action
+func (t *Tree) textOrAction() Node {
+	switch token := t.nextNonSpace(); token.typ {
+	case itemText:
+		return t.newText(token.pos, token.val)
+	case itemLeftDelim:
+		return t.action()
+	default:
+		t.unexpected(token, "input")
+	}
+	return nil
+}
+
+// Action:
+//	control
+//	command ("|" command)*
+// Left delim is past. Now get actions.
+// First word could be a keyword such as range.
+func (t *Tree) action() (n Node) {
+	switch token := t.nextNonSpace(); token.typ {
+	case itemElse:
+		return t.elseControl()
+	case itemEnd:
+		return t.endControl()
+	case itemIf:
+		return t.ifControl()
+	case itemRange:
+		return t.rangeControl()
+	case itemTemplate:
+		return t.templateControl()
+	case itemWith:
+		return t.withControl()
+	}
+	t.backup()
+	// Do not pop variables; they persist until "end".
+	return t.newAction(t.peek().pos, t.lex.lineNumber(), t.pipeline("command"))
+}
+
+// Pipeline:
+//	declarations? command ('|' command)*
+func (t *Tree) pipeline(context string) (pipe *PipeNode) {
+	var decl []*VariableNode
+	pos := t.peekNonSpace().pos
+	// Are there declarations?
+	for {
+		if v := t.peekNonSpace(); v.typ == itemVariable {
+			t.next()
+			// Since space is a token, we need 3-token look-ahead here in the worst case:
+			// in "$x foo" we need to read "foo" (as opposed to ":=") to know that $x is an
+			// argument variable rather than a declaration. So remember the token
+			// adjacent to the variable so we can push it back if necessary.
+			tokenAfterVariable := t.peek()
+			if next := t.peekNonSpace(); next.typ == itemColonEquals || (next.typ == itemChar && next.val == ",") {
+				t.nextNonSpace()
+				variable := t.newVariable(v.pos, v.val)
+				decl = append(decl, variable)
+				t.vars = append(t.vars, v.val)
+				if next.typ == itemChar && next.val == "," {
+					if context == "range" && len(decl) < 2 {
+						continue
+					}
+					t.errorf("too many declarations in %s", context)
+				}
+			} else if tokenAfterVariable.typ == itemSpace {
+				t.backup3(v, tokenAfterVariable)
+			} else {
+				t.backup2(v)
+			}
+		}
+		break
+	}
+	pipe = t.newPipeline(pos, t.lex.lineNumber(), decl)
+	for {
+		switch token := t.nextNonSpace(); token.typ {
+		case itemRightDelim, itemRightParen:
+			if len(pipe.Cmds) == 0 {
+				t.errorf("missing value for %s", context)
+			}
+			if token.typ == itemRightParen {
+				t.backup()
+			}
+			return
+		case itemBool, itemCharConstant, itemComplex, itemDot, itemField, itemIdentifier,
+			itemNumber, itemNil, itemRawString, itemString, itemVariable, itemLeftParen:
+			t.backup()
+			pipe.append(t.command())
+		default:
+			t.unexpected(token, context)
+		}
+	}
+}
+
+func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int, pipe *PipeNode, list, elseList *ListNode) {
+	defer t.popVars(len(t.vars))
+	line = t.lex.lineNumber()
+	pipe = t.pipeline(context)
+	var next Node
+	list, next = t.itemList()
+	switch next.Type() {
+	case nodeEnd: //done
+	case nodeElse:
+		if allowElseIf {
+			// Special case for "else if". If the "else" is followed immediately by an "if",
+			// the elseControl will have left the "if" token pending. Treat
+			//	{{if a}}_{{else if b}}_{{end}}
+			// as
+			//	{{if a}}_{{else}}{{if b}}_{{end}}{{end}}.
+			// To do this, parse the if as usual and stop at it {{end}}; the subsequent{{end}}
+			// is assumed. This technique works even for long if-else-if chains.
+			// TODO: Should we allow else-if in with and range?
+			if t.peek().typ == itemIf {
+				t.next() // Consume the "if" token.
+				elseList = t.newList(next.Position())
+				elseList.append(t.ifControl())
+				// Do not consume the next item - only one {{end}} required.
+				break
+			}
+		}
+		elseList, next = t.itemList()
+		if next.Type() != nodeEnd {
+			t.errorf("expected end; found %s", next)
+		}
+	}
+	return pipe.Position(), line, pipe, list, elseList
+}
+
+// If:
+//	{{if pipeline}} itemList {{end}}
+//	{{if pipeline}} itemList {{else}} itemList {{end}}
+// If keyword is past.
+func (t *Tree) ifControl() Node {
+	return t.newIf(t.parseControl(true, "if"))
+}
+
+// Range:
+//	{{range pipeline}} itemList {{end}}
+//	{{range pipeline}} itemList {{else}} itemList {{end}}
+// Range keyword is past.
+func (t *Tree) rangeControl() Node {
+	return t.newRange(t.parseControl(false, "range"))
+}
+
+// With:
+//	{{with pipeline}} itemList {{end}}
+//	{{with pipeline}} itemList {{else}} itemList {{end}}
+// If keyword is past.
+func (t *Tree) withControl() Node {
+	return t.newWith(t.parseControl(false, "with"))
+}
+
+// End:
+//	{{end}}
+// End keyword is past.
+func (t *Tree) endControl() Node {
+	return t.newEnd(t.expect(itemRightDelim, "end").pos)
+}
+
+// Else:
+//	{{else}}
+// Else keyword is past.
+func (t *Tree) elseControl() Node {
+	// Special case for "else if".
+	peek := t.peekNonSpace()
+	if peek.typ == itemIf {
+		// We see "{{else if ... " but in effect rewrite it to {{else}}{{if ... ".
+		return t.newElse(peek.pos, t.lex.lineNumber())
+	}
+	return t.newElse(t.expect(itemRightDelim, "else").pos, t.lex.lineNumber())
+}
+
+// Template:
+//	{{template stringValue pipeline}}
+// Template keyword is past.  The name must be something that can evaluate
+// to a string.
+func (t *Tree) templateControl() Node {
+	var name string
+	token := t.nextNonSpace()
+	switch token.typ {
+	case itemString, itemRawString:
+		s, err := strconv.Unquote(token.val)
+		if err != nil {
+			t.error(err)
+		}
+		name = s
+	default:
+		t.unexpected(token, "template invocation")
+	}
+	var pipe *PipeNode
+	if t.nextNonSpace().typ != itemRightDelim {
+		t.backup()
+		// Do not pop variables; they persist until "end".
+		pipe = t.pipeline("template")
+	}
+	return t.newTemplate(token.pos, t.lex.lineNumber(), name, pipe)
+}
+
+// command:
+//	operand (space operand)*
+// space-separated arguments up to a pipeline character or right delimiter.
+// we consume the pipe character but leave the right delim to terminate the action.
+func (t *Tree) command() *CommandNode {
+	cmd := t.newCommand(t.peekNonSpace().pos)
+	for {
+		t.peekNonSpace() // skip leading spaces.
+		operand := t.operand()
+		if operand != nil {
+			cmd.append(operand)
+		}
+		switch token := t.next(); token.typ {
+		case itemSpace:
+			continue
+		case itemError:
+			t.errorf("%s", token.val)
+		case itemRightDelim, itemRightParen:
+			t.backup()
+		case itemPipe:
+		default:
+			t.errorf("unexpected %s in operand; missing space?", token)
+		}
+		break
+	}
+	if len(cmd.Args) == 0 {
+		t.errorf("empty command")
+	}
+	return cmd
+}
+
+// operand:
+//	term .Field*
+// An operand is a space-separated component of a command,
+// a term possibly followed by field accesses.
+// A nil return means the next item is not an operand.
+func (t *Tree) operand() Node {
+	node := t.term()
+	if node == nil {
+		return nil
+	}
+	if t.peek().typ == itemField {
+		chain := t.newChain(t.peek().pos, node)
+		for t.peek().typ == itemField {
+			chain.Add(t.next().val)
+		}
+		// Compatibility with original API: If the term is of type NodeField
+		// or NodeVariable, just put more fields on the original.
+		// Otherwise, keep the Chain node.
+		// TODO: Switch to Chains always when we can.
+		switch node.Type() {
+		case NodeField:
+			node = t.newField(chain.Position(), chain.String())
+		case NodeVariable:
+			node = t.newVariable(chain.Position(), chain.String())
+		default:
+			node = chain
+		}
+	}
+	return node
+}
+
+// term:
+//	literal (number, string, nil, boolean)
+//	function (identifier)
+//	.
+//	.Field
+//	$
+//	'(' pipeline ')'
+// A term is a simple "expression".
+// A nil return means the next item is not a term.
+func (t *Tree) term() Node {
+	switch token := t.nextNonSpace(); token.typ {
+	case itemError:
+		t.errorf("%s", token.val)
+	case itemIdentifier:
+		if !t.hasFunction(token.val) {
+			t.errorf("function %q not defined", token.val)
+		}
+		return NewIdentifier(token.val).SetTree(t).SetPos(token.pos)
+	case itemDot:
+		return t.newDot(token.pos)
+	case itemNil:
+		return t.newNil(token.pos)
+	case itemVariable:
+		return t.useVar(token.pos, token.val)
+	case itemField:
+		return t.newField(token.pos, token.val)
+	case itemBool:
+		return t.newBool(token.pos, token.val == "true")
+	case itemCharConstant, itemComplex, itemNumber:
+		number, err := t.newNumber(token.pos, token.val, token.typ)
+		if err != nil {
+			t.error(err)
+		}
+		return number
+	case itemLeftParen:
+		pipe := t.pipeline("parenthesized pipeline")
+		if token := t.next(); token.typ != itemRightParen {
+			t.errorf("unclosed right paren: unexpected %s", token)
+		}
+		return pipe
+	case itemString, itemRawString:
+		s, err := strconv.Unquote(token.val)
+		if err != nil {
+			t.error(err)
+		}
+		return t.newString(token.pos, token.val, s)
+	}
+	t.backup()
+	return nil
+}
+
+// hasFunction reports if a function name exists in the Tree's maps.
+func (t *Tree) hasFunction(name string) bool {
+	for _, funcMap := range t.funcs {
+		if funcMap == nil {
+			continue
+		}
+		if funcMap[name] != nil {
+			return true
+		}
+	}
+	return false
+}
+
+// popVars trims the variable list to the specified length
+func (t *Tree) popVars(n int) {
+	t.vars = t.vars[:n]
+}
+
+// useVar returns a node for a variable reference. It errors if the
+// variable is not defined.
+func (t *Tree) useVar(pos Pos, name string) Node {
+	v := t.newVariable(pos, name)
+	for _, varName := range t.vars {
+		if varName == v.Ident[0] {
+			return v
+		}
+	}
+	t.errorf("undefined variable %q", v.Ident[0])
+	return nil
+}
diff --git a/src/text/template/parse/parse_test.go b/src/text/template/parse/parse_test.go
new file mode 100644
index 000000000..4a504fa7c
--- /dev/null
+++ b/src/text/template/parse/parse_test.go
@@ -0,0 +1,423 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package parse
+
+import (
+	"flag"
+	"fmt"
+	"strings"
+	"testing"
+)
+
+var debug = flag.Bool("debug", false, "show the errors produced by the main tests")
+
+type numberTest struct {
+	text      string
+	isInt     bool
+	isUint    bool
+	isFloat   bool
+	isComplex bool
+	int64
+	uint64
+	float64
+	complex128
+}
+
+var numberTests = []numberTest{
+	// basics
+	{"0", true, true, true, false, 0, 0, 0, 0},
+	{"-0", true, true, true, false, 0, 0, 0, 0}, // check that -0 is a uint.
+	{"73", true, true, true, false, 73, 73, 73, 0},
+	{"073", true, true, true, false, 073, 073, 073, 0},
+	{"0x73", true, true, true, false, 0x73, 0x73, 0x73, 0},
+	{"-73", true, false, true, false, -73, 0, -73, 0},
+	{"+73", true, false, true, false, 73, 0, 73, 0},
+	{"100", true, true, true, false, 100, 100, 100, 0},
+	{"1e9", true, true, true, false, 1e9, 1e9, 1e9, 0},
+	{"-1e9", true, false, true, false, -1e9, 0, -1e9, 0},
+	{"-1.2", false, false, true, false, 0, 0, -1.2, 0},
+	{"1e19", false, true, true, false, 0, 1e19, 1e19, 0},
+	{"-1e19", false, false, true, false, 0, 0, -1e19, 0},
+	{"4i", false, false, false, true, 0, 0, 0, 4i},
+	{"-1.2+4.2i", false, false, false, true, 0, 0, 0, -1.2 + 4.2i},
+	{"073i", false, false, false, true, 0, 0, 0, 73i}, // not octal!
+	// complex with 0 imaginary are float (and maybe integer)
+	{"0i", true, true, true, true, 0, 0, 0, 0},
+	{"-1.2+0i", false, false, true, true, 0, 0, -1.2, -1.2},
+	{"-12+0i", true, false, true, true, -12, 0, -12, -12},
+	{"13+0i", true, true, true, true, 13, 13, 13, 13},
+	// funny bases
+	{"0123", true, true, true, false, 0123, 0123, 0123, 0},
+	{"-0x0", true, true, true, false, 0, 0, 0, 0},
+	{"0xdeadbeef", true, true, true, false, 0xdeadbeef, 0xdeadbeef, 0xdeadbeef, 0},
+	// character constants
+	{`'a'`, true, true, true, false, 'a', 'a', 'a', 0},
+	{`'\n'`, true, true, true, false, '\n', '\n', '\n', 0},
+	{`'\\'`, true, true, true, false, '\\', '\\', '\\', 0},
+	{`'\''`, true, true, true, false, '\'', '\'', '\'', 0},
+	{`'\xFF'`, true, true, true, false, 0xFF, 0xFF, 0xFF, 0},
+	{`'パ'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	{`'\u30d1'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	{`'\U000030d1'`, true, true, true, false, 0x30d1, 0x30d1, 0x30d1, 0},
+	// some broken syntax
+	{text: "+-2"},
+	{text: "0x123."},
+	{text: "1e."},
+	{text: "0xi."},
+	{text: "1+2."},
+	{text: "'x"},
+	{text: "'xx'"},
+	// Issue 8622 - 0xe parsed as floating point. Very embarrassing.
+	{"0xef", true, true, true, false, 0xef, 0xef, 0xef, 0},
+}
+
+func TestNumberParse(t *testing.T) {
+	for _, test := range numberTests {
+		// If fmt.Sscan thinks it's complex, it's complex.  We can't trust the output
+		// because imaginary comes out as a number.
+		var c complex128
+		typ := itemNumber
+		var tree *Tree
+		if test.text[0] == '\'' {
+			typ = itemCharConstant
+		} else {
+			_, err := fmt.Sscan(test.text, &c)
+			if err == nil {
+				typ = itemComplex
+			}
+		}
+		n, err := tree.newNumber(0, test.text, typ)
+		ok := test.isInt || test.isUint || test.isFloat || test.isComplex
+		if ok && err != nil {
+			t.Errorf("unexpected error for %q: %s", test.text, err)
+			continue
+		}
+		if !ok && err == nil {
+			t.Errorf("expected error for %q", test.text)
+			continue
+		}
+		if !ok {
+			if *debug {
+				fmt.Printf("%s\n\t%s\n", test.text, err)
+			}
+			continue
+		}
+		if n.IsComplex != test.isComplex {
+			t.Errorf("complex incorrect for %q; should be %t", test.text, test.isComplex)
+		}
+		if test.isInt {
+			if !n.IsInt {
+				t.Errorf("expected integer for %q", test.text)
+			}
+			if n.Int64 != test.int64 {
+				t.Errorf("int64 for %q should be %d Is %d", test.text, test.int64, n.Int64)
+			}
+		} else if n.IsInt {
+			t.Errorf("did not expect integer for %q", test.text)
+		}
+		if test.isUint {
+			if !n.IsUint {
+				t.Errorf("expected unsigned integer for %q", test.text)
+			}
+			if n.Uint64 != test.uint64 {
+				t.Errorf("uint64 for %q should be %d Is %d", test.text, test.uint64, n.Uint64)
+			}
+		} else if n.IsUint {
+			t.Errorf("did not expect unsigned integer for %q", test.text)
+		}
+		if test.isFloat {
+			if !n.IsFloat {
+				t.Errorf("expected float for %q", test.text)
+			}
+			if n.Float64 != test.float64 {
+				t.Errorf("float64 for %q should be %g Is %g", test.text, test.float64, n.Float64)
+			}
+		} else if n.IsFloat {
+			t.Errorf("did not expect float for %q", test.text)
+		}
+		if test.isComplex {
+			if !n.IsComplex {
+				t.Errorf("expected complex for %q", test.text)
+			}
+			if n.Complex128 != test.complex128 {
+				t.Errorf("complex128 for %q should be %g Is %g", test.text, test.complex128, n.Complex128)
+			}
+		} else if n.IsComplex {
+			t.Errorf("did not expect complex for %q", test.text)
+		}
+	}
+}
+
+type parseTest struct {
+	name   string
+	input  string
+	ok     bool
+	result string // what the user would see in an error message.
+}
+
+const (
+	noError  = true
+	hasError = false
+)
+
+var parseTests = []parseTest{
+	{"empty", "", noError,
+		``},
+	{"comment", "{{/*\n\n\n*/}}", noError,
+		``},
+	{"spaces", " \t\n", noError,
+		`" \t\n"`},
+	{"text", "some text", noError,
+		`"some text"`},
+	{"emptyAction", "{{}}", hasError,
+		`{{}}`},
+	{"field", "{{.X}}", noError,
+		`{{.X}}`},
+	{"simple command", "{{printf}}", noError,
+		`{{printf}}`},
+	{"$ invocation", "{{$}}", noError,
+		"{{$}}"},
+	{"variable invocation", "{{with $x := 3}}{{$x 23}}{{end}}", noError,
+		"{{with $x := 3}}{{$x 23}}{{end}}"},
+	{"variable with fields", "{{$.I}}", noError,
+		"{{$.I}}"},
+	{"multi-word command", "{{printf `%d` 23}}", noError,
+		"{{printf `%d` 23}}"},
+	{"pipeline", "{{.X|.Y}}", noError,
+		`{{.X | .Y}}`},
+	{"pipeline with decl", "{{$x := .X|.Y}}", noError,
+		`{{$x := .X | .Y}}`},
+	{"nested pipeline", "{{.X (.Y .Z) (.A | .B .C) (.E)}}", noError,
+		`{{.X (.Y .Z) (.A | .B .C) (.E)}}`},
+	{"field applied to parentheses", "{{(.Y .Z).Field}}", noError,
+		`{{(.Y .Z).Field}}`},
+	{"simple if", "{{if .X}}hello{{end}}", noError,
+		`{{if .X}}"hello"{{end}}`},
+	{"if with else", "{{if .X}}true{{else}}false{{end}}", noError,
+		`{{if .X}}"true"{{else}}"false"{{end}}`},
+	{"if with else if", "{{if .X}}true{{else if .Y}}false{{end}}", noError,
+		`{{if .X}}"true"{{else}}{{if .Y}}"false"{{end}}{{end}}`},
+	{"if else chain", "+{{if .X}}X{{else if .Y}}Y{{else if .Z}}Z{{end}}+", noError,
+		`"+"{{if .X}}"X"{{else}}{{if .Y}}"Y"{{else}}{{if .Z}}"Z"{{end}}{{end}}{{end}}"+"`},
+	{"simple range", "{{range .X}}hello{{end}}", noError,
+		`{{range .X}}"hello"{{end}}`},
+	{"chained field range", "{{range .X.Y.Z}}hello{{end}}", noError,
+		`{{range .X.Y.Z}}"hello"{{end}}`},
+	{"nested range", "{{range .X}}hello{{range .Y}}goodbye{{end}}{{end}}", noError,
+		`{{range .X}}"hello"{{range .Y}}"goodbye"{{end}}{{end}}`},
+	{"range with else", "{{range .X}}true{{else}}false{{end}}", noError,
+		`{{range .X}}"true"{{else}}"false"{{end}}`},
+	{"range over pipeline", "{{range .X|.M}}true{{else}}false{{end}}", noError,
+		`{{range .X | .M}}"true"{{else}}"false"{{end}}`},
+	{"range []int", "{{range .SI}}{{.}}{{end}}", noError,
+		`{{range .SI}}{{.}}{{end}}`},
+	{"range 1 var", "{{range $x := .SI}}{{.}}{{end}}", noError,
+		`{{range $x := .SI}}{{.}}{{end}}`},
+	{"range 2 vars", "{{range $x, $y := .SI}}{{.}}{{end}}", noError,
+		`{{range $x, $y := .SI}}{{.}}{{end}}`},
+	{"constants", "{{range .SI 1 -3.2i true false 'a' nil}}{{end}}", noError,
+		`{{range .SI 1 -3.2i true false 'a' nil}}{{end}}`},
+	{"template", "{{template `x`}}", noError,
+		`{{template "x"}}`},
+	{"template with arg", "{{template `x` .Y}}", noError,
+		`{{template "x" .Y}}`},
+	{"with", "{{with .X}}hello{{end}}", noError,
+		`{{with .X}}"hello"{{end}}`},
+	{"with with else", "{{with .X}}hello{{else}}goodbye{{end}}", noError,
+		`{{with .X}}"hello"{{else}}"goodbye"{{end}}`},
+	// Errors.
+	{"unclosed action", "hello{{range", hasError, ""},
+	{"unmatched end", "{{end}}", hasError, ""},
+	{"missing end", "hello{{range .x}}", hasError, ""},
+	{"missing end after else", "hello{{range .x}}{{else}}", hasError, ""},
+	{"undefined function", "hello{{undefined}}", hasError, ""},
+	{"undefined variable", "{{$x}}", hasError, ""},
+	{"variable undefined after end", "{{with $x := 4}}{{end}}{{$x}}", hasError, ""},
+	{"variable undefined in template", "{{template $v}}", hasError, ""},
+	{"declare with field", "{{with $x.Y := 4}}{{end}}", hasError, ""},
+	{"template with field ref", "{{template .X}}", hasError, ""},
+	{"template with var", "{{template $v}}", hasError, ""},
+	{"invalid punctuation", "{{printf 3, 4}}", hasError, ""},
+	{"multidecl outside range", "{{with $v, $u := 3}}{{end}}", hasError, ""},
+	{"too many decls in range", "{{range $u, $v, $w := 3}}{{end}}", hasError, ""},
+	{"dot applied to parentheses", "{{printf (printf .).}}", hasError, ""},
+	{"adjacent args", "{{printf 3`x`}}", hasError, ""},
+	{"adjacent args with .", "{{printf `x`.}}", hasError, ""},
+	{"extra end after if", "{{if .X}}a{{else if .Y}}b{{end}}{{end}}", hasError, ""},
+	// Equals (and other chars) do not assignments make (yet).
+	{"bug0a", "{{$x := 0}}{{$x}}", noError, "{{$x := 0}}{{$x}}"},
+	{"bug0b", "{{$x = 1}}{{$x}}", hasError, ""},
+	{"bug0c", "{{$x ! 2}}{{$x}}", hasError, ""},
+	{"bug0d", "{{$x % 3}}{{$x}}", hasError, ""},
+	// Check the parse fails for := rather than comma.
+	{"bug0e", "{{range $x := $y := 3}}{{end}}", hasError, ""},
+	// Another bug: variable read must ignore following punctuation.
+	{"bug1a", "{{$x:=.}}{{$x!2}}", hasError, ""},                     // ! is just illegal here.
+	{"bug1b", "{{$x:=.}}{{$x+2}}", hasError, ""},                     // $x+2 should not parse as ($x) (+2).
+	{"bug1c", "{{$x:=.}}{{$x +2}}", noError, "{{$x := .}}{{$x +2}}"}, // It's OK with a space.
+}
+
+var builtins = map[string]interface{}{
+	"printf": fmt.Sprintf,
+}
+
+func testParse(doCopy bool, t *testing.T) {
+	textFormat = "%q"
+	defer func() { textFormat = "%s" }()
+	for _, test := range parseTests {
+		tmpl, err := New(test.name).Parse(test.input, "", "", make(map[string]*Tree), builtins)
+		switch {
+		case err == nil && !test.ok:
+			t.Errorf("%q: expected error; got none", test.name)
+			continue
+		case err != nil && test.ok:
+			t.Errorf("%q: unexpected error: %v", test.name, err)
+			continue
+		case err != nil && !test.ok:
+			// expected error, got one
+			if *debug {
+				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
+			}
+			continue
+		}
+		var result string
+		if doCopy {
+			result = tmpl.Root.Copy().String()
+		} else {
+			result = tmpl.Root.String()
+		}
+		if result != test.result {
+			t.Errorf("%s=(%q): got\n\t%v\nexpected\n\t%v", test.name, test.input, result, test.result)
+		}
+	}
+}
+
+func TestParse(t *testing.T) {
+	testParse(false, t)
+}
+
+// Same as TestParse, but we copy the node first
+func TestParseCopy(t *testing.T) {
+	testParse(true, t)
+}
+
+type isEmptyTest struct {
+	name  string
+	input string
+	empty bool
+}
+
+var isEmptyTests = []isEmptyTest{
+	{"empty", ``, true},
+	{"nonempty", `hello`, false},
+	{"spaces only", " \t\n \t\n", true},
+	{"definition", `{{define "x"}}something{{end}}`, true},
+	{"definitions and space", "{{define `x`}}something{{end}}\n\n{{define `y`}}something{{end}}\n\n", true},
+	{"definitions and text", "{{define `x`}}something{{end}}\nx\n{{define `y`}}something{{end}}\ny\n", false},
+	{"definition and action", "{{define `x`}}something{{end}}{{if 3}}foo{{end}}", false},
+}
+
+func TestIsEmpty(t *testing.T) {
+	if !IsEmptyTree(nil) {
+		t.Errorf("nil tree is not empty")
+	}
+	for _, test := range isEmptyTests {
+		tree, err := New("root").Parse(test.input, "", "", make(map[string]*Tree), nil)
+		if err != nil {
+			t.Errorf("%q: unexpected error: %v", test.name, err)
+			continue
+		}
+		if empty := IsEmptyTree(tree.Root); empty != test.empty {
+			t.Errorf("%q: expected %t got %t", test.name, test.empty, empty)
+		}
+	}
+}
+
+func TestErrorContextWithTreeCopy(t *testing.T) {
+	tree, err := New("root").Parse("{{if true}}{{end}}", "", "", make(map[string]*Tree), nil)
+	if err != nil {
+		t.Fatalf("unexpected tree parse failure: %v", err)
+	}
+	treeCopy := tree.Copy()
+	wantLocation, wantContext := tree.ErrorContext(tree.Root.Nodes[0])
+	gotLocation, gotContext := treeCopy.ErrorContext(treeCopy.Root.Nodes[0])
+	if wantLocation != gotLocation {
+		t.Errorf("wrong error location want %q got %q", wantLocation, gotLocation)
+	}
+	if wantContext != gotContext {
+		t.Errorf("wrong error location want %q got %q", wantContext, gotContext)
+	}
+}
+
+// All failures, and the result is a string that must appear in the error message.
+var errorTests = []parseTest{
+	// Check line numbers are accurate.
+	{"unclosed1",
+		"line1\n{{",
+		hasError, `unclosed1:2: unexpected unclosed action in command`},
+	{"unclosed2",
+		"line1\n{{define `x`}}line2\n{{",
+		hasError, `unclosed2:3: unexpected unclosed action in command`},
+	// Specific errors.
+	{"function",
+		"{{foo}}",
+		hasError, `function "foo" not defined`},
+	{"comment",
+		"{{/*}}",
+		hasError, `unclosed comment`},
+	{"lparen",
+		"{{.X (1 2 3}}",
+		hasError, `unclosed left paren`},
+	{"rparen",
+		"{{.X 1 2 3)}}",
+		hasError, `unexpected ")"`},
+	{"space",
+		"{{`x`3}}",
+		hasError, `missing space?`},
+	{"idchar",
+		"{{a#}}",
+		hasError, `'#'`},
+	{"charconst",
+		"{{'a}}",
+		hasError, `unterminated character constant`},
+	{"stringconst",
+		`{{"a}}`,
+		hasError, `unterminated quoted string`},
+	{"rawstringconst",
+		"{{`a}}",
+		hasError, `unterminated raw quoted string`},
+	{"number",
+		"{{0xi}}",
+		hasError, `number syntax`},
+	{"multidefine",
+		"{{define `a`}}a{{end}}{{define `a`}}b{{end}}",
+		hasError, `multiple definition of template`},
+	{"eof",
+		"{{range .X}}",
+		hasError, `unexpected EOF`},
+	{"variable",
+		// Declare $x so it's defined, to avoid that error, and then check we don't parse a declaration.
+		"{{$x := 23}}{{with $x.y := 3}}{{$x 23}}{{end}}",
+		hasError, `unexpected ":="`},
+	{"multidecl",
+		"{{$a,$b,$c := 23}}",
+		hasError, `too many declarations`},
+	{"undefvar",
+		"{{$a}}",
+		hasError, `undefined variable`},
+}
+
+func TestErrors(t *testing.T) {
+	for _, test := range errorTests {
+		_, err := New(test.name).Parse(test.input, "", "", make(map[string]*Tree))
+		if err == nil {
+			t.Errorf("%q: expected error", test.name)
+			continue
+		}
+		if !strings.Contains(err.Error(), test.result) {
+			t.Errorf("%q: error %q does not contain %q", test.name, err, test.result)
+		}
+	}
+}
diff --git a/src/text/template/template.go b/src/text/template/template.go
new file mode 100644
index 000000000..249d0cbfb
--- /dev/null
+++ b/src/text/template/template.go
@@ -0,0 +1,217 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package template
+
+import (
+	"fmt"
+	"reflect"
+	"text/template/parse"
+)
+
+// common holds the information shared by related templates.
+type common struct {
+	tmpl map[string]*Template
+	// We use two maps, one for parsing and one for execution.
+	// This separation makes the API cleaner since it doesn't
+	// expose reflection to the client.
+	parseFuncs FuncMap
+	execFuncs  map[string]reflect.Value
+}
+
+// Template is the representation of a parsed template. The *parse.Tree
+// field is exported only for use by html/template and should be treated
+// as unexported by all other clients.
+type Template struct {
+	name string
+	*parse.Tree
+	*common
+	leftDelim  string
+	rightDelim string
+}
+
+// New allocates a new template with the given name.
+func New(name string) *Template {
+	return &Template{
+		name: name,
+	}
+}
+
+// Name returns the name of the template.
+func (t *Template) Name() string {
+	return t.name
+}
+
+// New allocates a new template associated with the given one and with the same
+// delimiters. The association, which is transitive, allows one template to
+// invoke another with a {{template}} action.
+func (t *Template) New(name string) *Template {
+	t.init()
+	return &Template{
+		name:       name,
+		common:     t.common,
+		leftDelim:  t.leftDelim,
+		rightDelim: t.rightDelim,
+	}
+}
+
+func (t *Template) init() {
+	if t.common == nil {
+		t.common = new(common)
+		t.tmpl = make(map[string]*Template)
+		t.parseFuncs = make(FuncMap)
+		t.execFuncs = make(map[string]reflect.Value)
+	}
+}
+
+// Clone returns a duplicate of the template, including all associated
+// templates. The actual representation is not copied, but the name space of
+// associated templates is, so further calls to Parse in the copy will add
+// templates to the copy but not to the original. Clone can be used to prepare
+// common templates and use them with variant definitions for other templates
+// by adding the variants after the clone is made.
+func (t *Template) Clone() (*Template, error) {
+	nt := t.copy(nil)
+	nt.init()
+	nt.tmpl[t.name] = nt
+	for k, v := range t.tmpl {
+		if k == t.name { // Already installed.
+			continue
+		}
+		// The associated templates share nt's common structure.
+		tmpl := v.copy(nt.common)
+		nt.tmpl[k] = tmpl
+	}
+	for k, v := range t.parseFuncs {
+		nt.parseFuncs[k] = v
+	}
+	for k, v := range t.execFuncs {
+		nt.execFuncs[k] = v
+	}
+	return nt, nil
+}
+
+// copy returns a shallow copy of t, with common set to the argument.
+func (t *Template) copy(c *common) *Template {
+	nt := New(t.name)
+	nt.Tree = t.Tree
+	nt.common = c
+	nt.leftDelim = t.leftDelim
+	nt.rightDelim = t.rightDelim
+	return nt
+}
+
+// AddParseTree creates a new template with the name and parse tree
+// and associates it with t.
+func (t *Template) AddParseTree(name string, tree *parse.Tree) (*Template, error) {
+	if t.common != nil && t.tmpl[name] != nil {
+		return nil, fmt.Errorf("template: redefinition of template %q", name)
+	}
+	nt := t.New(name)
+	nt.Tree = tree
+	t.tmpl[name] = nt
+	return nt, nil
+}
+
+// Templates returns a slice of the templates associated with t, including t
+// itself.
+func (t *Template) Templates() []*Template {
+	if t.common == nil {
+		return nil
+	}
+	// Return a slice so we don't expose the map.
+	m := make([]*Template, 0, len(t.tmpl))
+	for _, v := range t.tmpl {
+		m = append(m, v)
+	}
+	return m
+}
+
+// Delims sets the action delimiters to the specified strings, to be used in
+// subsequent calls to Parse, ParseFiles, or ParseGlob. Nested template
+// definitions will inherit the settings. An empty delimiter stands for the
+// corresponding default: {{ or }}.
+// The return value is the template, so calls can be chained.
+func (t *Template) Delims(left, right string) *Template {
+	t.leftDelim = left
+	t.rightDelim = right
+	return t
+}
+
+// Funcs adds the elements of the argument map to the template's function map.
+// It panics if a value in the map is not a function with appropriate return
+// type. However, it is legal to overwrite elements of the map. The return
+// value is the template, so calls can be chained.
+func (t *Template) Funcs(funcMap FuncMap) *Template {
+	t.init()
+	addValueFuncs(t.execFuncs, funcMap)
+	addFuncs(t.parseFuncs, funcMap)
+	return t
+}
+
+// Lookup returns the template with the given name that is associated with t,
+// or nil if there is no such template.
+func (t *Template) Lookup(name string) *Template {
+	if t.common == nil {
+		return nil
+	}
+	return t.tmpl[name]
+}
+
+// Parse parses a string into a template. Nested template definitions will be
+// associated with the top-level template t. Parse may be called multiple times
+// to parse definitions of templates to associate with t. It is an error if a
+// resulting template is non-empty (contains content other than template
+// definitions) and would replace a non-empty template with the same name.
+// (In multiple calls to Parse with the same receiver template, only one call
+// can contain text other than space, comments, and template definitions.)
+func (t *Template) Parse(text string) (*Template, error) {
+	t.init()
+	trees, err := parse.Parse(t.name, text, t.leftDelim, t.rightDelim, t.parseFuncs, builtins)
+	if err != nil {
+		return nil, err
+	}
+	// Add the newly parsed trees, including the one for t, into our common structure.
+	for name, tree := range trees {
+		// If the name we parsed is the name of this template, overwrite this template.
+		// The associate method checks it's not a redefinition.
+		tmpl := t
+		if name != t.name {
+			tmpl = t.New(name)
+		}
+		// Even if t == tmpl, we need to install it in the common.tmpl map.
+		if replace, err := t.associate(tmpl, tree); err != nil {
+			return nil, err
+		} else if replace {
+			tmpl.Tree = tree
+		}
+		tmpl.leftDelim = t.leftDelim
+		tmpl.rightDelim = t.rightDelim
+	}
+	return t, nil
+}
+
+// associate installs the new template into the group of templates associated
+// with t. It is an error to reuse a name except to overwrite an empty
+// template. The two are already known to share the common structure.
+// The boolean return value reports wither to store this tree as t.Tree.
+func (t *Template) associate(new *Template, tree *parse.Tree) (bool, error) {
+	if new.common != t.common {
+		panic("internal error: associate not common")
+	}
+	name := new.name
+	if old := t.tmpl[name]; old != nil {
+		oldIsEmpty := parse.IsEmptyTree(old.Root)
+		newIsEmpty := parse.IsEmptyTree(tree.Root)
+		if newIsEmpty {
+			// Whether old is empty or not, new is empty; no reason to replace old.
+			return false, nil
+		}
+		if !oldIsEmpty {
+			return false, fmt.Errorf("template: redefinition of template %q", name)
+		}
+	}
+	t.tmpl[name] = new
+	return true, nil
+}
diff --git a/src/text/template/testdata/file1.tmpl b/src/text/template/testdata/file1.tmpl
new file mode 100644
index 000000000..febf9d9f8
--- /dev/null
+++ b/src/text/template/testdata/file1.tmpl
@@ -0,0 +1,2 @@
+{{define "x"}}TEXT{{end}}
+{{define "dotV"}}{{.V}}{{end}}
diff --git a/src/text/template/testdata/file2.tmpl b/src/text/template/testdata/file2.tmpl
new file mode 100644
index 000000000..39bf6fb9e
--- /dev/null
+++ b/src/text/template/testdata/file2.tmpl
@@ -0,0 +1,2 @@
+{{define "dot"}}{{.}}{{end}}
+{{define "nested"}}{{template "dot" .}}{{end}}
diff --git a/src/text/template/testdata/tmpl1.tmpl b/src/text/template/testdata/tmpl1.tmpl
new file mode 100644
index 000000000..b72b3a340
--- /dev/null
+++ b/src/text/template/testdata/tmpl1.tmpl
@@ -0,0 +1,3 @@
+template1
+{{define "x"}}x{{end}}
+{{template "y"}}
diff --git a/src/text/template/testdata/tmpl2.tmpl b/src/text/template/testdata/tmpl2.tmpl
new file mode 100644
index 000000000..16beba6e7
--- /dev/null
+++ b/src/text/template/testdata/tmpl2.tmpl
@@ -0,0 +1,3 @@
+template2
+{{define "y"}}y{{end}}
+{{template "x"}}