1 files changed, 358 insertions, 0 deletions
diff --git a/libgo/go/go/types/check.go b/libgo/go/go/types/check.go
new file mode 100644
index 00000000000..bb0b07415e8
--- /dev/null
+++ b/libgo/go/go/types/check.go
@@ -0,0 +1,358 @@
+// 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.
+
+// This file implements the Check function, which drives type-checking.
+
+package types
+
+import (
+	"go/ast"
+	"go/constant"
+	"go/token"
+)
+
+// debugging/development support
+const (
+	debug = false // leave on during development
+	trace = false // turn on for detailed type resolution traces
+)
+
+// If Strict is set, the type-checker enforces additional
+// rules not specified by the Go 1 spec, but which will
+// catch guaranteed run-time errors if the respective
+// code is executed. In other words, programs passing in
+// Strict mode are Go 1 compliant, but not all Go 1 programs
+// will pass in Strict mode. The additional rules are:
+//
+// - A type assertion x.(T) where T is an interface type
+//   is invalid if any (statically known) method that exists
+//   for both x and T have different signatures.
+//
+const strict = false
+
+// exprInfo stores information about an untyped expression.
+type exprInfo struct {
+	isLhs bool // expression is lhs operand of a shift with delayed type-check
+	mode  operandMode
+	typ   *Basic
+	val   constant.Value // constant value; or nil (if not a constant)
+}
+
+// funcInfo stores the information required for type-checking a function.
+type funcInfo struct {
+	name string    // for debugging/tracing only
+	decl *declInfo // for cycle detection
+	sig  *Signature
+	body *ast.BlockStmt
+}
+
+// A context represents the context within which an object is type-checked.
+type context struct {
+	decl          *declInfo      // package-level declaration whose init expression/function body is checked
+	scope         *Scope         // top-most scope for lookups
+	iota          constant.Value // value of iota in a constant declaration; nil otherwise
+	sig           *Signature     // function signature if inside a function; nil otherwise
+	hasLabel      bool           // set if a function makes use of labels (only ~1% of functions); unused outside functions
+	hasCallOrRecv bool           // set if an expression contains a function call or channel receive operation
+}
+
+// A Checker maintains the state of the type checker.
+// It must be created with NewChecker.
+type Checker struct {
+	// package information
+	// (initialized by NewChecker, valid for the life-time of checker)
+	conf *Config
+	fset *token.FileSet
+	pkg  *Package
+	*Info
+	objMap map[Object]*declInfo // maps package-level object to declaration info
+
+	// information collected during type-checking of a set of package files
+	// (initialized by Files, valid only for the duration of check.Files;
+	// maps and lists are allocated on demand)
+	files            []*ast.File                       // package files
+	unusedDotImports map[*Scope]map[*Package]token.Pos // positions of unused dot-imported packages for each file scope
+
+	firstErr error                 // first error encountered
+	methods  map[string][]*Func    // maps type names to associated methods
+	untyped  map[ast.Expr]exprInfo // map of expressions without final type
+	funcs    []funcInfo            // list of functions to type-check
+	delayed  []func()              // delayed checks requiring fully setup types
+
+	// context within which the current object is type-checked
+	// (valid only for the duration of type-checking a specific object)
+	context
+	pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
+
+	// debugging
+	indent int // indentation for tracing
+}
+
+// addUnusedImport adds the position of a dot-imported package
+// pkg to the map of dot imports for the given file scope.
+func (check *Checker) addUnusedDotImport(scope *Scope, pkg *Package, pos token.Pos) {
+	mm := check.unusedDotImports
+	if mm == nil {
+		mm = make(map[*Scope]map[*Package]token.Pos)
+		check.unusedDotImports = mm
+	}
+	m := mm[scope]
+	if m == nil {
+		m = make(map[*Package]token.Pos)
+		mm[scope] = m
+	}
+	m[pkg] = pos
+}
+
+// addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
+func (check *Checker) addDeclDep(to Object) {
+	from := check.decl
+	if from == nil {
+		return // not in a package-level init expression
+	}
+	if _, found := check.objMap[to]; !found {
+		return // to is not a package-level object
+	}
+	from.addDep(to)
+}
+
+func (check *Checker) assocMethod(tname string, meth *Func) {
+	m := check.methods
+	if m == nil {
+		m = make(map[string][]*Func)
+		check.methods = m
+	}
+	m[tname] = append(m[tname], meth)
+}
+
+func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
+	m := check.untyped
+	if m == nil {
+		m = make(map[ast.Expr]exprInfo)
+		check.untyped = m
+	}
+	m[e] = exprInfo{lhs, mode, typ, val}
+}
+
+func (check *Checker) later(name string, decl *declInfo, sig *Signature, body *ast.BlockStmt) {
+	check.funcs = append(check.funcs, funcInfo{name, decl, sig, body})
+}
+
+func (check *Checker) delay(f func()) {
+	check.delayed = append(check.delayed, f)
+}
+
+// NewChecker returns a new Checker instance for a given package.
+// Package files may be added incrementally via checker.Files.
+func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
+	// make sure we have a configuration
+	if conf == nil {
+		conf = new(Config)
+	}
+
+	// make sure we have an info struct
+	if info == nil {
+		info = new(Info)
+	}
+
+	return &Checker{
+		conf:   conf,
+		fset:   fset,
+		pkg:    pkg,
+		Info:   info,
+		objMap: make(map[Object]*declInfo),
+	}
+}
+
+// initFiles initializes the files-specific portion of checker.
+// The provided files must all belong to the same package.
+func (check *Checker) initFiles(files []*ast.File) {
+	// start with a clean slate (check.Files may be called multiple times)
+	check.files = nil
+	check.unusedDotImports = nil
+
+	check.firstErr = nil
+	check.methods = nil
+	check.untyped = nil
+	check.funcs = nil
+	check.delayed = nil
+
+	// determine package name and collect valid files
+	pkg := check.pkg
+	for _, file := range files {
+		switch name := file.Name.Name; pkg.name {
+		case "":
+			if name != "_" {
+				pkg.name = name
+			} else {
+				check.errorf(file.Name.Pos(), "invalid package name _")
+			}
+			fallthrough
+
+		case name:
+			check.files = append(check.files, file)
+
+		default:
+			check.errorf(file.Package, "package %s; expected %s", name, pkg.name)
+			// ignore this file
+		}
+	}
+}
+
+// A bailout panic is used for early termination.
+type bailout struct{}
+
+func (check *Checker) handleBailout(err *error) {
+	switch p := recover().(type) {
+	case nil, bailout:
+		// normal return or early exit
+		*err = check.firstErr
+	default:
+		// re-panic
+		panic(p)
+	}
+}
+
+// Files checks the provided files as part of the checker's package.
+func (check *Checker) Files(files []*ast.File) (err error) {
+	defer check.handleBailout(&err)
+
+	check.initFiles(files)
+
+	check.collectObjects()
+
+	check.packageObjects(check.resolveOrder())
+
+	check.functionBodies()
+
+	check.initOrder()
+
+	if !check.conf.DisableUnusedImportCheck {
+		check.unusedImports()
+	}
+
+	// perform delayed checks
+	for _, f := range check.delayed {
+		f()
+	}
+
+	check.recordUntyped()
+
+	check.pkg.complete = true
+	return
+}
+
+func (check *Checker) recordUntyped() {
+	if !debug && check.Types == nil {
+		return // nothing to do
+	}
+
+	for x, info := range check.untyped {
+		if debug && isTyped(info.typ) {
+			check.dump("%s: %s (type %s) is typed", x.Pos(), x, info.typ)
+			unreachable()
+		}
+		check.recordTypeAndValue(x, info.mode, info.typ, info.val)
+	}
+}
+
+func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
+	assert(x != nil)
+	assert(typ != nil)
+	if mode == invalid {
+		return // omit
+	}
+	assert(typ != nil)
+	if mode == constant_ {
+		assert(val != nil)
+		assert(typ == Typ[Invalid] || isConstType(typ))
+	}
+	if m := check.Types; m != nil {
+		m[x] = TypeAndValue{mode, typ, val}
+	}
+}
+
+func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
+	// f must be a (possibly parenthesized) identifier denoting a built-in
+	// (built-ins in package unsafe always produce a constant result and
+	// we don't record their signatures, so we don't see qualified idents
+	// here): record the signature for f and possible children.
+	for {
+		check.recordTypeAndValue(f, builtin, sig, nil)
+		switch p := f.(type) {
+		case *ast.Ident:
+			return // we're done
+		case *ast.ParenExpr:
+			f = p.X
+		default:
+			unreachable()
+		}
+	}
+}
+
+func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
+	assert(x != nil)
+	if a[0] == nil || a[1] == nil {
+		return
+	}
+	assert(isTyped(a[0]) && isTyped(a[1]) && isBoolean(a[1]))
+	if m := check.Types; m != nil {
+		for {
+			tv := m[x]
+			assert(tv.Type != nil) // should have been recorded already
+			pos := x.Pos()
+			tv.Type = NewTuple(
+				NewVar(pos, check.pkg, "", a[0]),
+				NewVar(pos, check.pkg, "", a[1]),
+			)
+			m[x] = tv
+			// if x is a parenthesized expression (p.X), update p.X
+			p, _ := x.(*ast.ParenExpr)
+			if p == nil {
+				break
+			}
+			x = p.X
+		}
+	}
+}
+
+func (check *Checker) recordDef(id *ast.Ident, obj Object) {
+	assert(id != nil)
+	if m := check.Defs; m != nil {
+		m[id] = obj
+	}
+}
+
+func (check *Checker) recordUse(id *ast.Ident, obj Object) {
+	assert(id != nil)
+	assert(obj != nil)
+	if m := check.Uses; m != nil {
+		m[id] = obj
+	}
+}
+
+func (check *Checker) recordImplicit(node ast.Node, obj Object) {
+	assert(node != nil)
+	assert(obj != nil)
+	if m := check.Implicits; m != nil {
+		m[node] = obj
+	}
+}
+
+func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
+	assert(obj != nil && (recv == nil || len(index) > 0))
+	check.recordUse(x.Sel, obj)
+	// TODO(gri) Should we also call recordTypeAndValue?
+	if m := check.Selections; m != nil {
+		m[x] = &Selection{kind, recv, obj, index, indirect}
+	}
+}
+
+func (check *Checker) recordScope(node ast.Node, scope *Scope) {
+	assert(node != nil)
+	assert(scope != nil)
+	if m := check.Scopes; m != nil {
+		m[node] = scope
+	}
+}