fmt: make the %#v verb a special flag

The %#v verb is special: it says all values below need to print as %#v.
However, for some situations the # flag has other meanings and this
causes some issues, particularly in how Formatters work. Since %#v
dominates all formatting, translate it into actual state of the formatter
and decouple it from the # flag itself within the calculations (although
it must be restored when methods are doing the work.)
The result is cleaner code and correct handling of # for Formatters.
TODO: Apply the same thinking to the + flag in a followup CL.

Also, the wasString return value in handleMethods is always false,
so eliminate it.

Update issue 8835

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://codereview.appspot.com/146650043

3 files changed, 196 insertions, 84 deletions

diff --git a/src/fmt/fmt_test.go b/src/fmt/fmt_test.go
index 4586fcf93..f3b527d1f 100644
--- a/src/fmt/fmt_test.go
+++ b/src/fmt/fmt_test.go
@@ -1144,10 +1144,10 @@ var panictests = []struct {
 }
 
 func TestPanics(t *testing.T) {
-	for _, tt := range panictests {
+	for i, tt := range panictests {
 		s := Sprintf(tt.fmt, tt.in)
 		if s != tt.out {
-			t.Errorf("%q: got %q expected %q", tt.fmt, s, tt.out)
+			t.Errorf("%d: %q: got %q expected %q", i, tt.fmt, s, tt.out)
 		}
 	}
 }
@@ -1207,3 +1207,94 @@ func TestNilDoesNotBecomeTyped(t *testing.T) {
 		t.Errorf("expected:\n\t%q\ngot:\n\t%q", expect, got)
 	}
 }
+
+// Formatters did not get delivered flags correctly in all cases. Issue 8835.
+type fp struct{}
+
+func (fp) Format(f State, c rune) {
+	s := "%"
+	for i := 0; i < 128; i++ {
+		if f.Flag(i) {
+			s += string(i)
+		}
+	}
+	if w, ok := f.Width(); ok {
+		s += Sprintf("%d", w)
+	}
+	if p, ok := f.Precision(); ok {
+		s += Sprintf(".%d", p)
+	}
+	s += string(c)
+	io.WriteString(f, "["+s+"]")
+}
+
+var formatterFlagTests = []struct {
+	in  string
+	val interface{}
+	out string
+}{
+	// scalar values with the (unused by fmt) 'a' verb.
+	{"%a", fp{}, "[%a]"},
+	{"%-a", fp{}, "[%-a]"},
+	{"%+a", fp{}, "[%+a]"},
+	{"%#a", fp{}, "[%#a]"},
+	{"% a", fp{}, "[% a]"},
+	{"%0a", fp{}, "[%0a]"},
+	{"%1.2a", fp{}, "[%1.2a]"},
+	{"%-1.2a", fp{}, "[%-1.2a]"},
+	{"%+1.2a", fp{}, "[%+1.2a]"},
+	{"%-+1.2a", fp{}, "[%+-1.2a]"},
+	{"%-+1.2abc", fp{}, "[%+-1.2a]bc"},
+	{"%-1.2abc", fp{}, "[%-1.2a]bc"},
+
+	// composite values with the 'a' verb
+	{"%a", [1]fp{}, "[[%a]]"},
+	{"%-a", [1]fp{}, "[[%-a]]"},
+	{"%+a", [1]fp{}, "[[%+a]]"},
+	{"%#a", [1]fp{}, "[[%#a]]"},
+	{"% a", [1]fp{}, "[[% a]]"},
+	{"%0a", [1]fp{}, "[[%0a]]"},
+	{"%1.2a", [1]fp{}, "[[%1.2a]]"},
+	{"%-1.2a", [1]fp{}, "[[%-1.2a]]"},
+	{"%+1.2a", [1]fp{}, "[[%+1.2a]]"},
+	{"%-+1.2a", [1]fp{}, "[[%+-1.2a]]"},
+	{"%-+1.2abc", [1]fp{}, "[[%+-1.2a]]bc"},
+	{"%-1.2abc", [1]fp{}, "[[%-1.2a]]bc"},
+
+	// simple values with the 'v' verb
+	{"%v", fp{}, "[%v]"},
+	{"%-v", fp{}, "[%-v]"},
+	{"%+v", fp{}, "[%+v]"},
+	{"%#v", fp{}, "[%#v]"},
+	{"% v", fp{}, "[% v]"},
+	{"%0v", fp{}, "[%0v]"},
+	{"%1.2v", fp{}, "[%1.2v]"},
+	{"%-1.2v", fp{}, "[%-1.2v]"},
+	{"%+1.2v", fp{}, "[%+1.2v]"},
+	{"%-+1.2v", fp{}, "[%+-1.2v]"},
+	{"%-+1.2vbc", fp{}, "[%+-1.2v]bc"},
+	{"%-1.2vbc", fp{}, "[%-1.2v]bc"},
+
+	// composite values with the 'v' verb. Some are still broken.
+	{"%v", [1]fp{}, "[[%v]]"},
+	{"%-v", [1]fp{}, "[[%-v]]"},
+	//{"%+v", [1]fp{}, "[[%+v]]"},
+	{"%#v", [1]fp{}, "[1]fmt_test.fp{[%#v]}"},
+	{"% v", [1]fp{}, "[[% v]]"},
+	{"%0v", [1]fp{}, "[[%0v]]"},
+	{"%1.2v", [1]fp{}, "[[%1.2v]]"},
+	{"%-1.2v", [1]fp{}, "[[%-1.2v]]"},
+	//{"%+1.2v", [1]fp{}, "[[%+1.2v]]"},
+	//{"%-+1.2v", [1]fp{}, "[[%+-1.2v]]"},
+	//{"%-+1.2vbc", [1]fp{}, "[[%+-1.2v]]bc"},
+	{"%-1.2vbc", [1]fp{}, "[[%-1.2v]]bc"},
+}
+
+func TestFormatterFlags(t *testing.T) {
+	for _, tt := range formatterFlagTests {
+		s := Sprintf(tt.in, tt.val)
+		if s != tt.out {
+			t.Errorf("Sprintf(%q, %T) = %q, want %q", tt.in, tt.val, s, tt.out)
+		}
+	}
+}
diff --git a/src/fmt/format.go b/src/fmt/format.go
index a92f3c2f8..355b73262 100644
--- a/src/fmt/format.go
+++ b/src/fmt/format.go
@@ -49,9 +49,14 @@ type fmt struct {
 	plus        bool
 	sharp       bool
 	space       bool
-	unicode     bool
-	uniQuote    bool // Use 'x'= prefix for %U if printable.
-	zero        bool
+	// For the format %#v, we set this flag and
+	// clear the plus flag, since it is in effect
+	// a different, flagless format set at the top level.
+	// TODO: plusV could use this too.
+	sharpV   bool
+	unicode  bool
+	uniQuote bool // Use 'x'= prefix for %U if printable.
+	zero     bool
 }
 
 func (f *fmt) clearflags() {
@@ -63,6 +68,7 @@ func (f *fmt) clearflags() {
 	f.plus = false
 	f.sharp = false
 	f.space = false
+	f.sharpV = false
 	f.unicode = false
 	f.uniQuote = false
 	f.zero = false
diff --git a/src/fmt/print.go b/src/fmt/print.go
index de69e90fb..f141d39da 100644
--- a/src/fmt/print.go
+++ b/src/fmt/print.go
@@ -317,11 +317,11 @@ func (p *pp) badVerb(verb rune) {
 	case p.arg != nil:
 		p.buf.WriteString(reflect.TypeOf(p.arg).String())
 		p.add('=')
-		p.printArg(p.arg, 'v', false, false, 0)
+		p.printArg(p.arg, 'v', false, 0)
 	case p.value.IsValid():
 		p.buf.WriteString(p.value.Type().String())
 		p.add('=')
-		p.printValue(p.value, 'v', false, false, 0)
+		p.printValue(p.value, 'v', false, 0)
 	default:
 		p.buf.Write(nilAngleBytes)
 	}
@@ -406,7 +406,7 @@ func (p *pp) fmtUnicode(v int64) {
 	p.fmt.sharp = sharp
 }
 
-func (p *pp) fmtUint64(v uint64, verb rune, goSyntax bool) {
+func (p *pp) fmtUint64(v uint64, verb rune) {
 	switch verb {
 	case 'b':
 		p.fmt.integer(int64(v), 2, unsigned, ldigits)
@@ -415,7 +415,7 @@ func (p *pp) fmtUint64(v uint64, verb rune, goSyntax bool) {
 	case 'd':
 		p.fmt.integer(int64(v), 10, unsigned, ldigits)
 	case 'v':
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.fmt0x64(v, true)
 		} else {
 			p.fmt.integer(int64(v), 10, unsigned, ldigits)
@@ -499,10 +499,10 @@ func (p *pp) fmtComplex128(v complex128, verb rune) {
 	}
 }
 
-func (p *pp) fmtString(v string, verb rune, goSyntax bool) {
+func (p *pp) fmtString(v string, verb rune) {
 	switch verb {
 	case 'v':
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.fmt.fmt_q(v)
 		} else {
 			p.fmt.fmt_s(v)
@@ -520,9 +520,9 @@ func (p *pp) fmtString(v string, verb rune, goSyntax bool) {
 	}
 }
 
-func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, typ reflect.Type, depth int) {
+func (p *pp) fmtBytes(v []byte, verb rune, typ reflect.Type, depth int) {
 	if verb == 'v' || verb == 'd' {
-		if goSyntax {
+		if p.fmt.sharpV {
 			if v == nil {
 				if typ == nil {
 					p.buf.WriteString("[]byte(nil)")
@@ -543,15 +543,15 @@ func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, typ reflect.Type, dept
 		}
 		for i, c := range v {
 			if i > 0 {
-				if goSyntax {
+				if p.fmt.sharpV {
 					p.buf.Write(commaSpaceBytes)
 				} else {
 					p.buf.WriteByte(' ')
 				}
 			}
-			p.printArg(c, 'v', p.fmt.plus, goSyntax, depth+1)
+			p.printArg(c, 'v', p.fmt.plus, depth+1)
 		}
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteByte('}')
 		} else {
 			p.buf.WriteByte(']')
@@ -572,7 +572,7 @@ func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, typ reflect.Type, dept
 	}
 }
 
-func (p *pp) fmtPointer(value reflect.Value, verb rune, goSyntax bool) {
+func (p *pp) fmtPointer(value reflect.Value, verb rune) {
 	use0x64 := true
 	switch verb {
 	case 'p', 'v':
@@ -594,7 +594,7 @@ func (p *pp) fmtPointer(value reflect.Value, verb rune, goSyntax bool) {
 		return
 	}
 
-	if goSyntax {
+	if p.fmt.sharpV {
 		p.add('(')
 		p.buf.WriteString(value.Type().String())
 		p.add(')')
@@ -611,7 +611,7 @@ func (p *pp) fmtPointer(value reflect.Value, verb rune, goSyntax bool) {
 		if use0x64 {
 			p.fmt0x64(uint64(u), !p.fmt.sharp)
 		} else {
-			p.fmtUint64(uint64(u), verb, false)
+			p.fmtUint64(uint64(u), verb)
 		}
 	}
 }
@@ -636,24 +636,44 @@ func (p *pp) catchPanic(arg interface{}, verb rune) {
 			// Nested panics; the recursion in printArg cannot succeed.
 			panic(err)
 		}
+		p.fmt.clearflags() // We are done, and for this output we want default behavior.
 		p.buf.Write(percentBangBytes)
 		p.add(verb)
 		p.buf.Write(panicBytes)
 		p.panicking = true
-		p.printArg(err, 'v', false, false, 0)
+		p.printArg(err, 'v', false, 0)
 		p.panicking = false
 		p.buf.WriteByte(')')
 	}
 }
 
-func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString, handled bool) {
+// clearSpecialFlags pushes %#v back into the regular flags and returns their old state.
+func (p *pp) clearSpecialFlags() bool {
+	ret := p.fmt.sharpV
+	if ret {
+		p.fmt.sharp = true
+		p.fmt.sharpV = false
+	}
+	return ret
+}
+
+// restoreSpecialFlags, whose argument should be a call to clearSpecialFlags,
+// restores the setting of the sharpV flag.
+func (p *pp) restoreSpecialFlags(sharpV bool) {
+	if sharpV {
+		p.fmt.sharp = false
+		p.fmt.sharpV = true
+	}
+}
+
+func (p *pp) handleMethods(verb rune, plus bool, depth int) (handled bool) {
 	if p.erroring {
 		return
 	}
 	// Is it a Formatter?
 	if formatter, ok := p.arg.(Formatter); ok {
 		handled = true
-		wasString = false
+		defer p.restoreSpecialFlags(p.clearSpecialFlags())
 		defer p.catchPanic(p.arg, verb)
 		formatter.Format(p, verb)
 		return
@@ -664,14 +684,13 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
 	}
 
 	// If we're doing Go syntax and the argument knows how to supply it, take care of it now.
-	if goSyntax {
-		p.fmt.sharp = false
+	if p.fmt.sharpV {
 		if stringer, ok := p.arg.(GoStringer); ok {
-			wasString = false
 			handled = true
+			defer p.restoreSpecialFlags(p.clearSpecialFlags())
 			defer p.catchPanic(p.arg, verb)
 			// Print the result of GoString unadorned.
-			p.fmtString(stringer.GoString(), 's', false)
+			p.fmtString(stringer.GoString(), 's')
 			return
 		}
 	} else {
@@ -682,30 +701,27 @@ func (p *pp) handleMethods(verb rune, plus, goSyntax bool, depth int) (wasString
 		case 'v', 's', 'x', 'X', 'q':
 			// Is it an error or Stringer?
 			// The duplication in the bodies is necessary:
-			// setting wasString and handled, and deferring catchPanic,
+			// setting handled and deferring catchPanic
 			// must happen before calling the method.
 			switch v := p.arg.(type) {
 			case error:
-				wasString = false
 				handled = true
 				defer p.catchPanic(p.arg, verb)
-				p.printArg(v.Error(), verb, plus, false, depth)
+				p.printArg(v.Error(), verb, plus, depth)
 				return
 
 			case Stringer:
-				wasString = false
 				handled = true
 				defer p.catchPanic(p.arg, verb)
-				p.printArg(v.String(), verb, plus, false, depth)
+				p.printArg(v.String(), verb, plus, depth)
 				return
 			}
 		}
 	}
-	handled = false
-	return
+	return false
 }
 
-func (p *pp) printArg(arg interface{}, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
+func (p *pp) printArg(arg interface{}, verb rune, plus bool, depth int) (wasString bool) {
 	p.arg = arg
 	p.value = reflect.Value{}
 
@@ -722,10 +738,10 @@ func (p *pp) printArg(arg interface{}, verb rune, plus, goSyntax bool, depth int
 	// %T (the value's type) and %p (its address) are special; we always do them first.
 	switch verb {
 	case 'T':
-		p.printArg(reflect.TypeOf(arg).String(), 's', false, false, 0)
+		p.printArg(reflect.TypeOf(arg).String(), 's', false, 0)
 		return false
 	case 'p':
-		p.fmtPointer(reflect.ValueOf(arg), verb, goSyntax)
+		p.fmtPointer(reflect.ValueOf(arg), verb)
 		return false
 	}
 
@@ -734,13 +750,9 @@ func (p *pp) printArg(arg interface{}, verb rune, plus, goSyntax bool, depth int
 	// We could call handleMethods here and avoid this work, but
 	// handleMethods is expensive enough to be worth delaying.
 	oldPlus := p.fmt.plus
-	oldSharp := p.fmt.sharp
 	if plus {
 		p.fmt.plus = false
 	}
-	if goSyntax {
-		p.fmt.sharp = false
-	}
 
 	// Some types can be done without reflection.
 	switch f := arg.(type) {
@@ -765,40 +777,39 @@ func (p *pp) printArg(arg interface{}, verb rune, plus, goSyntax bool, depth int
 	case int64:
 		p.fmtInt64(f, verb)
 	case uint:
-		p.fmtUint64(uint64(f), verb, goSyntax)
+		p.fmtUint64(uint64(f), verb)
 	case uint8:
-		p.fmtUint64(uint64(f), verb, goSyntax)
+		p.fmtUint64(uint64(f), verb)
 	case uint16:
-		p.fmtUint64(uint64(f), verb, goSyntax)
+		p.fmtUint64(uint64(f), verb)
 	case uint32:
-		p.fmtUint64(uint64(f), verb, goSyntax)
+		p.fmtUint64(uint64(f), verb)
 	case uint64:
-		p.fmtUint64(f, verb, goSyntax)
+		p.fmtUint64(f, verb)
 	case uintptr:
-		p.fmtUint64(uint64(f), verb, goSyntax)
+		p.fmtUint64(uint64(f), verb)
 	case string:
-		p.fmtString(f, verb, goSyntax)
+		p.fmtString(f, verb)
 		wasString = verb == 's' || verb == 'v'
 	case []byte:
-		p.fmtBytes(f, verb, goSyntax, nil, depth)
+		p.fmtBytes(f, verb, nil, depth)
 		wasString = verb == 's'
 	default:
 		// Restore flags in case handleMethods finds a Formatter.
 		p.fmt.plus = oldPlus
-		p.fmt.sharp = oldSharp
 		// If the type is not simple, it might have methods.
-		if isString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
-			return isString
+		if handled := p.handleMethods(verb, plus, depth); handled {
+			return false
 		}
 		// Need to use reflection
-		return p.printReflectValue(reflect.ValueOf(arg), verb, plus, goSyntax, depth)
+		return p.printReflectValue(reflect.ValueOf(arg), verb, plus, depth)
 	}
 	p.arg = nil
 	return
 }
 
 // printValue is like printArg but starts with a reflect value, not an interface{} value.
-func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
+func (p *pp) printValue(value reflect.Value, verb rune, plus bool, depth int) (wasString bool) {
 	if !value.IsValid() {
 		if verb == 'T' || verb == 'v' {
 			p.buf.Write(nilAngleBytes)
@@ -812,10 +823,10 @@ func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, dep
 	// %T (the value's type) and %p (its address) are special; we always do them first.
 	switch verb {
 	case 'T':
-		p.printArg(value.Type().String(), 's', false, false, 0)
+		p.printArg(value.Type().String(), 's', false, 0)
 		return false
 	case 'p':
-		p.fmtPointer(value, verb, goSyntax)
+		p.fmtPointer(value, verb)
 		return false
 	}
 
@@ -825,18 +836,18 @@ func (p *pp) printValue(value reflect.Value, verb rune, plus, goSyntax bool, dep
 	if value.CanInterface() {
 		p.arg = value.Interface()
 	}
-	if isString, handled := p.handleMethods(verb, plus, goSyntax, depth); handled {
-		return isString
+	if handled := p.handleMethods(verb, plus, depth); handled {
+		return false
 	}
 
-	return p.printReflectValue(value, verb, plus, goSyntax, depth)
+	return p.printReflectValue(value, verb, plus, depth)
 }
 
 var byteType = reflect.TypeOf(byte(0))
 
 // printReflectValue is the fallback for both printArg and printValue.
 // It uses reflect to print the value.
-func (p *pp) printReflectValue(value reflect.Value, verb rune, plus, goSyntax bool, depth int) (wasString bool) {
+func (p *pp) printReflectValue(value reflect.Value, verb rune, plus bool, depth int) (wasString bool) {
 	oldValue := p.value
 	p.value = value
 BigSwitch:
@@ -846,7 +857,7 @@ BigSwitch:
 	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 		p.fmtInt64(f.Int(), verb)
 	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		p.fmtUint64(f.Uint(), verb, goSyntax)
+		p.fmtUint64(f.Uint(), verb)
 	case reflect.Float32, reflect.Float64:
 		if f.Type().Size() == 4 {
 			p.fmtFloat32(float32(f.Float()), verb)
@@ -860,9 +871,9 @@ BigSwitch:
 			p.fmtComplex128(f.Complex(), verb)
 		}
 	case reflect.String:
-		p.fmtString(f.String(), verb, goSyntax)
+		p.fmtString(f.String(), verb)
 	case reflect.Map:
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteString(f.Type().String())
 			if f.IsNil() {
 				p.buf.WriteString("(nil)")
@@ -875,23 +886,23 @@ BigSwitch:
 		keys := f.MapKeys()
 		for i, key := range keys {
 			if i > 0 {
-				if goSyntax {
+				if p.fmt.sharpV {
 					p.buf.Write(commaSpaceBytes)
 				} else {
 					p.buf.WriteByte(' ')
 				}
 			}
-			p.printValue(key, verb, plus, goSyntax, depth+1)
+			p.printValue(key, verb, plus, depth+1)
 			p.buf.WriteByte(':')
-			p.printValue(f.MapIndex(key), verb, plus, goSyntax, depth+1)
+			p.printValue(f.MapIndex(key), verb, plus, depth+1)
 		}
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteByte('}')
 		} else {
 			p.buf.WriteByte(']')
 		}
 	case reflect.Struct:
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteString(value.Type().String())
 		}
 		p.add('{')
@@ -899,32 +910,32 @@ BigSwitch:
 		t := v.Type()
 		for i := 0; i < v.NumField(); i++ {
 			if i > 0 {
-				if goSyntax {
+				if p.fmt.sharpV {
 					p.buf.Write(commaSpaceBytes)
 				} else {
 					p.buf.WriteByte(' ')
 				}
 			}
-			if plus || goSyntax {
+			if plus || p.fmt.sharpV {
 				if f := t.Field(i); f.Name != "" {
 					p.buf.WriteString(f.Name)
 					p.buf.WriteByte(':')
 				}
 			}
-			p.printValue(getField(v, i), verb, plus, goSyntax, depth+1)
+			p.printValue(getField(v, i), verb, plus, depth+1)
 		}
 		p.buf.WriteByte('}')
 	case reflect.Interface:
 		value := f.Elem()
 		if !value.IsValid() {
-			if goSyntax {
+			if p.fmt.sharpV {
 				p.buf.WriteString(f.Type().String())
 				p.buf.Write(nilParenBytes)
 			} else {
 				p.buf.Write(nilAngleBytes)
 			}
 		} else {
-			wasString = p.printValue(value, verb, plus, goSyntax, depth+1)
+			wasString = p.printValue(value, verb, plus, depth+1)
 		}
 	case reflect.Array, reflect.Slice:
 		// Byte slices are special:
@@ -947,11 +958,11 @@ BigSwitch:
 					bytes[i] = byte(f.Index(i).Uint())
 				}
 			}
-			p.fmtBytes(bytes, verb, goSyntax, typ, depth)
+			p.fmtBytes(bytes, verb, typ, depth)
 			wasString = verb == 's'
 			break
 		}
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteString(value.Type().String())
 			if f.Kind() == reflect.Slice && f.IsNil() {
 				p.buf.WriteString("(nil)")
@@ -963,15 +974,15 @@ BigSwitch:
 		}
 		for i := 0; i < f.Len(); i++ {
 			if i > 0 {
-				if goSyntax {
+				if p.fmt.sharpV {
 					p.buf.Write(commaSpaceBytes)
 				} else {
 					p.buf.WriteByte(' ')
 				}
 			}
-			p.printValue(f.Index(i), verb, plus, goSyntax, depth+1)
+			p.printValue(f.Index(i), verb, plus, depth+1)
 		}
-		if goSyntax {
+		if p.fmt.sharpV {
 			p.buf.WriteByte('}')
 		} else {
 			p.buf.WriteByte(']')
@@ -984,17 +995,17 @@ BigSwitch:
 			switch a := f.Elem(); a.Kind() {
 			case reflect.Array, reflect.Slice:
 				p.buf.WriteByte('&')
-				p.printValue(a, verb, plus, goSyntax, depth+1)
+				p.printValue(a, verb, plus, depth+1)
 				break BigSwitch
 			case reflect.Struct:
 				p.buf.WriteByte('&')
-				p.printValue(a, verb, plus, goSyntax, depth+1)
+				p.printValue(a, verb, plus, depth+1)
 				break BigSwitch
 			}
 		}
 		fallthrough
 	case reflect.Chan, reflect.Func, reflect.UnsafePointer:
-		p.fmtPointer(value, verb, goSyntax)
+		p.fmtPointer(value, verb)
 	default:
 		p.unknownType(f)
 	}
@@ -1160,9 +1171,13 @@ func (p *pp) doPrintf(format string, a []interface{}) {
 		arg := a[argNum]
 		argNum++
 
-		goSyntax := c == 'v' && p.fmt.sharp
+		if c == 'v' && p.fmt.sharp {
+			// Go syntax. Set the flag in the fmt and clear the sharp flag.
+			p.fmt.sharp = false
+			p.fmt.sharpV = true
+		}
 		plus := c == 'v' && p.fmt.plus
-		p.printArg(arg, c, plus, goSyntax, 0)
+		p.printArg(arg, c, plus, 0)
 	}
 
 	// Check for extra arguments unless the call accessed the arguments
@@ -1176,7 +1191,7 @@ func (p *pp) doPrintf(format string, a []interface{}) {
 				p.buf.WriteString(reflect.TypeOf(arg).String())
 				p.buf.WriteByte('=')
 			}
-			p.printArg(arg, 'v', false, false, 0)
+			p.printArg(arg, 'v', false, 0)
 			if argNum+1 < len(a) {
 				p.buf.Write(commaSpaceBytes)
 			}
@@ -1197,7 +1212,7 @@ func (p *pp) doPrint(a []interface{}, addspace, addnewline bool) {
 				p.buf.WriteByte(' ')
 			}
 		}
-		prevString = p.printArg(arg, 'v', false, false, 0)
+		prevString = p.printArg(arg, 'v', false, 0)
 	}
 	if addnewline {
 		p.buf.WriteByte('\n')