cmd/compile: suppress export of Note field within exported bodies

Added a format option to inhibit output of .Note field in
printing, and enabled that option during export.
Added test.

Fixes #13777.

Change-Id: I739f9785eb040f2fecbeb96d5a9ceb8c1ca0f772
Reviewed-on: https://go-review.googlesource.com/18217Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Chase <drchase@google.com>

src/cmd/compile/internal/gc/export.go

@@ -257,7 +257,7 @@ func dumpexportvar(s *Sym) {
 			}
 
 			// NOTE: The space after %#S here is necessary for ld's export data parser.
-			exportf("\tfunc %v %v { %v }\n", Sconv(s, obj.FmtSharp), Tconv(t, obj.FmtShort|obj.FmtSharp), Hconv(n.Func.Inl, obj.FmtSharp))
+			exportf("\tfunc %v %v { %v }\n", Sconv(s, obj.FmtSharp), Tconv(t, obj.FmtShort|obj.FmtSharp), Hconv(n.Func.Inl, obj.FmtSharp|obj.FmtBody))
 
 			reexportdeplist(n.Func.Inl)
 		} else {

src/cmd/compile/internal/gc/fmt.go

@@ -63,6 +63,8 @@ var fmtmode int = FErr
 
 var fmtpkgpfx int // %uT stickyness
 
+var fmtbody bool
+
 //
 // E.g. for %S:	%+S %#S %-S	print an identifier properly qualified for debug/export/internal mode.
 //
@@ -87,8 +89,9 @@ var fmtpkgpfx int // %uT stickyness
 //	%-uT		type identifiers with package name instead of prefix (typesym, dcommontype, typehash)
 //
 
-func setfmode(flags *int) int {
-	fm := fmtmode
+func setfmode(flags *int) (fm int, fb bool) {
+	fm = fmtmode
+	fb = fmtbody
 	if *flags&obj.FmtSign != 0 {
 		fmtmode = FDbg
 	} else if *flags&obj.FmtSharp != 0 {
@@ -97,8 +100,12 @@ func setfmode(flags *int) int {
 		fmtmode = FTypeId
 	}
 
-	*flags &^= (obj.FmtSharp | obj.FmtLeft | obj.FmtSign)
-	return fm
+	if *flags&obj.FmtBody != 0 {
+		fmtbody = true
+	}
+
+	*flags &^= (obj.FmtSharp | obj.FmtLeft | obj.FmtSign | obj.FmtBody)
+	return
 }
 
 // Fmt "%L": Linenumbers
@@ -741,7 +748,7 @@ func typefmt(t *Type, flag int) string {
 		if name != "" {
 			str = name + " " + typ
 		}
-		if flag&obj.FmtShort == 0 && t.Note != nil {
+		if flag&obj.FmtShort == 0 && !fmtbody && t.Note != nil {
 			str += " " + strconv.Quote(*t.Note)
 		}
 		return str
@@ -1599,10 +1606,11 @@ func Sconv(s *Sym, flag int) string {
 	}
 
 	sf := flag
-	sm := setfmode(&flag)
+	sm, sb := setfmode(&flag)
 	str := symfmt(s, flag)
 	flag = sf
 	fmtmode = sm
+	fmtbody = sb
 	return str
 }
 
@@ -1625,7 +1633,7 @@ func Tconv(t *Type, flag int) string {
 
 	t.Trecur++
 	sf := flag
-	sm := setfmode(&flag)
+	sm, sb := setfmode(&flag)
 
 	if fmtmode == FTypeId && (sf&obj.FmtUnsigned != 0) {
 		fmtpkgpfx++
@@ -1641,6 +1649,7 @@ func Tconv(t *Type, flag int) string {
 	}
 
 	flag = sf
+	fmtbody = sb
 	fmtmode = sm
 	t.Trecur--
 	return str
@@ -1658,7 +1667,7 @@ func Nconv(n *Node, flag int) string {
 		return "<N>"
 	}
 	sf := flag
-	sm := setfmode(&flag)
+	sm, sb := setfmode(&flag)
 
 	var str string
 	switch fmtmode {
@@ -1675,6 +1684,7 @@ func Nconv(n *Node, flag int) string {
 	}
 
 	flag = sf
+	fmtbody = sb
 	fmtmode = sm
 	return str
 }
@@ -1691,7 +1701,7 @@ func Hconv(l *NodeList, flag int) string {
 	}
 
 	sf := flag
-	sm := setfmode(&flag)
+	sm, sb := setfmode(&flag)
 	sep := "; "
 	if fmtmode == FDbg {
 		sep = "\n"
@@ -1708,6 +1718,7 @@ func Hconv(l *NodeList, flag int) string {
 	}
 
 	flag = sf
+	fmtbody = sb
 	fmtmode = sm
 	return buf.String()
 }

src/cmd/internal/obj/fmt.go

@@ -24,4 +24,5 @@ const (
 	FmtLong
 	FmtComma
 	FmtByte
+	FmtBody // for printing export bodies
 )

test/fixedbugs/issue13777.dir/burnin.go

+package burnin
+
+type sendCmdFunc func(string)
+
+func sendCommand(c string) {}
+
+func NewSomething() {
+	// This works...
+	// var sendCmd sendCmdFunc
+	// sendCmd = sendCommand
+
+	// So does this...
+	//sendCmd := sendCmdFunc(sendCommand)
+
+	// This fails...
+	sendCmd := sendCommand
+
+	_ = sendCmd
+}

test/fixedbugs/issue13777.dir/main.go

+// build
+
+package main
+
+import (
+	x "./burnin"
+)
+
+func main() {
+	x.NewSomething()
+}

test/fixedbugs/issue13777.go

+// rundir
+
+// Copyright 2015 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 ignored