gc: fix shift/reduce conflict in go.y export syntax

Fixes #771.

R=ken2
CC=golang-dev
https://golang.org/cl/1267042

src/cmd/gc/go.y

@@ -74,6 +74,8 @@
 %type	<node>	indcl interfacetype structtype ptrtype
 %type	<node>	recvchantype non_recvchantype othertype fnret_type fntype
 
+%type	<val>	hidden_tag
+
 %type	<sym>	hidden_importsym hidden_pkg_importsym
 
 %type	<node>	hidden_constant hidden_literal hidden_dcl
@@ -1709,12 +1711,12 @@ hidden_dcl:
 	}
 
 hidden_structdcl:
-	sym hidden_type oliteral
+	sym hidden_type hidden_tag
 	{
 		$$ = nod(ODCLFIELD, newname($1), typenod($2));
 		$$->val = $3;
 	}
-|	'?' hidden_type oliteral
+|	'?' hidden_type hidden_tag
 	{
 		Sym *s;
 
@@ -1728,6 +1730,15 @@ hidden_structdcl:
 		$$->val = $3;
 	}
 
+hidden_tag:
+	{
+		$$.ctype = CTxxx;
+	}
+|	':' LLITERAL	// extra colon avoids conflict with "" looking like beginning of "".typename
+	{
+		$$ = $2;
+	}
+
 hidden_interfacedcl:
 	sym '(' ohidden_funarg_list ')' ohidden_funres
 	{

src/cmd/gc/subr.c

@@ -1295,8 +1295,12 @@ Tpretty(Fmt *fp, Type *t)
 				fmtprint(fp, "... %T", t->type->type);
 		} else
 			fmtprint(fp, "%T", t->type);
-		if(t->note)
-			fmtprint(fp, " \"%Z\"", t->note);
+		if(t->note) {	
+			fmtprint(fp, " ");
+			if(exporting)
+				fmtprint(fp, ":");
+			fmtprint(fp, "\"%Z\"", t->note);
+		}
 		return 0;
 
 	case TFORW:

test/fixedbugs/bug282.dir/p1.go

+// Copyright 2010 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 p1
+
+type T struct {
+	f func() "x"
+}
+

test/fixedbugs/bug282.dir/p2.go

+// Copyright 2010 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 p2
+
+import _ "./p1"
+

test/fixedbugs/bug282.go

+// $G $D/$F.dir/p1.go && $G $D/$F.dir/p2.go
+
+// 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.
+
+ignored