gc: fix import of struct type in struct literal

Fixes #2716.

R=ken2
CC=golang-dev
https://golang.org/cl/5652065

src/cmd/gc/go.y

@@ -987,7 +987,10 @@ lbrace:
 new_name:
 	sym
 	{
-		$$ = newname($1);
+		if($1 == S)
+			$$ = N;
+		else
+			$$ = newname($1);
 	}
 
 dcl_name:
@@ -1418,6 +1421,19 @@ structdcl:
 	{
 		NodeList *l;
 
+		Node *n;
+		if(l != nil && l->next == nil && l->n == nil) {
+			// ? symbol, during import
+			n = $2;
+			if(n->op == OIND)
+				n = n->left;
+			n = embedded(n->sym);
+			n->right = $2;
+			n->val = $3;
+			$$ = list1(n);
+			break;
+		}
+
 		for(l=$1; l; l=l->next) {
 			l->n = nod(ODCLFIELD, l->n, $2);
 			l->n->val = $3;

test/fixedbugs/bug415.dir/main.go

+// 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 main
+import "./p"
+func main() {}
+var _ p.A
+

test/fixedbugs/bug415.dir/p.go

+// 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 p
+
+type A struct {
+	s struct{int}
+}
+
+func (a *A) f() {
+	a.s = struct{int}{0}
+}
+

test/fixedbugs/bug415.go

+// $G $D/$F.dir/p.go && $G $D/$F.dir/main.go
+
+// 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.
+
+// Issue 2716.  Export metadata error made main.go not compile.
+
+package ignored