gc: top-level closure bug

Fixes #2055.

R=ken2
CC=golang-dev
https://golang.org/cl/4816059

src/cmd/gc/closure.c

@@ -84,6 +84,11 @@ typecheckclosure(Node *func, int top)
 	oldfn = curfn;
 	typecheck(&func->ntype, Etype);
 	func->type = func->ntype->type;
+	if(curfn == nil) {
+		xtop = list(xtop, func);
+		return;
+	}
+
 	if(func->type != T) {
 		curfn = func;
 		typechecklist(func->nbody, Etop);

src/cmd/gc/lex.c

@@ -255,7 +255,7 @@ main(int argc, char *argv[])
 	resumecheckwidth();
 
 	for(l=xtop; l; l=l->next)
-		if(l->n->op == ODCLFUNC) {
+		if(l->n->op == ODCLFUNC || l->n->op == OCLOSURE) {
 			curfn = l->n;
 			saveerrors();
 			typechecklist(l->n->nbody, Etop);
@@ -274,8 +274,9 @@ main(int argc, char *argv[])
 	while(closures) {
 		l = closures;
 		closures = nil;
-		for(; l; l=l->next)
+		for(; l; l=l->next) {
 			funccompile(l->n, 1);
+		}
 	}
 
 	for(l=externdcl; l; l=l->next)

test/fixedbugs/bug355.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// 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.
+
+package main
+
+var f = func() int {
+	type S int
+	return 42
+}
+
+func main() {
+	if f() != 42 {
+		panic("BUG: bug355")
+	}
+}