gc: bug301

Fixes #990.

R=ken2
CC=golang-dev
https://golang.org/cl/1742055

src/cmd/gc/typecheck.c

@@ -1056,7 +1056,7 @@ reswitch:
 		if(onearg(n, "panic") < 0)
 			goto error;
 		typecheck(&n->left, Erv);
-		defaultlit(&n->left, T);
+		defaultlit(&n->left, types[TINTER]);
 		if(n->left->type == T)
 			goto error;
 		goto ret;

test/fixedbugs/bug301.go

+// $G $D/$F.go || echo BUG: bug301.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.
+
+// http://code.google.com/p/go/issues/detail?id=990
+
+package main
+
+func main() {
+	defer func() {
+		if recover() != nil {
+			panic("non-nil recover")
+		}
+	}()
+	panic(nil)
+}