conversion bug

R=r
DELTA=24  (24 added, 0 deleted, 0 changed)
OCL=28451
CL=28508

test/bugs/bug149.go

+// $G $D/$F.go || echo BUG: should compile
+
+// 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.
+
+package main
+
+func main() {
+	var b1 []byte;
+	s1 := string(b1);
+	println(len(s1));  // prints 0
+
+	b2 := ([]byte)(nil);
+	s2 := string(b2);
+	println(len(s2));  // prints 0
+
+	s3 := string(([]byte)(nil));  // does not compile (literal substitution of b2)
+	println(len(s3));
+}
+
+/*
+bug149.go:14: cannot convert []uint8 constant to string
+*/

test/golden.out

@@ -101,6 +101,10 @@ BUG should compile
 5 7
 BUG: should crash
 
+=========== bugs/bug149.go
+bugs/bug149.go:14: cannot convert []uint8 constant to string
+BUG: should compile
+
 =========== fixedbugs/bug016.go
 fixedbugs/bug016.go:7: constant -3 overflows uint