Bug involving ... initializers and interface values.

R=rsc
APPROVED=rsc
DELTA=22  (22 added, 0 deleted, 0 changed)
OCL=33053
CL=33104

test/bugs/bug187.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.
+
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+package main
+
+func main() {
+	// This bug doesn't arise with [...]int, or []interface{} or [3]interface{}.
+	a := [...]interface{} { 1, 2, 3 };
+	n := 0;
+	for _, v := range a {
+		if v.(int) != n {
+			panicln("BUG:", n, v.(int));
+		}
+		n++;
+	}
+}

test/golden.out

@@ -153,3 +153,10 @@ BUG: should fail
 
 =========== bugs/bug169.go
 BUG: errchk: command succeeded unexpectedly
+
+=========== bugs/bug187.go
+BUG: 0 1
+SIGSEGV: segmentation violation
+Faulting address: 0x40a1f0
+PC=0x40a1f0
+