6g bug: struct initializers must provide all field values unless the fields are named

R=rsc,r
DELTA=16  (16 added, 0 deleted, 0 changed)
OCL=33292
CL=33303

test/bugs/bug189.go

+// errchk $G $D/$F.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.
+
+package main
+
+type S struct {
+	a, b int
+}
+
+func main() {
+	s1 := S{a: 7};	// ok - field is named
+	s3 := S{7, 11};	// ok - all fields have values
+	s2 := S{7};	// bug - should not compile since not all fields have values
+}

test/golden.out

@@ -156,3 +156,6 @@ BUG: errchk: command succeeded unexpectedly
 
 =========== bugs/bug187.go
 BUG: 0 1
+
+=========== bugs/bug189.go
+BUG: errchk: command succeeded unexpectedly