unexpected shift conversion behavior

R=r
DELTA=20  (20 added, 0 deleted, 0 changed)
OCL=33646
CL=33667

test/bugs/bug193.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
+
+func main() {
+	s := uint(10);
+	ss := 1<<s;
+	y1 := float(ss);
+	y2 := float(1<<s);  // ERROR "shift"
+	y3 := string(1<<s);  // ERROR "shift"
+}

test/golden.out

@@ -168,3 +168,8 @@ bugs/bug190.go:13: invalid recursive type chan S
 bugs/bug190.go:16: invalid recursive type S
 bugs/bug190.go:15: invalid recursive type func(S) (S)
 BUG: should compile
+
+=========== bugs/bug193.go
+BUG: errchk: bugs/bug193.go:13: error message does not match 'shift'
+bugs/bug193.go:13: fatal error: optoas: no entry LSH-float
+errchk: bugs/bug193.go:14: missing expected error: 'shift'