gc: syntax error for incomplete chan type

Fixes #932.

R=rsc
CC=golang-dev
https://golang.org/cl/3515041

src/cmd/gc/go.errors

@@ -35,6 +35,15 @@ static struct {
 	% loadsys package imports LTYPE LNAME ';'
 	"unexpected semicolon or newline in type declaration",
 
+	% loadsys package imports LCHAN '}'
+	"unexpected } in channel type",
+	
+	% loadsys package imports LCHAN ')'
+	"unexpected ) in channel type",
+	
+	% loadsys package imports LCHAN ','
+	"unexpected comma in channel type",
+
 	% loadsys package imports LFUNC LNAME '(' ')' '{' if_stmt ';' LELSE
 	"unexpected semicolon or newline before else",
 

test/syntax/chan.go

+// errchk $G -e $D/$F.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.
+
+package main
+
+type xyz struct {
+    ch chan
+} // ERROR "unexpected } in channel type"
+
+func Foo(y chan) { // ERROR "unexpected \) in channel type"
+}
+
+func Bar(x chan, y int) { // ERROR "unexpected comma in channel type"
+}