bug252: make ... vs ...T crossing an error, at least for now

R=r
CC=golang-dev
https://golang.org/cl/199066

src/cmd/gc/typecheck.c

@@ -1517,6 +1517,11 @@ typecheckaste(int op, Type *tstruct, NodeList *nl, char *desc)
 	for(tl=tstruct->type; tl; tl=tl->down) {
 		t = tl->type;
 		if(tl->isddd) {
+			if(nl != nil && nl->n->isddd && !eqtype(nl->n->type, t)) {
+				// TODO(rsc): This is not actually illegal but will
+				// help catch bugs.
+				yyerror("cannot pass %+N as %T (... mismatch)", nl->n, tl);
+			}
 			if(nl != nil && nl->next == nil && nl->n->isddd && eqtype(nl->n->type, t))
 				goto out;
 			for(; nl; nl=nl->next) {

test/fixedbugs/bug252.go

+// errchk $G $D/$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
+
+func f(args ...) {
+	g(args)	// ERROR "[.][.][.] mismatch"
+}
+
+func g(args ...interface{}) {
+	f(args)	// ERROR "[.][.][.] mismatch"
+}