Check for invalid uses of ... in builtin function calls.

From-SVN: r171544

gcc/go/gofrontend/expressions.cc

@@ -6672,6 +6672,12 @@ Find_call_expression::expression(Expression** pexpr)
 Expression*
 Builtin_call_expression::do_lower(Gogo* gogo, Named_object* function, int)
 {
+  if (this->is_varargs() && this->code_ != BUILTIN_APPEND)
+    {
+      this->report_error(_("invalid use of %<...%> with builtin function"));
+      return Expression::make_error(this->location());
+    }
+
   if (this->code_ == BUILTIN_NEW)
     {
       const Expression_list* args = this->args();

gcc/go/gofrontend/parse.cc

@@ -2705,6 +2705,12 @@ Parse::primary_expr(bool may_be_sink, bool may_be_composite_lit,
 	  this->advance_token();
 	  Expression* expr = this->expression(PRECEDENCE_NORMAL, false, true,
 					      NULL);
+	  if (this->peek_token()->is_op(OPERATOR_ELLIPSIS))
+	    {
+	      error_at(this->location(),
+		       "invalid use of %<...%> in type conversion");
+	      this->advance_token();
+	    }
 	  if (!this->peek_token()->is_op(OPERATOR_RPAREN))
 	    error_at(this->location(), "expected %<)%>");
 	  else