gc: say that shift must be unsigned integer

R=ken2
CC=golang-dev
https://golang.org/cl/2519044

diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 9466c39c1446a7c0ec5ea4b3cdc85c908f1477bf..89cd1d65917a04c7cbd2f870889b917390c9175e 100644 (file)
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -425,7 +425,7 @@ reswitch:
                n->right = r;
                t = r->type;
                if(!isint[t->etype] || issigned[t->etype]) {
-                       yyerror("invalid operation: %#N (shift count type %T)", n, r->type);
+                       yyerror("invalid operation: %#N (shift count type %T, must be unsigned integer)", n, r->type);
                        goto error;
                }
                t = l->type;