gc: interface error message fixes
Fixes #1526.
R=ken2
CC=golang-dev
https://golang.org/cl/4190051
diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 0755ca3..49df503 100644
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -1909,8 +1909,12 @@
return 0;
}
if(src->etype == TINTER && dst->etype != TBLANK) {
- if(why != nil)
- *why = ": need type assertion";
+ if(why != nil) {
+ if(isptrto(dst, TINTER))
+ *why = smprint(":\n\t%T is interface, not pointer to interface", src);
+ else
+ *why = ": need type assertion";
+ }
return 0;
}
diff --git a/src/cmd/gc/typecheck.c b/src/cmd/gc/typecheck.c
index 5edca96..731e5a4 100644
--- a/src/cmd/gc/typecheck.c
+++ b/src/cmd/gc/typecheck.c
@@ -1613,7 +1613,7 @@
exportassignok(tn->type, desc);
if(assignop(tn->type, tl->type->type, &why) == 0) {
if(call != N)
- yyerror("cannot use %T as type %T in argument to %#N%s", tn->type, tl->type->type, desc, call, why);
+ yyerror("cannot use %T as type %T in argument to %#N%s", tn->type, tl->type->type, call, why);
else
yyerror("cannot use %T as type %T in %s%s", tn->type, tl->type->type, desc, why);
}
@@ -1625,7 +1625,7 @@
exportassignok(tn->type, desc);
if(assignop(tn->type, tl->type, &why) == 0) {
if(call != N)
- yyerror("cannot use %T as type %T in argument to %#N%s", tn->type, tl->type, desc, call, why);
+ yyerror("cannot use %T as type %T in argument to %#N%s", tn->type, tl->type, call, why);
else
yyerror("cannot use %T as type %T in %s%s", tn->type, tl->type, desc, why);
}
