gc: another pointer to interface message

R=ken2
CC=golang-dev
https://golang.org/cl/4444056

src/cmd/gc/subr.c

@@ -1928,13 +1928,14 @@ assignop(Type *src, Type *dst, char **why)
 		}
 		return 0;
 	}
+	if(isptrto(dst, TINTER)) {
+		if(why != nil)
+			*why = smprint(":\n\t%T is pointer to interface, not interface", dst);
+		return 0;
+	}
 	if(src->etype == TINTER && dst->etype != TBLANK) {
-		if(why != nil) {
-			if(isptrto(dst, TINTER))
-				*why = smprint(":\n\t%T is interface, not pointer to interface", src);
-			else	
-				*why = ": need type assertion";
-		}
+		if(why != nil)
+			*why = ": need type assertion";
 		return 0;
 	}
 

test/interface/pointer.go

@@ -33,4 +33,5 @@ func main() {
 	print("call addinst\n")
 	var x Inst = AddInst(new(Start)) // ERROR "pointer to interface"
 	print("return from  addinst\n")
+	var x *Inst = new(Start)  // ERROR "pointer to interface"
 }