Add unselector_expr

src/check_expr.cpp

@@ -1353,10 +1353,7 @@ void check_is_expressible(Checker *c, Operand *o, Type *type) {
 
 bool check_is_not_addressable(Checker *c, Operand *o) {
 	if (o->mode == Addressing_OptionalOk) {
-		AstNode *expr = unparen_expr(o->expr);
-		while (expr->kind == AstNode_SelectorExpr) {
-			expr = expr->SelectorExpr.selector;
-		}
+		AstNode *expr = unselector_expr(o->expr);
 		if (expr->kind != AstNode_TypeAssertion) {
 			return true;
 		}