lang: ast: implement cascade operator parsing

lang/ast/expr/expr.c

@@ -31,6 +31,7 @@ struct ast_node_type expr_node_ops = {
 	.n_symbol_parsers = {
 		SYM_PARSER(LEFT_PAREN, arith_parse_left_paren),
 		SYM_PARSER(RIGHT_PAREN, arith_parse_right_paren),
+		SYM_PARSER(SEMICOLON, arith_parse_semicolon),
 		SYM_PARSER(DOT, arith_parse_dot),
 	},
 };