symbol

        pub fn symbol(tag: Tag) []const u8 {
            return tag.lexeme() orelse switch (tag) {
                .invalid => "invalid token",
                .identifier => "an identifier",
                .string_literal => "a string literal",
                .multiline_string_literal_line => "a multiline string literal",
                .char_literal => "a character literal",
                .eof => "EOF",
                .builtin => "a builtin function",
                .number_literal => "a number literal",
                .doc_comment, .container_doc_comment => "a document comment",
                else => unreachable,
            };
        }