endOfBufferInString

fn endOfBufferInString(self: *@This()) !Token {
    if (self.is_end_of_input) return error.UnexpectedEndOfInput;
    const slice = self.takeValueSliceMinusTrailingOffset(switch (self.state) {
        // Don't include the escape sequence in the partial string.
        .string_backslash => 1,
        .string_backslash_u => 2,
        .string_backslash_u_1 => 3,
        .string_backslash_u_2 => 4,
        .string_backslash_u_3 => 5,
        .string_surrogate_half => 6,
        .string_surrogate_half_backslash => 7,
        .string_surrogate_half_backslash_u => 8,
        .string_surrogate_half_backslash_u_1 => 9,
        .string_surrogate_half_backslash_u_2 => 10,
        .string_surrogate_half_backslash_u_3 => 11,

        // Include everything up to the cursor otherwise.
        .string,
        .string_utf8_last_byte,
        .string_utf8_second_to_last_byte,
        .string_utf8_second_to_last_byte_guard_against_overlong,
        .string_utf8_second_to_last_byte_guard_against_surrogate_half,
        .string_utf8_third_to_last_byte,
        .string_utf8_third_to_last_byte_guard_against_overlong,
        .string_utf8_third_to_last_byte_guard_against_too_large,
        => 0,

        else => unreachable,
    });
    if (slice.len == 0) return error.BufferUnderrun;
    return Token{ .partial_string = slice };
}