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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
impl_tinystr_subtag!(
/// A key used in a list of [`Keywords`](super::Keywords).
///
/// The key has to be a two ASCII alphanumerical characters long, with the first
/// character being alphanumeric, and the second being alphabetic.
///
///
/// # Examples
///
/// ```
/// use icu::locid::extensions::unicode::Key;
///
/// assert!("ca".parse::<Key>().is_ok());
/// ```
Key,
extensions::unicode,
key,
extensions_unicode_key,
2..=2,
s,
s.all_bytes()[0].is_ascii_alphanumeric() && s.all_bytes()[1].is_ascii_alphabetic(),
s.to_ascii_lowercase(),
(s.all_bytes()[0].is_ascii_lowercase() || s.all_bytes()[0].is_ascii_digit())
&& s.all_bytes()[1].is_ascii_lowercase(),
InvalidExtension,
["ca", "8a"],
["a", "a8", "abc"],
);