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diff --git a/vendor/icu_locid/src/extensions/mod.rs b/vendor/icu_locid/src/extensions/mod.rs
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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
+// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+//! Unicode Extensions provide a mechanism to extend the [`LanguageIdentifier`] with
+//! additional bits of information - a combination of a [`LanguageIdentifier`] and [`Extensions`]
+//! is called [`Locale`].
+//!
+//! There are four types of extensions:
+//!
+//!  * [`Unicode Extensions`] - marked as `u`.
+//!  * [`Transform Extensions`] - marked as `t`.
+//!  * [`Private Use Extensions`] - marked as `x`.
+//!  * [`Other Extensions`] - marked as any `a-z` except of `u`, `t` and `x`.
+//!
+//! One can think of extensions as a bag of extra information on top of basic 4 [`subtags`].
+//!
+//! Notice: `Other` extension type is currently not supported.
+//!
+//! # Examples
+//!
+//! ```
+//! use icu::locid::extensions::unicode::{Key, Value};
+//! use icu::locid::Locale;
+//!
+//! let loc: Locale = "en-US-u-ca-buddhist-t-en-US-h0-hybrid-x-foo"
+//!     .parse()
+//!     .expect("Failed to parse.");
+//!
+//! assert_eq!(loc.id.language, "en".parse().unwrap());
+//! assert_eq!(loc.id.script, None);
+//! assert_eq!(loc.id.region, Some("US".parse().unwrap()));
+//! assert_eq!(loc.id.variants.len(), 0);
+//!
+//! let key: Key = "ca".parse().expect("Parsing key failed.");
+//! let value: Value = "buddhist".parse().expect("Parsing value failed.");
+//! assert_eq!(loc.extensions.unicode.keywords.get(&key), Some(&value));
+//! ```
+//!
+//! [`LanguageIdentifier`]: super::LanguageIdentifier
+//! [`Locale`]: super::Locale
+//! [`subtags`]: super::subtags
+//! [`Other Extensions`]: other
+//! [`Private Use Extensions`]: private
+//! [`Transform Extensions`]: transform
+//! [`Unicode Extensions`]: unicode
+pub mod other;
+pub mod private;
+pub mod transform;
+pub mod unicode;
+
+use other::Other;
+use private::Private;
+use transform::Transform;
+use unicode::Unicode;
+
+use alloc::vec::Vec;
+
+use crate::parser::ParserError;
+use crate::parser::SubtagIterator;
+
+/// Defines the type of extension.
+#[derive(Debug, PartialEq, Eq, Clone, Hash, PartialOrd, Ord, Copy)]
+#[non_exhaustive]
+pub enum ExtensionType {
+    /// Transform Extension Type marked as `t`.
+    Transform,
+    /// Unicode Extension Type marked as `u`.
+    Unicode,
+    /// Private Extension Type marked as `x`.
+    Private,
+    /// All other extension types.
+    Other(u8),
+}
+
+impl ExtensionType {
+    pub(crate) const fn try_from_byte(key: u8) -> Result<Self, ParserError> {
+        let key = key.to_ascii_lowercase();
+        match key {
+            b'u' => Ok(Self::Unicode),
+            b't' => Ok(Self::Transform),
+            b'x' => Ok(Self::Private),
+            b'a'..=b'z' => Ok(Self::Other(key)),
+            _ => Err(ParserError::InvalidExtension),
+        }
+    }
+
+    pub(crate) const fn try_from_bytes_manual_slice(
+        bytes: &[u8],
+        start: usize,
+        end: usize,
+    ) -> Result<Self, ParserError> {
+        if end - start != 1 {
+            return Err(ParserError::InvalidExtension);
+        }
+        #[allow(clippy::indexing_slicing)]
+        Self::try_from_byte(bytes[start])
+    }
+}
+
+/// A map of extensions associated with a given [`Locale`](crate::Locale).
+#[derive(Debug, Default, PartialEq, Eq, Clone, Hash)]
+#[non_exhaustive]
+pub struct Extensions {
+    /// A representation of the data for a Unicode extension, when present in the locale identifer.
+    pub unicode: Unicode,
+    /// A representation of the data for a transform extension, when present in the locale identifer.
+    pub transform: Transform,
+    /// A representation of the data for a private-use extension, when present in the locale identifer.
+    pub private: Private,
+    /// A sequence of any other extensions that are present in the locale identifier but are not formally
+    /// [defined](https://unicode.org/reports/tr35/) and represented explicitly as [`Unicode`], [`Transform`],
+    /// and [`Private`] are.
+    pub other: Vec<Other>,
+}
+
+impl Extensions {
+    /// Returns a new empty map of extensions. Same as [`default()`](Default::default()), but is `const`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use icu::locid::extensions::Extensions;
+    ///
+    /// assert_eq!(Extensions::new(), Extensions::default());
+    /// ```
+    #[inline]
+    pub const fn new() -> Self {
+        Self {
+            unicode: Unicode::new(),
+            transform: Transform::new(),
+            private: Private::new(),
+            other: Vec::new(),
+        }
+    }
+
+    /// Function to create a new map of extensions containing exactly one unicode extension, callable in `const`
+    /// context.
+    #[inline]
+    pub const fn from_unicode(unicode: Unicode) -> Self {
+        Self {
+            unicode,
+            transform: Transform::new(),
+            private: Private::new(),
+            other: Vec::new(),
+        }
+    }
+
+    /// Returns whether there are no extensions present.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use icu::locid::Locale;
+    ///
+    /// let loc: Locale = "en-US-u-foo".parse().expect("Parsing failed.");
+    ///
+    /// assert!(!loc.extensions.is_empty());
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        self.unicode.is_empty()
+            && self.transform.is_empty()
+            && self.private.is_empty()
+            && self.other.is_empty()
+    }
+
+    /// Retains the specified extension types, clearing all others.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use icu::locid::extensions::ExtensionType;
+    /// use icu::locid::Locale;
+    ///
+    /// let loc: Locale =
+    ///     "und-a-hello-t-mul-u-world-z-zzz-x-extra".parse().unwrap();
+    ///
+    /// let mut only_unicode = loc.clone();
+    /// only_unicode
+    ///     .extensions
+    ///     .retain_by_type(|t| t == ExtensionType::Unicode);
+    /// assert_eq!(only_unicode, "und-u-world".parse().unwrap());
+    ///
+    /// let mut only_t_z = loc.clone();
+    /// only_t_z.extensions.retain_by_type(|t| {
+    ///     t == ExtensionType::Transform || t == ExtensionType::Other(b'z')
+    /// });
+    /// assert_eq!(only_t_z, "und-t-mul-z-zzz".parse().unwrap());
+    /// ```
+    pub fn retain_by_type<F>(&mut self, mut predicate: F)
+    where
+        F: FnMut(ExtensionType) -> bool,
+    {
+        if !predicate(ExtensionType::Unicode) {
+            self.unicode.clear();
+        }
+        if !predicate(ExtensionType::Transform) {
+            self.transform.clear();
+        }
+        if !predicate(ExtensionType::Private) {
+            self.private.clear();
+        }
+        self.other
+            .retain(|o| predicate(ExtensionType::Other(o.get_ext_byte())));
+    }
+
+    pub(crate) fn try_from_iter(iter: &mut SubtagIterator) -> Result<Self, ParserError> {
+        let mut unicode = None;
+        let mut transform = None;
+        let mut private = None;
+        let mut other = Vec::new();
+
+        let mut st = iter.next();
+        while let Some(subtag) = st {
+            match subtag.get(0).map(|b| ExtensionType::try_from_byte(*b)) {
+                Some(Ok(ExtensionType::Unicode)) => {
+                    unicode = Some(Unicode::try_from_iter(iter)?);
+                }
+                Some(Ok(ExtensionType::Transform)) => {
+                    transform = Some(Transform::try_from_iter(iter)?);
+                }
+                Some(Ok(ExtensionType::Private)) => {
+                    private = Some(Private::try_from_iter(iter)?);
+                }
+                Some(Ok(ExtensionType::Other(ext))) => {
+                    let parsed = Other::try_from_iter(ext, iter)?;
+                    if let Err(idx) = other.binary_search(&parsed) {
+                        other.insert(idx, parsed);
+                    } else {
+                        return Err(ParserError::InvalidExtension);
+                    }
+                }
+                None => {}
+                _ => return Err(ParserError::InvalidExtension),
+            }
+
+            st = iter.next();
+        }
+
+        Ok(Self {
+            unicode: unicode.unwrap_or_default(),
+            transform: transform.unwrap_or_default(),
+            private: private.unwrap_or_default(),
+            other,
+        })
+    }
+
+    pub(crate) fn for_each_subtag_str<E, F>(&self, f: &mut F) -> Result<(), E>
+    where
+        F: FnMut(&str) -> Result<(), E>,
+    {
+        let mut wrote_tu = false;
+        // Alphabetic by singleton
+        self.other.iter().try_for_each(|other| {
+            if other.get_ext() > 't' && !wrote_tu {
+                // Since 't' and 'u' are next to each other in alphabetical
+                // order, write both now.
+                self.transform.for_each_subtag_str(f)?;
+                self.unicode.for_each_subtag_str(f)?;
+                wrote_tu = true;
+            }
+            other.for_each_subtag_str(f)?;
+            Ok(())
+        })?;
+
+        if !wrote_tu {
+            self.transform.for_each_subtag_str(f)?;
+            self.unicode.for_each_subtag_str(f)?;
+        }
+
+        // Private must be written last, since it allows single character
+        // keys. Extensions must also be written in alphabetical order,
+        // which would seem to imply that other extensions `y` and `z` are
+        // invalid, but this is not specified.
+        self.private.for_each_subtag_str(f)?;
+        Ok(())
+    }
+}
+
+impl_writeable_for_each_subtag_str_no_test!(Extensions);
+
+#[test]
+fn test_writeable() {
+    use crate::Locale;
+    use writeable::assert_writeable_eq;
+    assert_writeable_eq!(Extensions::new(), "",);
+    assert_writeable_eq!(
+        "my-t-my-d0-zawgyi".parse::<Locale>().unwrap().extensions,
+        "t-my-d0-zawgyi",
+    );
+    assert_writeable_eq!(
+        "ar-SA-u-ca-islamic-civil"
+            .parse::<Locale>()
+            .unwrap()
+            .extensions,
+        "u-ca-islamic-civil",
+    );
+    assert_writeable_eq!(
+        "en-001-x-foo-bar".parse::<Locale>().unwrap().extensions,
+        "x-foo-bar",
+    );
+    assert_writeable_eq!(
+        "und-t-m0-true".parse::<Locale>().unwrap().extensions,
+        "t-m0-true",
+    );
+    assert_writeable_eq!(
+        "und-a-foo-t-foo-u-foo-w-foo-z-foo-x-foo"
+            .parse::<Locale>()
+            .unwrap()
+            .extensions,
+        "a-foo-t-foo-u-foo-w-foo-z-foo-x-foo",
+    );
+}