feat(intl): implement Intl.Locale (#5344)

crates/perry-runtime/Cargo.toml

@@ -79,7 +79,11 @@ intl-segmenter = ["dep:unicode-segmentation"]
 # it (the compiler enables it on `Intl.getCanonicalLocales`/`supportedLocalesOf`
 # usage). Already pulled transitively by `temporal`, so default/shipped builds
 # carry no extra weight. A hand-rolled structural fallback covers the off case.
-intl-locale = ["dep:icu_locale_core"]
+# `icu_locale_core/alloc` is required for `Locale::try_from_str`/`normalize` and
+# the mutable `Keywords`/`Variants` builders `Intl.Locale` uses; without it the
+# auto-optimize build of a Temporal-free program that touches `Intl.Locale`
+# would fail (alloc was previously only pulled in transitively by `temporal`).
+intl-locale = ["dep:icu_locale_core", "icu_locale_core/alloc"]
 # `full` only opt-ins the small Node-API helpers (os.hostname / os.homedir).
 # `postgres`, `redis`, `whoami` were previously listed here but were either
 # unimported (postgres, whoami) or only used by a now-deleted `redis_client.rs`

crates/perry-runtime/src/intl.rs

@@ -1647,6 +1647,19 @@ fn set_proto_to_string_tag(proto: *mut ObjectHeader, tag: &str) {
     );
 }
 
+// ---- Intl.Locale -----------------------------------------------------------
+// Implemented in the `locale` submodule (gated on `intl-locale`); kept separate
+// so `intl.rs` stays under the file-size gate.
+#[cfg(feature = "intl-locale")]
+mod locale;
+#[cfg(feature = "intl-locale")]
+pub(crate) use locale::{install_locale_constructor, is_locale_ctor};
+
+#[cfg(not(feature = "intl-locale"))]
+pub(crate) fn is_locale_ctor(_func_value: f64) -> bool {
+    false
+}
+
 fn install_constructor(
     ns_obj: *mut ObjectHeader,
     name: &str,
@@ -1831,4 +1844,9 @@ pub fn install_intl_namespace(ns_obj: *mut ObjectHeader) {
             ),
         ],
     );
+    // `Intl.Locale` needs the `icu_locale_core` BCP-47 parser (gated on the
+    // `intl-locale` feature, enabled by the compiler when a program references
+    // `Intl.Locale`).
+    #[cfg(feature = "intl-locale")]
+    install_locale_constructor(ns_obj);
 }