Document implementable/unimplementable

components/collections/src/codepointtrie/cptrie.rs

@@ -53,6 +53,8 @@ pub enum TrieType {
 
 /// A trait representing the values stored in the data array of a [`CodePointTrie`].
 /// This trait is used as a type parameter in constructing a `CodePointTrie`.
+///
+/// This trait can be implemented on anything that can be represented as a u32s worth of data.
 pub trait TrieValue: Copy + Eq + PartialEq + zerovec::ule::AsULE + 'static {
     /// Last-resort fallback value to return if we cannot read data from the trie.
     ///

components/datetime/src/scaffold/calendar.rs

@@ -382,6 +382,7 @@ impl_load_any_calendar!([
 ]);
 
 /// A type that can be converted into a specific calendar system.
+// This trait is implementable
 pub trait ConvertCalendar {
     /// The converted type. This can be the same as the receiver type.
     type Converted<'a>: Sized;
@@ -441,6 +442,7 @@ impl<O: TimeZoneModel> ConvertCalendar for TimeZoneInfo<O> {
 }
 
 /// An input that may be associated with a specific runtime calendar.
+// This trait is implementable
 pub trait InSameCalendar {
     /// Checks whether this type is compatible with the given calendar.
     ///
@@ -514,6 +516,7 @@ impl<O: TimeZoneModel> InSameCalendar for TimeZoneInfo<O> {
 }
 
 /// An input associated with a fixed, static calendar.
+// This trait is implementable
 pub trait InFixedCalendar<C> {}
 
 impl<C: CldrCalendar, A: AsCalendar<Calendar = C>> InFixedCalendar<C> for Date<A> {}

components/datetime/src/scaffold/fieldset_traits.rs

@@ -156,6 +156,7 @@ pub trait DateTimeMarkers: Sealed + DateTimeNamesMarker {
 /// - [`TimeZoneInfo`](icu_timezone::TimeZoneInfo)
 ///
 /// [`fieldsets::YMD`]: crate::fieldsets::YMD
+// This trait is implicitly sealed due to its blanket impl
 pub trait AllInputMarkers<R: DateTimeMarkers>:
     GetField<<R::D as DateInputMarkers>::YearInput>
     + GetField<<R::D as DateInputMarkers>::MonthInput>
@@ -204,6 +205,7 @@ where
 ///
 /// This trait is implemented on all providers that support datetime formatting,
 /// including [`crate::provider::Baked`].
+// This trait is implicitly sealed due to its blanket impl
 pub trait AllFixedCalendarFormattingDataMarkers<C: CldrCalendar, FSet: DateTimeMarkers>:
     DataProvider<<FSet::D as TypedDateDataMarkers<C>>::YearNamesV1Marker>
     + DataProvider<<FSet::D as TypedDateDataMarkers<C>>::MonthNamesV1Marker>
@@ -256,6 +258,7 @@ where
 ///
 /// This trait is implemented on all providers that support datetime formatting,
 /// including [`crate::provider::Baked`].
+// This trait is implicitly sealed due to its blanket impl
 pub trait AllAnyCalendarFormattingDataMarkers<FSet: DateTimeMarkers>:
     DataProvider<<<FSet::D as DateDataMarkers>::Year as CalMarkers<YearNamesV1Marker>>::Buddhist>
     + DataProvider<<<FSet::D as DateDataMarkers>::Year as CalMarkers<YearNamesV1Marker>>::Chinese>
@@ -400,6 +403,7 @@ where
 
 /// Trait to consolidate data provider markers external to this crate
 /// for datetime formatting with a fixed calendar.
+// This trait is implicitly sealed due to its blanket impl
 pub trait AllFixedCalendarExternalDataMarkers:
     DataProvider<DecimalSymbolsV2Marker> + DataProvider<DecimalDigitsV1Marker>
 {
@@ -412,6 +416,7 @@ impl<T> AllFixedCalendarExternalDataMarkers for T where
 
 /// Trait to consolidate data provider markers external to this crate
 /// for datetime formatting with any calendar.
+// This trait is implicitly sealed due to its blanket impl
 pub trait AllAnyCalendarExternalDataMarkers:
     DataProvider<ChineseCacheV1Marker>
     + DataProvider<DangiCacheV1Marker>

components/datetime/src/scaffold/names_storage.rs

@@ -334,6 +334,7 @@ where
 /// is_trait_implemented::<TimeFieldSet, CompositeFieldSet>();
 /// ```
 #[allow(missing_docs)]
+// This trait is implicitly sealed by deriving from a sealed trait
 pub trait DateTimeNamesFrom<M: DateTimeNamesMarker>: DateTimeNamesMarker {
     fn map_year_names(
         other: <M::YearNames as NamesContainer<YearNamesV1Marker, YearNameLength>>::Container,

components/pattern/src/common.rs

@@ -115,6 +115,8 @@ pub trait PatternBackend: crate::private::Sealed + 'static + core::fmt::Debug {
 /// This trait can add [`Part`]s for individual literals or placeholders. The implementations
 /// of this trait on standard types do not add any [`Part`]s.
 ///
+/// This trait is not implementable by user code due to the blanket impl.
+///
 /// # Examples
 ///
 /// A custom implementation that adds parts:

components/properties/src/names.rs

@@ -650,6 +650,7 @@ pub trait ParseableEnumeratedProperty: crate::private::Sealed + TrieValue {
 }
 
 // Abstract over Linear/Sparse/Script representation
+// This trait is implicitly sealed by not being exported.
 pub trait PropertyEnumToValueNameLookup {
     fn get(&self, prop: u32) -> Option<&str>;
 }