Don't re-export datetime::Length. Improve rust links and allowlist (#6446)

Author: sffc

README.md

@@ -37,7 +37,7 @@ icu = "1.5.0"
 
 ```rust
 use icu::calendar::Date;
-use icu::datetime::{DateTimeFormatter, Length, fieldsets::YMD};
+use icu::datetime::{DateTimeFormatter, fieldsets::YMD};
 use icu::locale::locale;
 
 let dtf = DateTimeFormatter::try_new(

components/datetime/src/builder.rs

@@ -154,6 +154,22 @@ impl DateFields {
         Self::YM,
         Self::Y,
     ];
+
+    /// Returns whether this [`DateFields`] variant represents a [`CalendarPeriodFieldSet`].
+    pub fn is_calendar_period(self) -> bool {
+        match self {
+            DateFields::D => false,
+            DateFields::MD => false,
+            DateFields::YMD => false,
+            DateFields::DE => false,
+            DateFields::MDE => false,
+            DateFields::YMDE => false,
+            DateFields::E => false,
+            DateFields::M => true,
+            DateFields::YM => true,
+            DateFields::Y => true,
+        }
+    }
 }
 
 /// An enumeration over all possible time zone styles.

components/datetime/src/lib.rs

@@ -118,7 +118,6 @@ pub use neo::FixedCalendarDateTimeFormatter;
 pub use neo::FormattedDateTime;
 pub use neo::FormattedDateTimeUnchecked;
 pub use neo::NoCalendarFormatter;
-pub use options::Length;
 
 /// Locale preferences used by this crate
 pub mod preferences {

components/datetime/src/provider/packed_pattern.rs

@@ -8,7 +8,7 @@ use super::pattern::{
     runtime::{Pattern, PatternBorrowed, PatternMetadata},
     PatternItem,
 };
-use crate::{size_test_macro::size_test, Length};
+use crate::{options::Length, size_test_macro::size_test};
 use alloc::vec::Vec;
 use icu_plurals::{
     provider::{FourBitMetadata, PluralElementsPackedULE},

components/icu/README.md

@@ -28,7 +28,7 @@
 //! Compiled data is exposed through idiomatic Rust constructors like `new` or `try_new`:
 //!
 //! ```
-//! use icu::datetime::{fieldsets::YMD, DateTimeFormatter, Length};
+//! use icu::datetime::{fieldsets::YMD, DateTimeFormatter};
 //! use icu::locale::locale;
 //!
 //! let dtf =
@@ -49,7 +49,7 @@
 //! special constructors:
 //!
 //! ```no_run
-//! use icu::datetime::{fieldsets::YMD, DateTimeFormatter, Length};
+//! use icu::datetime::{fieldsets::YMD, DateTimeFormatter};
 //! use icu::locale::fallback::LocaleFallbacker;
 //! use icu::locale::locale;
 //! use icu_provider_adapters::fallback::LocaleFallbackProvider;