Add AsLanguageTag trait.

CHANGELOG.md

@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.3.4]
+### Added
+- Add `AsLanguageTag` trait.
+
 ## [0.2.0]
 ### Changed
 - `LanguageTagBuf::as_ref` now returns a `LanguageTag<&[u8]>`.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "langtag"
-version = "0.3.3"
+version = "0.3.4"
 authors = ["Timothée Haudebourg <author@haudebourg.net>"]
 edition = "2018"
 categories = ["parsing", "data-structures"]

src/as_ref.rs

@@ -0,0 +1,8 @@
+use crate::LanguageTag;
+
+/// Type that can be borrowed as a [`LanguageTag`] reference.
+///
+/// This is the equivalent of `AsRef` for `LanguageTag`.
+pub trait AsLanguageTag<T: ?Sized = [u8]> {
+	fn as_language_tag(&self) -> LanguageTag<T>;
+}

src/lib.rs

@@ -391,6 +391,7 @@ macro_rules! iterator {
 	};
 }
 
+mod as_ref;
 mod error;
 mod extension;
 mod grandfathered;
@@ -401,6 +402,7 @@ mod privateuse;
 mod variant;
 
 pub use self::langtag::*;
+pub use as_ref::*;
 pub use error::*;
 pub use extension::*;
 pub use grandfathered::*;
@@ -473,6 +475,12 @@ impl LanguageTagBuf {
 	}
 }
 
+impl<T: AsRef<[u8]>> AsLanguageTag<[u8]> for LanguageTagBuf<T> {
+	fn as_language_tag(&self) -> LanguageTag<[u8]> {
+		self.as_ref()
+	}
+}
+
 macro_rules! language_tag_impl {
 	() => {
 		/// Returns the bytes representation of the language tag.
@@ -586,6 +594,12 @@ macro_rules! language_tag_impl {
 	};
 }
 
+impl<'a, T: ?Sized> AsLanguageTag<T> for LanguageTag<'a, T> {
+	fn as_language_tag(&self) -> LanguageTag<T> {
+		*self
+	}
+}
+
 impl<'a, T: AsRef<[u8]> + ?Sized> LanguageTag<'a, T> {
 	language_tag_impl!();
 }