Tracking issue for string-like `AsRef` coverage (original) (raw)

Almost all of the implementations of AsRef in core and std are for cheap conversions between string-like types. This tracks all of these such implementations and coordinates efforts to expand coverage.

Each column represents a type that can be converted to and each column represents a type that can be converted from. In the tables, ✅ marks an existing impl, ⚠️ marks an impl that I argue should be added, N/A marks an impl that does not make sense for that pair of types, and N/A? marks an impl that may make sense (via as_encoded_bytes). Impls that are from a more generic impl are marked with a footnote.

impl AsRef for U	AsRef	AsRef	AsRef	AsRef	AsRef<[u8]>
str	✅	✅	✅	✅	✅
String	✅	✅	✅	⚠️	✅
Cow<'_, str>	✅1	⚠️	⚠️	⚠️	⚠️
Box	✅2	⚠️	⚠️	⚠️	⚠️
Rc	✅3	⚠️	⚠️	⚠️	⚠️
Arc	✅4	⚠️	⚠️	⚠️	⚠️
UniqueRc	✅5	⚠️	⚠️	⚠️	⚠️
std:🧵:Drain<'_>	✅	⚠️	⚠️	⚠️	✅
OsStr	N/A	✅	✅	N/A?	N/A?
OsString	N/A	✅	✅	N/A?	N/A?
Cow<'_, OsStr>	N/A	✅1	✅	N/A?	N/A?
Box	N/A	✅2	⚠️	N/A?	N/A?
Rc	N/A	✅3	⚠️	N/A?	N/A?
Arc	N/A	✅4	⚠️	N/A?	N/A?
UniqueRc	N/A	✅5	⚠️	N/A?	N/A?
Path	N/A	✅	✅	N/A?	N/A?
PathBuf	N/A	✅	✅	N/A?	N/A?
Cow<'_, Path>	N/A	⚠️#139432	✅1	N/A?	N/A?
Box	N/A	⚠️	✅2	N/A?	N/A?
Rc	N/A	⚠️	✅3	N/A?	N/A?
Arc	N/A	⚠️	✅4	N/A?	N/A?
UniqueRc	N/A	⚠️	✅5	N/A?	N/A?
std::path::Component<'_>	N/A	✅	✅	N/A?	N/A?
std::path::Components<'_>	N/A	✅	✅	N/A?	N/A?
std::path::Iter<'_>	N/A	✅	✅	N/A?	N/A?
ByteStr	N/A	N/A	N/A	✅	✅
ByteString	N/A	N/A	N/A	✅	✅
Cow<'_, ByteStr>	N/A	N/A	N/A	✅1	⚠️
Box	N/A	N/A	N/A	✅2	⚠️
Rc	N/A	N/A	N/A	✅3	⚠️
Arc	N/A	N/A	N/A	✅4	⚠️
UniqueRc	N/A	N/A	N/A	✅5	⚠️
[u8]	N/A	N/A	N/A	⚠️#139441	✅6
[u8; N]	N/A	N/A	N/A	⚠️	✅7
Vec	N/A	N/A	N/A	⚠️	✅8
Cow<'_, [u8]>	N/A	N/A	N/A	⚠️	✅1
Box<[u8]>	N/A	N/A	N/A	⚠️	✅2
Rc<[u8]>	N/A	N/A	N/A	⚠️	✅3
Arc<[u8]>	N/A	N/A	N/A	⚠️	✅4
UniqueRc<[u8]>	N/A	N/A	N/A	⚠️	✅5
std::slice::Iter<'_, u8>	N/A	N/A	N/A	⚠️	✅9
std::slice::IterMut<'_, u8>	N/A	N/A	N/A	⚠️	✅10
std::vec::IntoIter	N/A	N/A	N/A	⚠️	✅11
std::vec::Drain<'_, u8>	N/A	N/A	N/A	⚠️	✅12
Simd<u8, N>	N/A	N/A	N/A	⚠️	✅13

Although CStr is string-like, its AsStr impls do not interact with other string-like types:

impl AsRef for T	AsRef
CStr	✅
CString	✅
Cow<'_, CStr>	✅1
Box	✅2
Rc	✅3
Arc	✅4
UniqueRc	✅5

Additionally, all of the above impls may be used with any number of references:

impl<T: AsRef + ?Sized, U: ?Sized> AsRef for &T impl<T: AsRef + ?Sized, U: ?Sized> AsRef for &mut T

Steps

These are the steps I plan to break this effort into:

Implement AsRef for Cow<'_, Path> #139432
Implement AsRef for [u8] #139441
Implement AsRef<{OsStr, Path}> for std:🧵:Drain<'_>.
Bring AsRef<ByteStr> up to parity with AsRef<[u8]> and implement AsRef<[u8]> for Cow<'_, ByteStr>.
Implement AsRef for Box, Rc, Arc, and UniqueRc containers on non-self types, as marked in the table.
- Add some AsRef implementations for smart pointers #139318

@rustbot claim

@rustbot label +T-libs-api

Implemented via impl<T: ToOwned + ?Sized> AsRef<T> for Cow<'_, T> ↩ ↩2 ↩3 ↩4 ↩5 ↩6
Implemented via impl<T: ?Sized, A: Allocator> AsRef<T> for Box<T, A> ↩ ↩2 ↩3 ↩4 ↩5 ↩6
Implemented via impl<T: ?Sized, A: Allocator> AsRef<T> for Rc<T, A> ↩ ↩2 ↩3 ↩4 ↩5 ↩6
Implemented via impl<T: ?Sized, A: Allocator> AsRef<T> for Arc<T, A> ↩ ↩2 ↩3 ↩4 ↩5 ↩6
Implemented via impl<T: ?Sized, A: Allocator> AsRef<T> for UniqueRc<T, A> ↩ ↩2 ↩3 ↩4 ↩5 ↩6
Implemented via impl<T> AsRef<[T]> for [T] ↩
Implemented via impl<T, const N: usize> AsRef<[T]> for [T; N] ↩
Implemented via impl<T, A: Allocator> AsRef<[T]> for Vec<T, A> ↩
Implemented via impl<T> AsRef<[T]> for std::slice::Iter<'_, T> ↩
Implemented via impl<T> AsRef<[T]> for std::slice::IterMut<'_, T> ↩
Implemented via impl<T, A: Allocator> AsRef<[T]> for std::vec::IntoIter<T, A> ↩
Implemented via impl<T, A: Allocator> AsRef<[T]> for std::vec::Drain<'_, T, A> ↩
Implemented via impl<T: SimdElement, const N: usize> AsRef<[T]> for Simd<T, N> where LaneCount<N>: SupportedLaneCount ↩

Tracking issue for string-like AsRef coverage (original) (raw)

Steps

Tracking issue for string-like `AsRef` coverage (original) (raw)