Cautiously add IntoIterator for arrays by value
Add the attribute described in #84133, `#[rustc_skip_array_during_method_dispatch]`, which effectively hides a trait from method dispatch when the receiver type is an array.
Then cherry-pick `IntoIterator for [T; N]` from #65819 and gate it with that attribute. Arrays can now be used as `IntoIterator` normally, but `array.into_iter()` has edition-dependent behavior, returning `slice::Iter` for 2015 and 2018 editions, or `array::IntoIter` for 2021 and later.
r? `@nikomatsakis`
cc `@LukasKalbertodt` `@rust-lang/libs`
This does not suggest adding such a function to the public API. This is
just for the purpose of avoiding duplicate code. Many array methods
already contained the same kind of code and there are still many array
related methods to come (e.g. `Iterator::{chunks, map_windows, next_n,
...}`) which all basically need this functionality. Writing custom
`unsafe` code for each of those seems not like a good idea.
Stabilize by-value `[T; N]` iterator `core::array::IntoIter`
Tracking issue: https://github.com/rust-lang/rust/issues/65798
This is unblocked now that `min_const_generics` has been stabilized in https://github.com/rust-lang/rust/pull/79135.
This PR does *not* include the corresponding `IntoIterator` impl, which is https://github.com/rust-lang/rust/pull/65819. Instead, an iterator can be constructed through the `new` method.
`new` would become unnecessary when `IntoIterator` is implemented and might be deprecated then, although it will stay stable.
These methods work very similarly to `Option`'s methods `as_ref` and
`as_mut`. They are useful in several situation, particularly when
calling other array methods (like `map`) on the result. Unfortunately,
we can't easily call them `as_ref` and `as_mut` as that would shadow
those methods on slices, thus being a breaking change (that is likely
to affect a lot of code).
Switch from indexing to zip, and also use `write` on `MaybeUninit`.
Add array_map feature to core/src/lib
Attempt to fix issue of no such feature
Update w/ pickfire's review
This changes a couple of names around, adds another small test of variable size,
and hides the rustdoc #![feature(..)].
Fmt doctest
Add suggestions from lcnr
Add basic test
And also run fmt which is where the other changes are from
Fix mut issues
These only appear when running tests, so resolved by adding mut
Swap order of forget
Add pub and rm guard impl
Add explicit type to guard
Add safety note
Change guard type from T to S
It should never have been T, as it guards over [MaybeUninit<S>; N]
Also add feature to test
This creates the language item for arrays, and adds the map fn which is like map in options or
iterators. It currently allocates an extra array, unfortunately.
Added fixme for transmuting
Fix typo
Add drop guard
