Revert #85176 addition of `clone_from` for `ManuallyDrop`
Forwarding `clone_from` to the inner value changes the observable behavior, as previously the inner value would *not* be dropped by the default implementation.
Frankly, this is a super-niche case, so #85176 is welcome to argue the behavior should be otherwise! But if we overrride it, IMO documenting the behavior would be good.
Example: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=c5d0856686fa850c1d7ee16891014efb
Make minor wording changes in a few places. Move `filter` to the
"transformations" section. Add `zip` methods to the "transformations"
section. Clarify the section about `Option` iterators, and add a section
about collecting into `Option`.
Clarify that for `Result`, `or` and `or_else` can also produce a
`Result` having a different type.
Implement nonzero arithmetics for NonZero types.
Hello'all, this is my first PR to this repo.
Non-zero natural numbers are stable by addition/multiplication/exponentiation, so it makes sense to make this arithmetic possible with `NonZeroU*`.
The major pitfall is that overflowing underlying `u*` types possibly lead to underlying `0` values, which break the major invariant of `NonZeroU*`. To accommodate it, only `checked_` and `saturating_` operations are implemented.
Other variants allowing wrapped results like `wrapping_` or `overflowing_` are ruled out *de facto*.
`impl Add<u*> for NonZeroU* { .. }` was considered, as it panics on overflow which enforces the invariant, but it does not so in release mode. I considered forcing `NonZeroU*::add` to panic in release mode by deferring the check to `u*::checked_add`, but this is less explicit for the user than directly using `NonZeroU*::checked_add`.
Following `@Lokathor's` advice on zulip, I have dropped the idea.
`@poliorcetics` on Discord also suggested implementing `_sub` operations, but I'd postpone this to another PR if there is a need for it. My opinion is that it could be useful in some cases, but that it makes less sense because non-null natural numbers are not stable by subtraction even in theory, while the overflowing problem is just about technical implementation.
One thing I don't like is that the type of the `other` arg differs in every implementation: `_add` methods accept any raw positive integer, `_mul` methods only accept non-zero values otherwise the invariant is also broken, and `_pow` only seems to accept `u32` for a reason I ignore but that seems consistent throughout `std`. Maybe there is a better way to harmonize this?
This is it, Iope I haven't forgotten anything and I'll be happy to read your feedback.
Fix an error in `map_or_else`. Use more descriptive text for
"don't care" in truth tables. Make minor corrections to truth tables.
Rename `makeiter` to `make_iter` in examples.
std: Stabilize wasm simd intrinsics
This commit performs two changes to stabilize Rust support for
WebAssembly simd intrinsics:
* The stdarch submodule is updated to pull in rust-lang/stdarch#1179.
* The `wasm_target_feature` feature gate requirement for the `simd128`
feature has been removed, stabilizing the name `simd128`.
This should conclude the FCP started on #74372 and...
Closes#74372
This commit performs two changes to stabilize Rust support for
WebAssembly simd intrinsics:
* The stdarch submodule is updated to pull in rust-lang/stdarch#1179.
* The `wasm_target_feature` feature gate requirement for the `simd128`
feature has been removed, stabilizing the name `simd128`.
This should conclude the FCP started on #74372 and...
Closes#74372
to_digit simplification (less jumps)
I just realised we might be able to make use of the fact that changing case in ascii is easy to help simplify to_digit some more.
It looks a bit cleaner and it looks like it's less jumps and there's less instructions in the generated assembly:
https://godbolt.org/z/84Erh5dhz
The benchmarks don't really tell me much. Maybe a slight improvement on the var radix.
Before:
```
test char::methods::bench_to_digit_radix_10 ... bench: 53,819 ns/iter (+/- 8,314)
test char::methods::bench_to_digit_radix_16 ... bench: 57,265 ns/iter (+/- 10,730)
test char::methods::bench_to_digit_radix_2 ... bench: 55,077 ns/iter (+/- 5,431)
test char::methods::bench_to_digit_radix_36 ... bench: 56,549 ns/iter (+/- 3,248)
test char::methods::bench_to_digit_radix_var ... bench: 43,848 ns/iter (+/- 3,189)
test char::methods::bench_to_digit_radix_10 ... bench: 51,707 ns/iter (+/- 10,946)
test char::methods::bench_to_digit_radix_16 ... bench: 52,835 ns/iter (+/- 2,689)
test char::methods::bench_to_digit_radix_2 ... bench: 51,012 ns/iter (+/- 2,746)
test char::methods::bench_to_digit_radix_36 ... bench: 53,210 ns/iter (+/- 8,645)
test char::methods::bench_to_digit_radix_var ... bench: 40,386 ns/iter (+/- 4,711)
test char::methods::bench_to_digit_radix_10 ... bench: 54,088 ns/iter (+/- 5,677)
test char::methods::bench_to_digit_radix_16 ... bench: 55,972 ns/iter (+/- 17,229)
test char::methods::bench_to_digit_radix_2 ... bench: 52,083 ns/iter (+/- 2,425)
test char::methods::bench_to_digit_radix_36 ... bench: 54,132 ns/iter (+/- 1,548)
test char::methods::bench_to_digit_radix_var ... bench: 41,250 ns/iter (+/- 5,299)
```
After:
```
test char::methods::bench_to_digit_radix_10 ... bench: 48,907 ns/iter (+/- 19,449)
test char::methods::bench_to_digit_radix_16 ... bench: 52,673 ns/iter (+/- 8,122)
test char::methods::bench_to_digit_radix_2 ... bench: 48,509 ns/iter (+/- 2,885)
test char::methods::bench_to_digit_radix_36 ... bench: 50,526 ns/iter (+/- 4,610)
test char::methods::bench_to_digit_radix_var ... bench: 38,618 ns/iter (+/- 3,180)
test char::methods::bench_to_digit_radix_10 ... bench: 54,202 ns/iter (+/- 6,994)
test char::methods::bench_to_digit_radix_16 ... bench: 56,585 ns/iter (+/- 8,448)
test char::methods::bench_to_digit_radix_2 ... bench: 50,548 ns/iter (+/- 1,674)
test char::methods::bench_to_digit_radix_36 ... bench: 52,749 ns/iter (+/- 2,576)
test char::methods::bench_to_digit_radix_var ... bench: 40,215 ns/iter (+/- 3,327)
test char::methods::bench_to_digit_radix_10 ... bench: 50,233 ns/iter (+/- 22,272)
test char::methods::bench_to_digit_radix_16 ... bench: 50,841 ns/iter (+/- 19,981)
test char::methods::bench_to_digit_radix_2 ... bench: 50,386 ns/iter (+/- 4,555)
test char::methods::bench_to_digit_radix_36 ... bench: 52,369 ns/iter (+/- 2,737)
test char::methods::bench_to_digit_radix_var ... bench: 40,417 ns/iter (+/- 2,766)
```
I removed the likely as it resulted in a few less instructions. (It's not been in there long - I added it in the last to_digit iteration).
fix off by one in `std::iter::Iterator` documentation
the range `(0..10)` is documented as "The even numbers from zero to ten." - should be ".. to nine".
Make copy/copy_nonoverlapping fn's again
Make copy/copy_nonoverlapping fn's again, rather than intrinsics.
This a short-term change to address issue #84297.
It effectively reverts PRs #81167#81238 (and part of #82967), #83091, and parts of #79684.
Revert "implement TrustedRandomAccess for Take iterator adapter"
This reverts commit 37a5b515e9 (#83990).
The original change unintentionally caused side-effects from certain iterator chains combining `take`, `zip` and `next_back()` to be omitted which is observable by user code and thus likely a breaking change
Technically one could declare it not a breaking change since `Zip`'s API contract is silent about about its backwards iteration behavior but on the other hand there is nothing in the stable Iterator API that could justify the currently observable behavior. And either way, this impact wasn't noticed or discussed in the original PR.
Fixes#85969
To remind people like me who forget about it and send PRs to make them different, and to (probably) get a test failure if the code is changed to no longer uphold it.
Clarify documentation of slice sorting methods
After reading about [this](https://polkadot.network/a-polkadot-postmortem-24-05-2021/), I realized that although the documentation of these methods is not ambiguous in its current state, it is very easy to read it and erroneously assume that their exact behaviour can be relied upon to be deterministic. Although the docs make no guarantees about which index is returned when there are multiple matches, being more explicit about when and how their determinism can be relied upon should help prevent people from making this mistake in the future.
r? ``@steveklabnik``
