Add `unwrap_unchecked()` methods for `Option` and `Result`
In particular:
- `unwrap_unchecked()` for `Option`.
- `unwrap_unchecked()` and `unwrap_err_unchecked()` for `Result`.
These complement other `*_unchecked()` methods in `core` etc.
Currently there are a couple of places it may be used inside rustc (`LinkedList`, `BTree`). It is also easy to find other repositories with similar functionality.
Fixes#48278.
Prevent query cycles in the MIR inliner
r? `@eddyb` `@wesleywiser`
cc `@rust-lang/wg-mir-opt`
The general design is that we have a new query that is run on the `validated_mir` instead of on the `optimized_mir`. That query is forced before going into the optimization pipeline, so as to not try to read from a stolen MIR.
The query should not be cached cross crate, as you should never call it for items from other crates. By its very design calls into other crates can never cause query cycles.
This is a pessimistic approach to inlining, since we strictly have more calls in the `validated_mir` than we have in `optimized_mir`, but that's not a problem imo.
More clear documentation for NonNull<T>
Rephrase and hopefully clarify the discussion of covariance in `NonNull<T>` documentation.
I'm very much not an expert so someone should definitely double check the correctness of what I'm saying. At the same time, the new language makes more sense to me, so hopefully it also is more logical to others whose knowledge of covariance basically begins and ends with the [Rustonomicon chapter](https://doc.rust-lang.org/nomicon/subtyping.html).
Related to #48929.
Change branching in `iter.skip()`
Optimize branching in `Skip`, which was brought up in #80416.
This assumes that if `next` is called, it's likely that there will be more calls to `next`, and the branch for skip will only be hit once thus it's unlikely to take that path. Even w/o the `unlikely` intrinsic, it compiles more efficiently, I believe because the path where `next` is called is always taken.
It should be noted there are very few places in the compiler where `Skip` is used, so probably won't have a noticeable perf impact.
[New impl](https://godbolt.org/z/85rdj4)
[Old impl](https://godbolt.org/z/Wc74rh)
[Some additional asm examples](https://godbolt.org/z/feKzoz) although they really don't have a ton of difference between them.
Expand docs on Iterator::intersperse
Unstable feature in #79524. This expands on the docs to bring them more in line with how other methods of `Iterator` are demonstrated.
Stability oddity with const intrinsics
cc `@RalfJung`
In https://github.com/rust-lang/rust/pull/80699#discussion_r551495670 `@usbalbin` realized we accepted some intrinsics as `const` without a `#[rustc_const_(un)stable]` attribute. I did some digging, and that example works because intrinsics inherit their stability from their parents... including `#[rustc_const_(un)stable]` attributes. While we may want to fix that (not sure, wasn't there just a MCPed PR that caused this on purpose?), we definitely want tests for it, thus this PR adding tests and some fun tracing statements.
Add NonZeroUn::is_power_of_two
This saves instructions on both new and old machines <https://rust.godbolt.org/z/4fjTMz>
- On the default x64 target (with no fancy instructions available) it saves a few instructions by not needing to also check for zero.
- On newer targets (with BMI1) it uses `BLSR` for super-short assembly.
This can be used for things like checks against alignments stored in `NonZeroUsize`.
Add `as_rchunks` (and friends) to slices
`@est31` mentioned (https://github.com/rust-lang/rust/issues/76354#issuecomment-717027175) that, for completeness, there needed to be an `as_chunks`-like method that chunks from the end (with the remainder at the beginning) like `rchunks` does.
So here's a PR for `as_rchunks: &[T] -> (&[T], &[[T; N]])` and `as_rchunks_mut: &mut [T] -> (&mut [T], &mut [[T; N]])`.
But as I was doing this and copy-pasting `from_raw_parts` calls, I thought that I should extract that into an unsafe method. It started out a private helper, but it seemed like `as_chunks_unchecked` could be reasonable as a "real" method, so I added docs and made it public. Let me know if you think it doesn't pull its weight.
Rollup of 17 pull requests
Successful merges:
- #78455 (Introduce {Ref, RefMut}::try_map for optional projections in RefCell)
- #80144 (Remove giant badge in README)
- #80614 (Explain why borrows can't be held across yield point in async blocks)
- #80670 (TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips)
- #80681 (Clarify what the effects of a 'logic error' are)
- #80764 (Re-stabilize Weak::as_ptr and friends for unsized T)
- #80901 (Make `x.py --color always` apply to logging too)
- #80902 (Add a regression test for #76281)
- #80941 (Do not suggest invalid code in pattern with loop)
- #80968 (Stabilize the poll_map feature)
- #80971 (Put all feature gate tests under `feature-gates/`)
- #81021 (Remove doctree::Import)
- #81040 (doctest: Reset errors before dropping the parse session)
- #81060 (Add a regression test for #50041)
- #81065 (codegen_cranelift: Fix redundant semicolon warn)
- #81069 (Add sample code for Rc::new_cyclic)
- #81081 (Add test for #34792)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
TrustedRandomAaccess specialization composes incorrectly for nested iter::Zips
I found this while working on improvements for TRA.
After partially consuming a Zip adapter and then wrapping it into another Zip where the adapters use their `TrustedRandomAccess` specializations leads to the outer adapter returning elements which should have already been consumed.
If the optimizer gets tripped up by the addition this might affect performance for chained `zip()` iterators even when the inner one is not partially advanced but it would require more extensive fixes to `TrustedRandomAccess` to communicate those offsets earlier.
Included test fails on nightly, [playground link](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=24fa1edf8a104ff31f5a24830593b01f)
implement ptr::write without dedicated intrinsic
This makes `ptr::write` more consistent with `ptr::write_unaligned`, `ptr::read`, `ptr::read_unaligned`, all of which are implemented in terms of `copy_nonoverlapping`.
This means we can also remove `move_val_init` implementations in codegen and Miri, and its special handling in the borrow checker.
Also see [this Zulip discussion](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/ptr.3A.3Aread.20vs.20ptr.3A.3Awrite).
Fix formatting specifiers doc links
d36e3e23a8 seems to have inadvertently changed many of these links to point to `core::fmt` instead of `std::fmt`. The information about formatting specifiers is only documented in [`std::fmt`](https://doc.rust-lang.org/std/fmt/); [`core::fmt`](https://doc.rust-lang.org/core/fmt/) is empty. 3baf6a4a74 seems to have already fixed a couple of these links to point back to `std::fmt`.
