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.
This avoids each tool having to separately find and call
`self_profile_alloc_strings`.
- Don't compute the global context if it hasn't yet been computed
This avoids giving extraneous errors about unresolved names if an error
occurs during parsing.
avoid promoting division, modulo and indexing operations that could fail
For division, `x / y` will still be promoted if `y` is a non-zero integer literal; however, `1/(1+1)` will not be promoted any more.
While at it, also see if we can reject promoting floating-point arithmetic (which are [complicated](https://github.com/rust-lang/unsafe-code-guidelines/issues/237) so maybe we should not promote them).
This will need a crater run to see if there's code out there that relies on these things being promoted.
If we can land this, promoteds in `fn`/`const fn` cannot fail to evaluate any more, which should let us do some simplifications in codegen/Miri!
Cc https://github.com/rust-lang/rfcs/pull/3027
Fixes https://github.com/rust-lang/rust/issues/61821
r? `@oli-obk`
Abi::ScalarPair is only ever used for types that don't have a stable
layout anyway so this doesn't break any FFI. It does however reduce the
amount of special casing on the abi outside of the code responsible for
abi specific adjustments to the pass mode.
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.
Improve diagnostics when parsing angle args
https://github.com/rust-lang/rust/pull/79266 introduced parsing of generic arguments in associated type constraints, this however resulted in possibly very confusing error messages in cases in which closing angle brackets were missing such as in `Vec<(u32, _, _) = vec![]`, which outputs an incorrectly parsed equality constraint error, as noted by `@cynecx.`
This PR tries to provide better error messages in such cases.
r? `@petrochenkov`
Refactor token collection to capture trailing token immediately
Split out from https://github.com/rust-lang/rust/pull/80689 - when we start capturing more information about attribute targets, we'll need to know in advance if we're capturing a trailing token or not.
r? `@ghost`
