In bluss/indexmap#88, we found that there was no easy way to implement
`Debug` for our `IterMut` and `Drain` iterators. Those are built on
`slice::IterMut` and `vec::Drain`, which implement `Debug` themselves,
but have no other way to access their data. With a new `as_slice()`
method, we can read the data and customize its presentation.
Have all methods of Filter and FilterMap use internal iteration
This PR changes `Filter::{next, next_back, count}` and `FilterMap::{next, next_back}` to all use internal iteration. The `next` and `next_back` methods are changed to directly forward to `try_for_each` and `try_rfold` respectively, using `Result` as the `Try` type. I think that's okay? Alternatively, I could change their implementations to use `LoopState` instead if there's any benefit in doing so.
r? @scottmcm
Stabilize `unrestricted_attribute_tokens`
In accordance with a plan described in https://internals.rust-lang.org/t/unrestricted-attribute-tokens-feature-status/8561/3.
Delimited non-macro non-builtin attributes now support the same syntax as macro attributes:
```
PATH
PATH `(` TOKEN_STREAM `)`
PATH `[` TOKEN_STREAM `]`
PATH `{` TOKEN_STREAM `}`
```
Such attributes mostly serve as inert proc macro helpers or tool attributes.
To some extent these attributes are de-facto stable due to a hole in feature gate checking (feature gating is done too late - after macro expansion.)
So if macro *removes* such helper attributes during expansion (and it must remove them, unless it's a derive macro), then the code will work on stable.
Key-value non-macro non-builtin attributes are now restricted to bare minimum required to support what we support on stable - unsuffixed literals (https://github.com/rust-lang/rust/issues/34981).
```
PATH `=` LITERAL
```
(Key-value macro attributes are not supported at all right now.)
Crater run in https://github.com/rust-lang/rust/pull/57321 found no regressions for this change.
There are multiple possible ways to extend key-value attributes (https://github.com/rust-lang/rust/pull/57321#issuecomment-451574065), but I'd expect an RFC for that and it's not a pressing enough issue to block stabilization of delimited attributes.
Built-in attributes are still restricted to the "classic" meta-item syntax, nothing changes here.
https://github.com/rust-lang/rust/pull/57321 goes further and adds some additional restrictions (more consistent input checking) to built-in attributes.
Closes https://github.com/rust-lang/rust/issues/55208
Turn duration consts into associated consts
As suggested in https://github.com/rust-lang/rust/issues/57391#issuecomment-459658236, I'm moving `Duration` constants (`SECOND`, `MILLISECOND` and so on; currently behind unstable `duration_constants` feature) into the `impl Duration` block.
cc @frewsxcv @SimonSapin
RangeInclusive internal iteration performance improvement.
Specialize `Iterator::try_fold` and `DoubleEndedIterator::try_rfold` to improve code generation in all internal iteration scenarios.
This changes brings the performance of internal iteration with `RangeInclusive` on par with the performance of iteration with `Range`:
- Single conditional jump in hot loop,
- Unrolling and vectorization,
- And even Closed Form substitution.
Unfortunately, it only applies to internal iteration. Despite various attempts at stream-lining the implementation of `next` and `next_back`, LLVM has stubbornly refused to optimize external iteration appropriately, leaving me with a choice between:
- The current implementation, for which Closed Form substitution is performed, but which uses 2 conditional jumps in the hot loop when optimization fail.
- An implementation using a `is_done` boolean, which uses 1 conditional jump in the hot loop when optimization fail, allowing unrolling and vectorization, but for which Closed Form substitution fails.
In the absence of any conclusive evidence as to which usecase matters most, and with no assurance that the lack of Closed Form substitution is not indicative of other optimizations being foiled, there is no way
to pick one implementation over the other, and thus I defer to the statu quo as far as `next` and `next_back` are concerned.
Rollup of 17 pull requests
Successful merges:
- #57656 (Deprecate the unstable Vec::resize_default)
- #58059 (deprecate before_exec in favor of unsafe pre_exec)
- #58064 (override `VecDeque::try_rfold`, also update iterator)
- #58198 (Suggest removing parentheses surrounding lifetimes)
- #58431 (fix overlapping references in BTree)
- #58555 (Add a note about 2018e if someone uses `try {` in 2015e)
- #58588 (remove a bit of dead code)
- #58589 (cleanup macro after 2018 transition)
- #58591 (Dedup a rustdoc diagnostic construction)
- #58600 (fix small documentation typo)
- #58601 (Search for target_triple.json only if builtin target not found)
- #58606 (Docs: put Future trait into spotlight)
- #58607 (Fixes#58586: Make E0505 erronous example fail for the 2018 edition)
- #58615 (miri: explain why we use static alignment in ref-to-place conversion)
- #58620 (introduce benchmarks of BTreeSet.intersection)
- #58621 (Update miri links)
- #58632 (Make std feature list sorted)
Failed merges:
r? @ghost
Docs: put Future trait into spotlight
If a function returns a type that implements `Future`, there should be a small "i" symbol next to it indicating the return type implements an important trait.
improve Pin documentation
Incorporates a bunch of the documentation-related comments that came up when discussing `Pin` stabilization.
Cc @alexcrichton @withoutboats @cramertj @jonhoo
Fixes https://github.com/rust-lang/rust/issues/58130
Make overflowing and wrapping negation const
Remember that the signed and unsigned versions are slightly different here, so there's four functions made const instead of just two.
Fix typo in std::future::Future docs
I am not quite sure if this is actually a typo but
1. to me the sentence doesn't make sense if it says "expect"
2. I hope that `Future`s are not really allowed to cause memory unsafety if they are polled after completion.
