Provide `{to,from}_{ne,le,be}_bytes` functions on integers
If one doesn't view integers as containers of bytes, converting them to
bytes necessarily needs the specfication of encoding.
I think Rust is a language that wants to be explicit. The `to_bytes`
function is basically the opposite of that – it converts an integer into
the native byte representation, but there's no mention (in the function
name) of it being very much platform dependent. Therefore, I think it
would be better to replace that method by three methods, the explicit
`to_ne_bytes` ("native endian") which does the same thing and
`to_{le,be}_bytes` which return the little- resp. big-endian encoding.
If one doesn't view integers as containers of bytes, converting them to
bytes necessarily needs the specfication of encoding.
I think Rust is a language that wants to be explicit. The `to_bytes`
function is basically the opposite of that – it converts an integer into
the native byte representation, but there's no mention (in the function
name) of it being very much platform dependent. Therefore, I think it
would be better to replace that method by three methods, the explicit
`to_ne_bytes` ("native endian") which does the same thing and
`to_{le,be}_bytes` which return the little- resp. big-endian encoding.
slices: fix ZST slice iterators making up pointers; debug_assert alignment in from_raw_parts
This fixes the problem that we are fabricating pointers out of thin air. I also managed to share more code between the mutable and shared iterators, while reducing the amount of macros.
I am not sure how useful it really is to add a `debug_assert!` in libcore. Everybody gets a release version of that anyway, right? Is there at least a CI job that runs the test suite with a debug version?
Fixes#42789
Rollup of 15 pull requests
Successful merges:
- #52793 (Add test for NLL: unexpected "free region `` does not outlive" error )
- #52799 (Use BitVector for global sets of AttrId)
- #52809 (Add test for unexpected region for local data ReStatic)
- #52834 ([NLL] Allow conflicting borrows of promoted length zero arrays)
- #52835 (Fix Alias intra doc ICE)
- #52854 (fix memrchr in miri)
- #52899 (tests/ui: Add missing mips{64} ignores)
- #52908 (Use SetLenOnDrop in Vec::truncate())
- #52915 (Don't count MIR locals as borrowed after StorageDead when finding locals live across a yield terminator)
- #52926 (rustc: Trim down the `rust_2018_idioms` lint group)
- #52930 (rustc_resolve: record single-segment extern crate import resolutions.)
- #52939 (Make io::Read::read_to_end consider io::Take::limit)
- #52942 (Another SmallVec.extend optimization)
- #52947 (1.27 actually added the `armv5te-unknown-linux-musleabi` target)
- #52954 (async can begin expressions)
Failed merges:
r? @ghost
fix memrchr in miri
The previous PR https://github.com/rust-lang/rust/pull/52744 was not enough because it assumed that the split between the `mid` and `end` parts returned by `align_to` was aligned. But really the only guarantee we have is that the `mid` part is aligned, so make use of that.
Fix From<LocalWaker>
This is a follow-up to https://github.com/rust-lang/rust/pull/52640
Fixes `From<LocalWaker>` which is affected by the same accidental drop bug (unless I'm totally mistaken)
r? @cramertj
Rollup of bare_trait_objects PRs
All deny attributes were moved into bootstrap so they can be disabled with a line of config.
Warnings for external tools are allowed and it's up to the tool's maintainer to keep it warnings free.
r? @Mark-Simulacrum
cc @ljedrz @kennytm
std::ops::Try impl for std::task::Poll
I originally left out the `Try` impl for `Poll` because I was curious if we needed it, and @MajorBreakfast and I had discussed the potential for it to introduce confusion about exactly what control-flow was happening at different points. However, after porting a pretty significant chunk of Fuchsia over to futures 0.3, I discovered that I was *constantly* having to do repetitive matching on `Poll<Result<...>>` or `Poll<Option<Result<...>>>` in order to propagate errors correctly. `try_poll` (propagate `Poll::Ready(Err(..))`s) helped in some places, but it was far more common to need some form of conversion between `Result`, `Poll<Result<...>>`, and `Poll<Option<Result<...>>>`. The `Try` trait conveniently provides all of these conversions in addition to a more concise syntax (`?`), so I'd like to experiment with using these instead.
cc @seanmonstar
r? @aturon
Note: this change means that far more futures 0.1 code can work without significant changes since it papers over the fact that `Result` is no longer at the top-level when using `Stream` and `Future` (since it's now `Poll<Result<...>>` or `Poll<Option<Result<...>>>` instead of `Result<Poll<..>>` and `Result<Poll<Option<...>>>`).
Clarify what a task is
Currently we call two distinct concepts "task":
1. The top-level future that is polled until completion
2. The lightweight "thread" that is responsible for polling the top-level future. What additional data beside the future is stored in this type varies between different `Executor` implementations.
I'd prefer to return to the old formulation by @alexcrichton:
```rust
/// A handle to a "task", which represents a single lightweight "thread" of
/// execution driving a future to completion.
pub struct Task {
```
Source: [`task_impl/mod.rs` in futures-rs 0.1](1328fc9e8a/src/task_impl/mod.rs (L49-L50))
I think that this change will make it much easier to explain everything.
r? @aturon
@cramertj
