Fix wrong statement in compare_exchange doc
The documentation for `core::sync::atomic::AtomicSomething::compare_exchange` contains a wrong, or imprecise, statement about the return value. It goes:
The return value is a result indicating whether the new value was written and containing
the previous value. On success this value is guaranteed to be equal to `new`.
In the second sentence, `this value` is gramatically understood as referring to `return value` from the first sentence. Due to how CAS works, the returned value is always what was in the atomic variable _before_ the operation occurred, not what was written into it during the operation. Hence, the fixed doc should say:
The return value is a result indicating whether the new value was written and containing
the previous value. On success this value is guaranteed to be equal to `current`.
This version is confirmed by the runnable examples in variants of `AtomicSomething`, e.g.
assert_eq!(some_bool.compare_exchange(true, false, Ordering::Acquire, Ordering::Relaxed),
Ok(true));
where the returned value is `Ok(current)`. This PR fixes all occurrences of this bug I could find.
An alternative solution would be to modify the second sentence so that it refers to the value _written_ into the Atomic rather than what was there before, in which case it would be correct. Example alternative formulation:
On success the value written into the `bool`/`usize`/`whatever` is guaranteed to be equal to `new`.
r? @steveklabnik
Improvements to pattern resolution + some refactoring
Continuation of https://github.com/rust-lang/rust/pull/33929
First commit is a careful rewrite of `resolve_pattern`, pattern path resolution and new binding creation logic is factored out in separate functions, some minor bugs are fixed. Also, `resolve_possibly_assoc_item` doesn't swallow modules now.
Later commits are refactorings, see the comment descriptions.
I intend to continue this work later with better support for `Def::Err` in patterns in post-resolve stages and cleanup of pattern resolution code in type checker.
Fixes https://github.com/rust-lang/rust/issues/32086
Fixes https://github.com/rust-lang/rust/issues/34047 ([breaking-change])
Fixes https://github.com/rust-lang/rust/issues/34074
cc @jseyfried
r? @eddyb
MIR cleanups and predecessor cache
This PR cleans up a few things in MIR and adds a predecessor cache to allow graph algorithms to be run easily.
r? @nikomatsakis
Rewrote "How Safe and Unsafe Interact" Nomicon chapter.
The previous version of the chapter covered a lot of ground, but was a little meandering and hard to follow at times. This draft is intended to be clearer and more direct, while still providing the same information as the previous version.
r? @steveklabnik
Use it instead of a `panic` for inexhaustive matches and correct the
comment. I think we trust our match-generation algorithm enough to
generate these blocks, and not generating an `unreachable` means that
LLVM won't optimize `match void() {}` to an `unreachable`.
Fix issue #34101
Fix issue #34101: do not track subcontent of type with dtor nor gather flags for untracked content.
(Includes a regression test, which needed to go into `compile-fail/`
due to weaknesses when combining `#[deny(warnings)]` with
`tcx.sess.span_warn(..)`)
Refactor away the prelude injection fold
Instead, just inject `#[prelude_import] use [core|std]::prelude::v1::*;` at the crate root while injecting `extern crate [core|std];` and process `#[no_implicit_prelude]` attributes in `resolve`.
r? @nrc
Support `#[macro_use]` on macro-expanded crates
This PR loads macros from `#[macro_use]` crates during expansion so that
- macro-expanded `#[macro_use]` crates work (fixes#33936, fixes#28071), and
- macros imported from crates have the same scope as macros imported from modules.
This is a [breaking-change]. For example, this will break:
```rust
macro_rules! m {
() => { #[macro_use(foo)] extern crate core; } //~ ERROR imported macro not found
}
m!();
```
Also, this will break:
```rust
macro_rules! try { () => {} }
// #[macro_use] mod bar { macro_rules! try { ... } } //< ... just like this would ...
fn main() { try!(); } //< ... making this an error
```
r? @nrc
trans: don't misuse C_nil for ZSTs other than ().
`C_nil` is actually `C_null` for `()` so `TempRef::new_operand` was treating all ZSTs as `()`.
This should allow running Servo with `RUSTFLAGS=-Zorbit`, assuming there are no other bugs.
