Document non-obvious behavior of fmt::UpperHex & co for negative integers
Before stabilization I’d have suggested changing the behavior, but that time is past.
Introduce LinkedList::drain_filter
This introduces `LinkedList::remove_if`.
This operation embodies one of the use-cases where `LinkedList` would typically be preferred over `Vec`: random removal and retrieval.
There are a number of considerations with this:
Should there be two `remove_if` methods? One where elements are only removed, one which returns a collection of removed elements.
Should this be implemented using a draining iterator pattern that covers both cases? I suspect that would incur a bit of overhead (moving the element into the iterator, then into a new collection). But I'm not sure. Maybe that's an acceptable compromise to maximize flexibility.
I don't feel I've had enough exposure to unsafe programming in rust to be certain the implementation is correct. This relies quite heavily on moving around copies of Shared pointers to make the code reasonable. Please help me out :).
Remove semicolon note
In reference to issue #46186
r? @estebank
First time doing a pull request, if there are any suggestions on how to improve this please let me know.
@jjolly
MIR: Fix value moved diagnose messages
#45960. I believe this will take a different approach. Simply replacing all nouns to verbs (`desired_action`) messes up the message `use of moved value` (although fixes the message in original issue). Here is what happens:
<pre>
$ rustc -Zborrowck-mir src/test/ui/borrowck/borrowck-reinit.rs
error[E0382]: <b>used</b> of moved value: `x` (Mir)
--> src/test/ui/borrowck/borrowck-reinit.rs:18:16
|
17 | drop(x);
| - value moved here
18 | let _ = (1,x);
| ^ value used here after move
error: aborting due to 2 previous errors
</pre>
(Notice: *"**used** of moved value: `x`"* instead of *"**use**"*)
Which does not seem to be okay.
After experimenting a bit, it looks like [`report_use_of_moved_value()`](1dc0b573e7/src/librustc_mir/borrow_check.rs (L1319)) tries to handle both these messages by taking in only one form of`desired_action`.
These messages rise from: *"[{noun} of moved value](1dc0b573e7/src/librustc_mir/borrow_check.rs (L1338-L1342))"* and *"[value {verb} here after move](1dc0b573e7/src/librustc_mir/borrow_check.rs (L1343))"*.
This PR fixes *"value {verb} here after move"* type messages by passing a corresponding verb (`desired_action`) instead of the original noun.
Stabilize spin_loop_hint
Stabilize `spin_loop_hint` in release `1.23.0`.
I've also renamed feature `hint_core_should_pause` to `spin_loop_hint`.
cc #41196
Implement From<RecvError> for TryRecvError and RecvTimeoutError
According to the documentation, it looks to me that `TryRecvError` and `RecvTimeoutError` are strict extensions of `RecvError`. As such, it makes sense to allow conversion from the latter type to the two former types without constraining future developments.
This permits to write `input.recv()?` and `input.recv_timeout(timeout)?` in the same function for example.
Mir Borrowck: Parity with Ast for E0384 (Cannot assign twice to immutable)
- Closes#45199
- Don't allow assigning to dropped immutable variables
- Show the "first assignment" note on the first assignment that can actually come before the second assignment.
- Make "first assignment" notes point to function parameters if needed.
- Don't show a "first assignment" note if the first and second assignment have the same span (in a loop). This matches ast borrowck for now, but maybe this we should add "in previous loop iteration" as with some other borrowck errors. (Commit 2)
- Use revisions to check mir borrowck for the existing tests for this error. (Commit 3)
~~Still working on a less ad-hoc way to get 'first assignment' notes to show on the correct assignment. Also need to check mutating function arguments.~~ Now using a new dataflow pass.
Make accesses to fields of packed structs unsafe
To handle packed structs with destructors (which you'll think are a rare
case, but the `#[repr(packed)] struct Packed<T>(T);` pattern is
ever-popular, which requires handling packed structs with destructors to
avoid monomorphization-time errors), drops of subfields of packed
structs should drop a local move of the field instead of the original
one.
That's it, I think I'll use a strategy suggested by @Zoxc, where this mir
```
drop(packed_struct.field)
```
is replaced by
```
tmp0 = packed_struct.field;
drop tmp0
```
cc #27060 - this should deal with that issue after codegen of drop glue
is updated.
The new errors need to be changed to future-compatibility warnings, but
I'll rather do a crater run first with them as errors to assess the
impact.
cc @eddyb
Things which still need to be done for this:
- [ ] - handle `repr(packed)` structs in `derive` the same way I did in `Span`, and use derive there again
- [ ] - implement the "fix packed drops" pass and call it in both the MIR shim and validated MIR pipelines
- [ ] - do a crater run
- [ ] - convert the errors to compatibility warnings
mention nightly in -Z external-macro-backtrace note
Fix#46167 by mentioning that you need nightly in the message that tells you to pass `-Z external-macro-backtrace`.
Rationale:
1. The reason for having this message is to increase discoverability of the functionality. If the message is only shown on nightly it's less disoverable.
2. The same approach is taken if you call a const fn in const context without its feature gate (previously, if you called it without `#![feature(const_fn)]`).
cc @kennytm
Add a MIR-borrowck-only output mode
Removes the `-Z borrowck-mir` flag in favour of a `-Z borrowck=mode` flag where mode can be `mir`, `ast`, or `compare`.
* The `ast` mode represents the current default, passing `-Z borrowck=ast` is equivalent to not passing it at all.
* The `compare` mode outputs both the output of the MIR borrow checker and the AST borrow checker, each error with `(Ast)` and `(Mir)` appended. This mode has the same behaviour as `-Z borrowck-mir` had before this commit.
* The `mir` mode only outputs the results of the MIR borrow checker, while suppressing the errors of the ast borrow checker
The PR also updates the tests to use the new flags.
closes #46097
rustc_trans: don't apply noalias on returned references.
In #45225 frozen returned `&T` were accidentally maked `noalias`, unlike `&mut T`.
Return value `noalias` is only sound for functions that return dynamic allocations, e.g. `Box`, and using it on anything else can lead to miscompilation, as LLVM assumes certain usage patterns.
Fixes#46239.
There's a trailing whitespace problem in one of the tests. @nrc said
he'll go fix it quickly, but until then I'll like to land this PR.
I suspect this happened because one of the dependencies in the
Cargo.lock I updated had changed the format of the XML they emit, but
that has to be investigated.
Fix the derive implementation for repr(packed) structs to move the
fields out instead of calling functions on references to each subfield.
That's it, `#[derive(PartialEq)]` on a packed struct now does:
```Rust
fn eq(&self, other: &Self) {
let field_0 = self.0;
let other_field_0 = other.0;
&field_0 == &other_field_0
}
```
Instead of
```Rust
fn eq(&self, other: &Self) {
let ref field_0 = self.0;
let ref other_field_0 = other.0;
&*field_0 == &*other_field_0
}
```
Taking (unaligned) references to each subfield is undefined, unsound and
is an error with MIR effectck, so it had to be prevented. This causes
a borrowck error when a `repr(packed)` struct has a non-Copy field (and
therefore is a [breaking-change]), but I don't see a sound way to avoid
that error.
