suggest `slice::swap` for `mem::swap(&mut x[0], &mut x[1])` borrowck error
Recently saw someone ask why this code (example slightly modified):
```rs
fn main() {
let mut foo = [1, 2];
std::mem::swap(&mut foo[0], &mut foo[1]);
}
```
triggers this error and how to fix it:
```
error[E0499]: cannot borrow `foo[_]` as mutable more than once at a time
--> src/main.rs:4:33
|
4 | std::mem::swap(&mut foo[0], &mut foo[1]);
| -------------- ----------- ^^^^^^^^^^^ second mutable borrow occurs here
| | |
| | first mutable borrow occurs here
| first borrow later used by call
|
= help: consider using `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices
```
The current help message is nice and goes in the right direction, but I think we can do better for this specific instance and suggest `slice::swap`, which makes this compile
tweak "make mut" spans when assigning to locals
Work towards fixing #106857
This PR just cleans up a lot of spans which is helpful before properly fixing the issues. Best reviewed commit-by-commit.
r? `@estebank`
Tweak borrow suggestion span
Avoids a `span_to_snippet` call when we don't need to surround the expression in parentheses. The fact that the suggestion was using the whole span of the expression rather than just appending a `&` was prevented me from using `// run-rustfix` in another PR (https://github.com/rust-lang/rust/pull/110432#discussion_r1170500484).
Also some drive-by renames of functions that have been annoying me for a bit.
Fix some suggestions where a `Box<T>` is expected.
This fixes#111011, and also adds a suggestion for boxing a unit type when a `Box<T>` was expected and an empty block was found.
Implement tuple<->array convertions via `From`
This PR adds the following impls that convert between homogeneous tuples and arrays of the corresponding lengths:
```rust
impl<T> From<[T; 1]> for (T,) { ... }
impl<T> From<[T; 2]> for (T, T) { ... }
/* ... */
impl<T> From<[T; 12]> for (T, T, T, T, T, T, T, T, T, T, T, T) { ... }
impl<T> From<(T,)> for [T; 1] { ... }
impl<T> From<(T, T)> for [T; 2] { ... }
/* ... */
impl<T> From<(T, T, T, T, T, T, T, T, T, T, T, T)> for [T; 12] { ... }
```
IMO these are quite uncontroversial but note that they are, just like any other trait impls, insta-stable.
My type ascription
Oh rip it out
Ah
If you think we live too much then
You can sacrifice diagnostics
Don't mix your garbage
Into my syntax
So many weird hacks keep diagnostics alive
Yet I don't even step outside
So many bad diagnostics keep tyasc alive
Yet tyasc doesn't even bother to survive!
Tweak await span to not contain dot
Fixes a discrepancy between method calls and await expressions where the latter are desugared to have a span that *contains* the dot (i.e. `.await`) but method call identifiers don't contain the dot. This leads to weird suggestions suggestions in borrowck -- see linked issue.
Fixes#110761
This mostly touches a bunch of tests to tighten their `await` span.
fix false negative for `unused_mut`
fixes https://github.com/rust-lang/rust/issues/110849
We want to avoid double diagnostics for code like this, but only if an error actually occurs:
```rust
fn main() {
let mut x: (i32, i32);
x.0 = 1;
}
```
The first commit fixes the lint and the second one removes all the unused `mut`s it found.
Substitute missing trait items suggestion correctly
Properly substitute missing item suggestions, so that when they reference generics from their parent trait they actually have the right time for the impl.
Also, some other minor tweaks like using `/* Type */` to signify a GAT's type is actually missing, and fixing generic arg suggestions for GATs in general.
Support AIX-style archive type
Reading facility of AIX big archive has been supported by `object` since 0.30.0.
Writing facility of AIX big archive has already been supported by `ar_archive_writer`, but we need to bump the version to support the new archive type enum.
