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FabianWolff and others added 19 commits May 7, 2021 20:46
This warning always referenced panic! even in case of an
assert. Related to rust-lang#84656
Signed-off-by: Ian Jackson <[email protected]>
Co-authored-by: Mara Bos <[email protected]>
Fix suggestions for missing return type lifetime specifiers

This pull request aims to fix rust-lang#84592. The issue is that the current code seems to assume that there is only a single relevant span pointing to the missing lifetime, and only looks at the first one:
https://github.com/rust-lang/rust/blob/e5f83d24aee866a14753a7cedbb4e301dfe5bef5/compiler/rustc_resolve/src/late/lifetimes.rs#L2959

This is incorrect, though, and leads to incorrect error messages and invalid suggestions. For instance, the example from rust-lang#84592:
```rust
struct TwoLifetimes<'x, 'y> {
    x: &'x (),
    y: &'y (),
}

fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
    TwoLifetimes { x: &(), y: &() }
}
```
currently leads to:
```
error[E0106]: missing lifetime specifiers
 --> src/main.rs:6:57
  |
6 | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
  |                            ---     ---                  ^^ expected 2 lifetime parameters
  |
  = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
help: consider introducing a named lifetime parameter
  |
6 | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'_<'a, 'a>, '_> {
  |                        ^^^^    ^^^^^^     ^^^^^^                  ^^^^^^^^^^
```
There are two problems:
- The error message is wrong. There is only _one_ lifetime parameter expected at the location pointed to by the error message (and another one at a separate location).
- The suggestion is incorrect and will not lead to correct code.

With the changes in this PR, I get the following output:
```
error[E0106]: missing lifetime specifiers
 --> p.rs:6:57
  |
6 | fn two_lifetimes_needed(a: &(), b: &()) -> TwoLifetimes<'_, '_> {
  |                            ---     ---                  ^^  ^^ expected named lifetime parameter
  |                                                         |
  |                                                         expected named lifetime parameter
  |
  = help: this function's return type contains a borrowed value, but the signature does not say whether it is borrowed from `a` or `b`
help: consider introducing a named lifetime parameter
  |
6 | fn two_lifetimes_needed<'a>(a: &'a (), b: &'a ()) -> TwoLifetimes<'a, 'a> {
  |                        ^^^^    ^^^^^^     ^^^^^^                  ^^  ^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0106`.
```
Mainly, I changed `add_missing_lifetime_specifiers_label()` to receive a _vector_ of spans (and counts) instead of just one, and adjusted its body accordingly.
Improve "panic message is not a string literal" warning

This warning always referenced panic! even in case of an
assert. Related to rust-lang#84656
Make unchecked_{add,sub,mul} inherent methods unstably const

The intrinsics are marked as being stably const (even though they're not stable by nature of being intrinsics), but the currently-unstable inherent versions are not marked as const. This fixes this inconsistency. Split out of rust-lang#85017,

r? `@oli-obk`
ensure failing promoteds in const/static bodies are handled correctly

`const`/`static` bodies are the one case where we still promote code that might fail to evaluate. Ensure that this is handled correctly; in particular, it must not fail compilation.

`src/test/ui/consts/const-eval/erroneous-const.rs` ensures that when a non-promoted fails to evaluate, we *do* show an error.

r? `@oli-obk`
Provide io::Seek::rewind

Using `Seek::seek` is slightly clumsy because of the need to write (or import) `std::io::SeekFrom` to get at `SeekStart`.  C already has `rewind` (although with broken error handling); we should have it too.

I'm motivated to do this because I've just found myself copy-pasting my 5-line extension trait between projects.

That the example ends up using `OpenOptions` makes this look like a niche use case, but it is very common to rewind temporary files.  `tempfile` isn't available for use in this example or it would have looked shorter and more natural.

If this gets a positive reception I will open a tracking issue and update the feature gate.
@rustbot rustbot added the rollup A PR which is a rollup label May 10, 2021
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@bors r+ rollup=never p=5

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bors commented May 10, 2021

📌 Commit e763401 has been approved by Dylan-DPC

@bors bors added the S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. label May 10, 2021
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bors commented May 10, 2021

⌛ Testing commit e763401 with merge 266f452...

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bors commented May 10, 2021

☀️ Test successful - checks-actions
Approved by: Dylan-DPC
Pushing 266f452 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label May 10, 2021
@bors bors merged commit 266f452 into rust-lang:master May 10, 2021
@rustbot rustbot added this to the 1.54.0 milestone May 10, 2021
@Dylan-DPC-zz Dylan-DPC-zz deleted the rollup-q26gbx3 branch May 10, 2021 21:26
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