Rollup of 8 pull requests #92925
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Rollup of 8 pull requests #92925
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And to remove possibility of panics while changing the panic handler, because that resulted in a double panic.
Useful for thin wrapper attributes that are best passed as value instead of reference.
…ng projection holds
This hack was added in 6ab1f05. I don't know what change allowed removing the hack, but that commit added a test (which I presume covered the hack's behavior), and all tests are passing with this change. So, I think it should be good.
Inherent associated types *are* supported, just unstable.
This currently calls `std` a "crate" in one part of the message and a "module" in another part. The next commits fix this so it says "crate" in both places.
This allows simplifying a lot of code. It also fixes a subtle bug, exemplified by the test output changes.
Now that `res` is used directly, it seems the conditional is unnecessary.
I'm still not sure why this hack works so seemingly well.
These closures were quite complex and part of a quite complex function. The fact that they are closures makes mistakes likely when refactoring. For example, earlier, I meant to use `resolved`, an argument of the closure, but I instead typed `res`, which captured a local variable and caused a subtle bug that led to a confusing test failure. Extracting them as functions makes the code easier to understand and refactor.
includes minor refactorings
Point at correct argument when async fn output type lifetime disagrees with signature Fixes most of rust-lang#74256. ## Problems fixed This PR fixes a couple of related problems in the error reporting code. ### Highlighting the wrong argument First, the error reporting code was looking at the desugared return type of an `async fn` to decide which parameter to highlight. For example, a function like ```rust async fn async_fn(self: &Struct, f: &u32) -> &u32 { f } ``` desugars to ```rust async fn async_fn<'a, 'b>(self: &'a Struct, f: &'b u32) -> impl Future<Output = &'a u32> + 'a + 'b { f } ``` Since `f: &'b u32` is returned but the output type is `&'a u32`, the error would occur when checking that `'a: 'b`. The reporting code would look to see if the "offending" lifetime `'b` was included in the return type, and because the code was looking at the desugared future type, it was included. So it defaulted to reporting that the source of the other lifetime `'a` (the `self` type) was the problem, when it was really the type of `f`. (Note that if it had chosen instead to look at `'a` first, it too would have been included in the output type, and it would have arbitrarily reported the error (correctly this time) on the type of `f`.) Looking at the actual future type isn't useful for this reason; it captures all input lifetimes. Using the written return type for `async fn` solves this problem and results in less confusing error messages for the user. This isn't a perfect fix, unfortunately; writing the "manually desugared" form of the above function still results in the wrong parameter being highlighted. Looking at the output type of every `impl Future` return type doesn't feel like a very principled approach, though it might work. The problem would remain for function signatures that look like the desugared one above but use different traits. There may be deeper changes required to pinpoint which part of each type is conflicting. ### Lying about await point capture causing lifetime conflicts The second issue fixed by this PR is the unnecessary complexity in `try_report_anon_anon_conflict`. It turns out that the root cause I suggested in rust-lang#76547 (comment) wasn't really the root cause. Adding special handling to report that a variable was captured over an await point only made the error messages less correct and pointed to a problem other than the one that actually occurred. Given the above discussion, it's easy to see why: `async fn`s capture all input lifetimes in their return type, so holding an argument across an await point should never cause a lifetime conflict! Removing the special handling simplified the code and improved the error messages (though they still aren't very good!) ## Future work * Fix error reporting on the "desugared" form of this code * Get the `suggest_adding_lifetime_params` suggestion firing on these examples * cc rust-lang#42703, I think r? `@estebank`
Implement `panic::update_hook`
Add a new function `panic::update_hook` to allow creating panic hooks that forward the call to the previously set panic hook, without race conditions. It works by taking a closure that transforms the old panic hook into a new one, while ensuring that during the execution of the closure no other thread can modify the panic hook. This is a small function so I hope it can be discussed here without a formal RFC, however if you prefer I can write one.
Consider the following example:
```rust
let prev = panic::take_hook();
panic::set_hook(Box::new(move |info| {
println!("panic handler A");
prev(info);
}));
```
This is a common pattern in libraries that need to do something in case of panic: log panic to a file, record code coverage, send panic message to a monitoring service, print custom message with link to github to open a new issue, etc. However it is impossible to avoid race conditions with the current API, because two threads can execute in this order:
* Thread A calls `panic::take_hook()`
* Thread B calls `panic::take_hook()`
* Thread A calls `panic::set_hook()`
* Thread B calls `panic::set_hook()`
And the result is that the original panic hook has been lost, as well as the panic hook set by thread A. The resulting panic hook will be the one set by thread B, which forwards to the default panic hook. This is not considered a big issue because the panic handler setup is usually run during initialization code, probably before spawning any other threads.
Using the new `panic::update_hook` function, this race condition is impossible, and the result will be either `A, B, original` or `B, A, original`.
```rust
panic::update_hook(|prev| {
Box::new(move |info| {
println!("panic handler A");
prev(info);
})
});
```
I found one real world use case here: https://github.com/dtolnay/proc-macro2/blob/988cf403e741aadfd5340bbf67e35e1062a526aa/src/detection.rs#L32 the workaround is to detect the race condition and panic in that case.
The pattern of `take_hook` + `set_hook` is very common, you can see some examples in this pull request, so I think it's natural to have a function that combines them both. Also using `update_hook` instead of `take_hook` + `set_hook` reduces the number of calls to `HOOK_LOCK.write()` from 2 to 1, but I don't expect this to make any difference in performance.
### Unresolved questions:
* `panic::update_hook` takes a closure, if that closure panics the error message is "panicked while processing panic" which is not nice. This is a consequence of holding the `HOOK_LOCK` while executing the closure. Could be avoided using `catch_unwind`?
* Reimplement `panic::set_hook` as `panic::update_hook(|_prev| hook)`?
…arth rustdoc: Yet more intra-doc links cleanup r? `@Manishearth`
feat: rustc_pass_by_value lint attribute Useful for thin wrapper attributes that are best passed as value instead of reference. Fixes rust-lang#76935
Include Projections when elaborating TypeOutlives Fixes rust-lang#92280 In `Elaborator`, we elaborate that `Foo<<Bar as Baz>::Assoc>: 'a` -> `<Bar as Baz>::Assoc: 'a`. This is the same rule that would be applied to any other `Param`. If there are escaping vars, we continue to do nothing. r? `@nikomatsakis`
…cs, r=camelid rustdoc: fix intra-link for generic trait impls fixes rust-lang#92662 r? `@camelid`
…ron1011 Remove some unnecessary uses of `FieldDef::ident` Followup from rust-lang#92533. cc `@Aaron1011` `@petrochenkov`
rustdoc: remove hand-rolled isatty This PR replaces bindings to the platform-specific isatty APIs with the `isatty` crate, as done elsewhere in the repository.
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Successful merges:
panic::update_hook#92598 (Implementpanic::update_hook)FieldDef::ident#92799 (Remove some unnecessary uses ofFieldDef::ident)Failed merges:
r? @ghost
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