We can never supply a meaningful implementation of this.
Instead, the follow up commits will create two intrinsics
that approximate comparisons:

* `ptr_maybe_eq`
* `ptr_maybe_ne`

The fact that `ptr_maybe_eq(a, b)` is not necessarily the same
value as `!ptr_maybe_ne(a, b)` is a symptom of this entire
problem.

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.

…aining everything in the diagnostic

This commit fixes typos in the doc comments of 'librustc_mir/monomorphize/collector.rs'

…int.

typo fix

Co-authored-by: Jonas Schievink <jonasschievink@gmail.com>

This fixes an issue with the following sample:

    mod foo {
	mod inaccessible {
	    pub struct X;
	}
	pub mod avail {
	    pub struct X;
	}
    }

    fn main() { X; }

Instead of suggesting both `use crate::foo::inaccessible::X;` and `use
crate::foo::avail::X;`, it should only suggest the latter.

It is done by trimming the list of suggestions from inaccessible paths
if accessible paths are present.

Visibility is checked with `is_accessible_from` now instead of being
hard-coded.

-

Some tests fixes are trivial, and others require a bit more explaining,
here are my comments:

src/test/ui/issues/issue-35675.stderr: Only needs to make the enum
public to have the suggestion make sense.

src/test/ui/issues/issue-42944.stderr: Importing the tuple struct won't
help because its constructor is not visible, so the attempted
constructor does not work. In that case, it's better not to suggest it.
The case where the constructor is public is covered in `issue-26545.rs`.

Add comment to clarify the pattern

impl PartialEq<Vec<B>> for &[A], &mut [A]

rust-lang/rfcs#2917

add Windows system error codes that should map to io::ErrorKind::TimedOut

closes rust-lang#71646

**Disclaimer:** The author of this pull request has a negligible amount of experience (i.e., kinda zero) with the Windows API. This PR should _definitely_ be reviewed by someone familiar with the API and its error handling.

While porting POSIX software using serial ports to Windows, I found that for many Windows system error codes, an `io::Error` created via `io::Error::from_raw_os_error()` or `io::Error::last_os_error()` is not `io::ErrorKind::TimedOut`. For example, when a (non-overlapped) write to a COM port via [`WriteFile()`](https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-readfile) times out, [`GetLastError()`](https://docs.microsoft.com/en-us/windows/win32/api/errhandlingapi/nf-errhandlingapi-getlasterror) returns `ERROR_SEM_TIMEOUT` ([121](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-)). However, an `io::Error` created from this error code will have `io::ErrorKind::Other`.

Currently, only the error codes `ERROR_OPERATION_ABORTED` and `WSAETIMEDOUT` will instantiate `io::Error`s with kind `io::ErrorKind::TimedOut`.
This makes `io::Error::last_os_error()` unsuitable for error handling of syscalls that could time out, because timeouts can not be caught by matching the error's kind against `io::ErrorKind::TimedOut`.

Downloading the [list of Windows system error codes](https://gist.github.com/carstenandrich/c331d557520b8a0e7f44689ca257f805) and grepping anything that sounds like a timeout (`egrep -i "timed?.?(out|limit)"`), I've identified the following error codes that should also have `io::ErrorKind::TimedOut`, because they could be I/O-related:

Name | Code | Description
--- | --- | ---
`ERROR_SEM_TIMEOUT` | [121](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-) | The semaphore timeout period has expired.
`WAIT_TIMEOUT` | [258](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--0-499-) | The wait operation timed out.
`ERROR_DRIVER_CANCEL_TIMEOUT` | [594](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--500-999-) | The driver %hs failed to complete a cancelled I/O request in the allotted time.
`ERROR_COUNTER_TIMEOUT` | [1121](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--1000-1299-) | A serial I/O operation completed because the timeout period expired. The IOCTL_SERIAL_XOFF_COUNTER did not reach zero.)
`ERROR_TIMEOUT` | [1460](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--1300-1699-) | This operation returned because the timeout period expired.
`ERROR_CTX_MODEM_RESPONSE_TIMEOUT` | [7012](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--6000-8199-) | The modem did not respond to the command sent to it. Verify that the modem is properly cabled and powered on.
`ERROR_CTX_CLIENT_QUERY_TIMEOUT` | [7040](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--6000-8199-) | The client failed to respond to the server connect message.
`ERROR_DS_TIMELIMIT_EXCEEDED` | [8226](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--8200-8999-) | The time limit for this request was exceeded.
`DNS_ERROR_RECORD_TIMED_OUT` | [9705](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--9000-11999-) | DNS record timed out.
`ERROR_IPSEC_IKE_TIMED_OUT` | [13805](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--12000-15999-) | Negotiation timed out.

The following errors are also timeouts, but they don't seem to be directly related to I/O or network operations:

Name | Code | Description
--- | --- | ---
`ERROR_SERVICE_REQUEST_TIMEOUT` | [1053](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--1000-1299-) | The service did not respond to the start or control request in a timely fashion.
`ERROR_RESOURCE_CALL_TIMED_OUT` | [5910](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--4000-5999-) | The call to the cluster resource DLL timed out.
`FRS_ERR_SYSVOL_POPULATE_TIMEOUT` | [8014](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--6000-8199-) | The file replication service cannot populate the system volume because of an internal timeout. The event log may have more information.
`ERROR_RUNLEVEL_SWITCH_TIMEOUT` | [15402](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--12000-15999-) | The requested run level switch cannot be completed successfully since one or more services will not stop or restart within the specified timeout.
`ERROR_RUNLEVEL_SWITCH_AGENT_TIMEOUT` | [15403](https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes--12000-15999-) | A run level switch agent did not respond within the specified timeout.

Please note that `ERROR_SEM_TIMEOUT` is the only timeout error I have [seen in action](https://gist.github.com/carstenandrich/10b3962fa1abc9e50816b6460010900b). The remainder of the error codes listed above is based purely on reading documentation.

This pull request adds all of the errors listed in both tables, but I'm not sure whether adding all of them makes sense. Someone with actual Windows API experience should decide that.

I expect these changes to be fairly backwards compatible, because only the error's [`.kind()`](https://doc.rust-lang.org/std/io/struct.Error.html#method.kind) will change, but matching the error's code via [`.raw_os_error()`](https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error) will not be affected.
However, code expecting these errors to be `io::ErrorKind::Other` would break. Even though I personally do not think such an implementation would make sense, after all the docs say that `io::ErrorKind` is _intended to grow over time_, a residual risk remains, of course. I took the liberty to ammend the docstring of `io::ErrorKind::Other` with a remark that discourages matching against it.

As per the contributing guidelines I'm adding @steveklabnik due to the changed documentation. Also @retep998 might have some valuable insights on the error codes.

r? @steveklabnik
cc @retep998
cc @Mark-Simulacrum

…rochenkov

Prefer accessible paths in 'use' suggestions

This PR addresses issue rust-lang#26454, where `use` suggestions are made for paths that don't work. For example:

```rust
mod foo {
    mod bar {
        struct X;
    }
}

fn main() { X; } // suggests `use foo::bar::X;`
```

…eck, r=ollie27

Enforce doc alias check

Part of rust-lang#50146.

r? @ollie27

…,RalfJung,nagisa

A way forward for pointer equality in const eval

r? @varkor on the first commit and @RalfJung on the second commit

cc rust-lang#53020

…an-DPC

Clean up E0689 explanation

r? @Dylan-DPC

Add E0765

…tthewjasper

Provide suggestions for some moved value errors

When encountering an used moved value where the previous move happened
in a `match` or `if let` pattern, suggest using `ref`. Fix rust-lang#63988.

When encountering a `&mut` value that is used in multiple iterations of
a loop, suggest reborrowing it with `&mut *`. Fix rust-lang#62112.

Fix typos in doc comments

Hello 🦀 ,

This commit fixes typos in the doc comments of 'librustc_mir/monomorphize/collector.rs'

Thank you for reviewing this PR 👍

…hewjasper

Fix typo in error_codes doc

…from, r=Amanieu

deprecate wrapping_offset_from

As per rust-lang#41079 (comment) which seems like a consensus.

r? @Amanieu

Miri: replace many bug! by span_bug!

r? @oli-obk

…ulacrum

Do not send a notification for P-high stable regressions

This is kind of a hack to only match nightly and beta regressions, but not stable regressions. See my tests [on the playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=6ff8a809162118aa2951f2ff12400067).

r? @spastorino cc @Mark-Simulacrum