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.

…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 <[email protected]>

This commit fixes a regression introduced in rust-lang#73317 where an oversight
meant that `config.toml` was assumed to exist.

Signed-off-by: David Wood <[email protected]>

…n or propagation

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

Improve compiler error message for wrong generic parameter order

- Added optional "help" parameter that shows a help message on the compiler error if required.
- Added a simple ordered parameter as a sample help.

@varkor will make more changes as required. Let me know if I'm heading in the right direction.

Fixes rust-lang#68437

r? @varkor

…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

…ebank

Show the values and computation that would overflow a const evaluation or propagation

Fixes rust-lang#71134

In contrast to the example in the issue it doesn't use individual spans for each operand. The effort required to implement that is quite high compared to the little (if at all) benefit it would bring to diagnostics.

cc @shepmaster

The way this is implemented it is also fairly easy to do the same for overflow panics at runtime, but that should be done in a separate PR since it may have runtime performance implications.

…s, r=oli-obk

Add second message for LiveDrop errors

This is an attempt to fix rust-lang#72907 by adding a second message to the `LiveDrop` diagnostics. Changing from this
```
error[E0493]: destructors cannot be evaluated at compile-time
 --> src/lib.rs:7:9
  |
7 |     let mut always_returned = None;
  |         ^^^^^^^^^^^^^^^^^^^ constants cannot evaluate destructors

error: aborting due to previous error
```
to this
```
error[E0493]: destructors cannot be evaluated at compile-time
  --> foo.rs:6:9
   |
6  |     let mut always_returned = None;
   |         ^^^^^^^^^^^^^^^^^^^ constants cannot evaluate destructors
...
10 |         always_returned = never_returned;
   |         --------------- value is dropped here

error: aborting due to previous error
```
r? @RalfJung @ecstatic-morse

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

Make is_freeze and is_copy_modulo_regions take TyCtxtAt

Make is_freeze and is_copy_modulo_regions take TyCtxtAt instead of separately taking TyCtxt and Span. This is consistent with is_sized.

switch_ty is redundant

This field is redundant, but we cannot remove it currently as pretty-printing relies on it (and it does not have access to `mir::Body` to compute the type itself).

Cc @oli-obk @matthewjasper @jonas-schievink

…var, r=Mark-Simulacrum

bootstrap: no `config.toml` exists regression

Fixes rust-lang#73574.

This PR fixes a regression introduced in rust-lang#73317 where an oversight meant that `config.toml` was assumed to exist.