Rollup of bare_trait_objects PRs
All deny attributes were moved into bootstrap so they can be disabled with a line of config.
Warnings for external tools are allowed and it's up to the tool's maintainer to keep it warnings free.
r? @Mark-Simulacrum
cc @ljedrz @kennytm
Implement always-fallible TryFrom for usize/isize conversions that are infallible on some platforms
This reverts commit 837d6c7023 "Remove TryFrom impls that might become conditionally-infallible with a portability lint".
This fixes#49415 by adding (restoring) missing `TryFrom` impls for integer conversions to or from `usize` or `isize`, by making them always fallible at the type system level (that is, with `Error=TryFromIntError`) even though they happen to be infallible on some platforms (for some values of `size_of::<usize>()`).
They had been removed to allow the possibility to conditionally having some of them be infallible `From` impls instead, depending on the platforms, and have the [portability lint](https://github.com/rust-lang/rfcs/pull/1868) warn when they are used in code that is not already opting into non-portability. For example `#[allow(some_lint)] usize::from(x: u64)` would be valid on code that only targets 64-bit platforms.
This PR gives up on this possiblity for two reasons:
* Based on discussion with @aturon, it seems that the portability lint is not happening any time soon. It’s better to have the conversions be available *at all* than keep blocking them for so long. Portability-lint-gated platform-specific APIs can always be added separately later.
* For code that is fine with fallibility, the alternative would force it to opt into "non-portability" even though there would be no real portability issue.
Add some performance guidance to std::fs and std::io docs
Adds more documentation about performance to various "read" functions in `fs` and `io`, and to `BufReader`/`BufWriter`, with the goal of helping developers choose the best option for a given task.
Remove "empty buffer" doc in read_until
This appears copied from fill_buf, but the above paragraph already indicates that a lack of delimiter at the end is EOF.
On MIPS, error number 98 is not EADDRINUSE (it is EPROTOTYPE). To fix the
resulting test failure this causes, use a more portable error number in
the example documentation. EINVAL shold be more reliable because it was
defined in the original Unix as 22 so hopefully most derivatives have
defined it the same way.
Better Debug impl for io::Error.
This PR includes the below changes:
1. The former impl wrapped the entire thing in `Error { repr: ... }` which was unhelpful; this has been removed.
2. The `Os` variant of `io::Error` included the code and message, but not the kind; this has been fixed.
3. The `Custom` variant of `io::Error` included a `Custom(Custom { ... })`, which is now just `Custom { ... }`.
Example of previous impl:
```rust
Error {
repr: Custom(
Custom {
kind: InvalidData,
error: Error {
repr: Os {
code: 2,
message: "no such file or directory"
}
}
}
)
}
```
Example of new impl:
```rust
Custom {
kind: InvalidData,
error: Os {
code: 2,
kind: NotFound,
message: "no such file or directory"
}
}
```
