The old struct tail functions did not deal with `<T as Trait>::A` and `impl
Trait`, at least not explicitly. (We didn't notice this bug before because it
is only exposed when the tail (post deep normalization) is not `Sized`, so it
was a rare case to deal with.)
For post type-checking (i.e. during codegen), there is now
`struct_tail_erasing_lifetimes` and `struct_lockstep_tails_erasing_lifetimes`,
which each take an additional `ParamEnv` argument to drive normalization.
For pre type-checking cases where normalization is not needed, there is
`struct_tail_without_normalization`. (Currently, the only instance of this is
`Expectation::rvalue_hint`.)
All of these new entrypoints work by calling out to common helper routines.
The helpers are parameterized over a closure that handles the normalization.
Update cargo-vendor usage
This contains a variety of updates to clean up the usage of cargo-vendor.
- Remove the install step for the old cargo-vendor now that it is built-in to cargo and available in the stage0 install.
- Update installation instructions, dealing with vendoring. The current instructions of running `sudo ./x.py install` is broken, it will almost always fail (since the vendor directory doesn't exist). Since the steps for properly handling this are numerous, I'm recommending removing the suggestion to use `sudo` altogether.
- If the sudo-forced-vendoring detects that the vendor directory is not available, abort with instructions on how to fix.
- Now that cargo-vendor is built-in, automatically run it if it looks like it is needed.
- Update instructions on how to install cargo.
- Remove the unused markdown link references in README/CONTRIBUTING. This reverts most of #44935. These references don't do anything if they are unused.
Closes#49269
cc #61142#48771#40108
Remove rustc_mir dependency from rustc_borrowck
Also renames `rustc_borrowck` to `rustc_ast_borrowck` and removes all error reporting from it.
cc #59193
filedesc: don't use ioctl(FIOCLEX) on Linux
All `ioctl(2)`s will fail on `O_PATH` file descriptors on Linux (because
they use `&empty_fops` as a security measure against `O_PATH` descriptors
affecting the backing file).
As a result, `File::try_clone()` and various other methods would always
fail with `-EBADF` on `O_PATH` file descriptors. The solution is to simply
use `F_SETFD` (as is used on other unices) which works on `O_PATH`
descriptors because it operates through the `fnctl(2)` layer and not
through `ioctl(2)`s.
Since this code is usually only used in strange error paths (a broken or
ancient kernel), the extra overhead of one syscall shouldn't cause any
dramas. Most other systems programming languages also use the fnctl(2)
so this brings us in line with them.
Fixes: rust-lang/rust#62314
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
core: check for pointer equality when comparing Eq slices
Because `Eq` types must be reflexively equal, an equal-length slice to the same memory location must be equal.
This is related to #33892 (and #32699) answering this comment from that PR:
> Great! One more easy question: why does this optimization not apply in the non-BytewiseEquality implementation directly above?
Because slices of non-reflexively equal types (like `f64`) are not equal even if it's the same slice. But if the types are `Eq`, we can use this same-address optimization, which this PR implements. Obviously this changes behavior if types violate the reflexivity condition of `Eq`, because their impls of `PartialEq` will no longer be called per-item, but 🤷♂ .
It's not clear how often this optimization comes up in the real world outside of the same-`&str` case covered by #33892, so **I'm requesting a perf run** (on MacOS today, so can't run `rustc_perf` myself). I'm going ahead and making the PR on the basis of being surprised things didn't already work this way.
This is my first time hacking rust itself, so as a perf sanity check I ran `./x.py bench --stage 0 src/lib{std,alloc}`, but the differences were noisy.
To make the existing specialization for `BytewiseEquality` explicit, it's now a supertrait of `Eq + Copy`. `Eq` should be sufficient, but `Copy` was included for clarity.
Rollup of 5 pull requests
Successful merges:
- #62275 (rustc_mir: treat DropAndReplace as Drop + Assign in qualify_consts.)
- #62465 (Sometimes generate storage statements for temporaries with type `!`)
- #62481 (Use `fold` in `Iterator::last` default implementation)
- #62493 (#62357: doc(ptr): add example for {read,write}_unaligned)
- #62532 (Some more cleanups to syntax::print)
Failed merges:
r? @ghost
Add a test for the issue resolved by removing `resolve_macro_path`
Add a test making sure that extern prelude entries introduced from an opaque macro are not visible anywhere, even it that macro
Fix test output after rebase
It's more convenient to have all this highly related stuff together on one screen (for future refactorings).
The `expand_invoc` function is compact enough now, after all the previous refactorings.
Remove a bunch of `Option`s that assumed that dummy fragment creation could fail.
The test output changed due to not performing the expansion in `fn expand_invoc` in case of the recursion limit hit.
The root expansion was missing one.
Expansions created for "derive containers" (see one of the next commits for the description) also didn't get expansion info.
Use variant names rather than descriptions for identifying desugarings in `#[rustc_on_unimplemented]`.
Both are highly unstable, but variant name is at least a single identifier.
