`best_blame_constraint`: Blame better constraints when the region graph has cycles from invariance or `'static`
This fixes#132749 by changing which constraint is blamed for region errors in several cases. `best_blame_constraint` had a heuristic that tried to pinpoint the constraint causing an error by filtering out any constraints where the outliving region is unified with the ultimate target region being outlived. However, it used the SCCs of the region graph to do this, which is unreliable; in particular, if the target region is `'static`, or if there are cycles from the presence of invariant types, it was skipping over the constraints it should be blaming. As is the case in that issue, this could lead to confusing diagnostics. The simplest fix seems to work decently, judging by test stderr: this makes `best_blame_constraint` no longer filter constraints by their outliving region's SCC.
There are admittedly some quirks in the test output. In many cases, subdiagnostics that depend on the particular constraint being blamed have either started or stopped being emitted. After starting at this for quite a while, I think anything too fickle about whether it outputs based on the particular constraint being blamed should instead be looking at the constraint path as a whole, similar to what's done for [the placeholder-from-predicate note](https://github.com/rust-lang/rust/compare/master...dianne:rust:better-blame-constraints-for-static#diff-3c0de6462469af483c9ecdf2c4b00cb26192218ef2d5c62a0fde75107a74caaeR506).
Very many tests involving invariant types gained a note pointing out the types' invariance, but in a few cases it was lost. A particularly illustrative example is [tests/ui/lifetimes/copy_modulo_regions.stderr](https://github.com/rust-lang/rust/compare/master...dianne:rust:better-blame-constraints-for-static?expand=1#diff-96e1f8b29789b3c4ce2f77a5e0fba248829b97ef9d1ce39e7d2b4aa57b2cf4f0); I'd argue the new constraint is a better one to blame, but it lacks the variance diagnostic information that's elsewhere in the constraint path. If desired, I can try making that note check the whole path rather than just the blamed constraint.
The subdiagnostic [`BorrowExplanation::add_object_lifetime_default_note`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_borrowck/diagnostics/explain_borrow/enum.BorrowExplanation.html#method.add_object_lifetime_default_note) depends on a `Cast` being blamed, so [a special case](364ca7f99c) was necessary to keep it from disappearing from tests specifically testing for it. However, see the FIXME comment in that commit; I think the special case should be removed once that subdiagnostic works properly, but it's nontrivial enough to warrant a separate PR. Incidentally, this removes the note from a test where it was being added erroneously: in [tests/ui/borrowck/two-phase-surprise-no-conflict.stderr](https://github.com/rust-lang/rust/compare/master...dianne:rust:better-blame-constraints-for-static?expand=1#diff-8cf085af8203677de6575a45458c9e6b03412a927df879412adec7e4f7ff5e14), the object lifetime is explicitly provided and it's not `'static`.
Don't enable anyhow's `backtrace` feature in opt-dist
As of the stabilization of `std::backtrace` in Rust 1.65, this package flag has no effect other than to enable an unused dependency on the `backtrace` crate.
(See <af0937ef72/Cargo.toml (L18-L23)>.)
While the presence of this feature in opt-dist doesn't cause other tools (which use anyhow) to actually *build* backtrace, it does affect the global crate graph used for dependency version resolution. After removing this feature, we can use `cargo tree --invert --package backtrace` to see that the only remaining reverse-dependency of backtrace is `color-eyre`, which is used by `ui_test`.
As of the stabilization of `std::backtrace` in Rust 1.65, this package flag has
no effect other than to enable an unused dependency on the `backtrace` crate.
cg_llvm: Use constants for DWARF opcodes, instead of FFI calls
Split off from #134009 to incorporate feedback from https://github.com/rust-lang/rust/pull/134009#discussion_r1903133906.
Most of the constant values now come from gimli, which is already a compiler dependency.
I noticed that `DW_OP_LLVM_fragment` is an LLVM detail that is not defined by DWARF and could hypothetically change, so I added a static assertion on the C++ side to detect that if it ever happens.
r? workingjubilee
bootstrap: Don't apply -Ztls-model=initial-exec to deps of proc-macros
Fixes#134863
1. Checks if a crate name is in a static list before applying the flag
2. Adds a tidy check that gathers transitive deps of proc macros and ensures the list is up to date
cc `@bjorn3` - the issue specifies `rustc_fluent_macro` but I assume this applies to all proc macro crates.
Fix logical error with what text is considered whitespace.
There appears to be a logical issue around what counts as leading white-space. There is code which does a subtraction assuming that no errors will be reported inside the leading whitespace. However we compute the length of that whitespace with std::char::is_whitespace and not rustc_lexer::is_whitespace. The former will include a no-break space while later will excluded it. We can only safely make the assumption that no errors will be reported in whitespace if it is all "Rust Standard" whitespace. Indeed an error does occur in unicode whitespace if it contains a no-break space. In that case the subtraction will cause a ICE (for a compiler in debug mode) as described in https://github.com/rust-lang/rust/issues/132918.
Split up attribute parsing code and move data types to `rustc_attr_data_structures`
This change renames `rustc_attr` to `rustc_attr_parsing`, and splits up the parsing code. At the same time, all the data types used move to `rustc_attr_data_structures`. This is in preparation of also having a third crate: `rustc_attr_validation`
I initially envisioned this as two separate PRs, but I think doing it in one go reduces the number of ways others would have to rebase their changes on this. However, I can still split them.
r? `@oli-obk` (we already discussed how this is a first step in a larger plan)
For a more detailed plan on how attributes are going to change, see https://github.com/rust-lang/rust/issues/131229
Edit: this looks like a giant PR, but the changes are actually rather trivial. Each commit is reviewable on its own, and mostly moves code around. No new logic is added.
There is a logical issue around what counts as leading white-space.
There is code which does a subtraction assuming that no errors will be reported
inside the leading whitespace. However we compute the length of
that whitespace with std::char::is_whitespace and not
rustc_lexer::is_whitespace. The former will include a no-break space while
later will excluded it. We can only safely make the assumption that no errors
will be reported in whitespace if it is all "Rust Standard" whitespace.
Indeed an error does occur in unicode whitespace if it contains a no-break
space.
`CheckAttrVisitor::check_doc_keyword` checks `#[doc(keyword = "..")]`
attributes to ensure they are on an empty module, and that the value is
a non-empty identifier.
The `rustc::existing_doc_keyword` lint checks these attributes to ensure
that the value is the name of a keyword.
It's silly to have two different checking mechanisms for these
attributes. This commit does the following.
- Changes `check_doc_keyword` to check that the value is the name of a
keyword (avoiding the need for the identifier check, which removes a
dependency on `rustc_lexer`).
- Removes the lint.
- Updates tests accordingly.
There is one hack: the `SelfTy` FIXME case used to used to be handled by
disabling the lint, but now is handled with a special case in
`is_doc_keyword`. That hack will go away if/when the FIXME is fixed.
Co-Authored-By: Guillaume Gomez <guillaume1.gomez@gmail.com>
Lint on combining `#[no_mangle]` and `#[export_name]`
This is my very first contribution to the compiler, even though I read the [chapter about lints](https://rustc-dev-guide.rust-lang.org/diagnostics.html) I'm not very certain that this ~~new lint is done right as a builtin lint~~ PR is right. I appreciate any guidance on how to improve the code.
- Add test for issue #47446
- ~~Implement the new lint `mixed_export_name_and_no_mangle` as a builtin lint (not sure if that is the right way to go)~~ Extend `unused_attributes` lint
- Add suggestion how to fix it
<details>
<summary>Old proposed new lint</summary>
> The `mixed_export_name_and_no_mangle` lint detects usage of both `#[export_name]` and `#[no_mangle]` on the same item which results on `#[no_mangle]` being ignored.
>
> *warn-by-default*
>
> ### Example
>
> ```rust
> #[no_mangle] // ignored
> #[export_name = "foo"] // takes precedences
> pub fn bar() {}
> ```
>
> ### Explanation
>
> The compiler will not respect the `#[no_mangle]` attribute when generating the symbol name for the function, as the `#[export_name]` attribute takes precedence. This can lead to confusion and is unnecessary.
</details>
Remove `HybridBitSet`
`HybridBitSet` was introduced under the name `HybridIdxSetBuf` way back in #53383 where it was a big win for NLL borrow checker performance. In #93984 the more flexible `ChunkedBitSet` was added. Uses of `HybridBitSet` have gradually disappeared (e.g. #116152) and there are now few enough that they can be replaced with `BitSet` or `ChunkedBitSet`, and `HybridBitSet` can be removed, cutting more than 700 lines of code.
r? `@Mark-Simulacrum`
This reduces code sizes and better respects programmer intent when
marking inline(never). Previously such a marking was essentially ignored
for generic functions, as we'd still inline them in remote crates.
[AIX] change system dynamic library format
Historically on AIX, almost all dynamic libraries are distributed in `.a` Big Archive Format which can consists of both static and shared objects in the same archive (e.g. `libc++abi.a(libc++abi.so.1)`). During the initial porting process, the dynamic libraries are kept as `.a` to simplify the migration, but semantically having an XCOFF object under the archive extension is wrong. For crate type `cdylib` we want to be able to distribute the libraries as archives as well.
We are migrating to archives with the following format:
```
$ ar -t lib<name>.a
lib<name>.so
```
where each archive contains a single member that is a shared XCOFF object that can be loaded.
