Improve SIMD type element count validation
Resolvesrust-lang/stdsimd#53.
These changes are motivated by `stdsimd` moving in the direction of const generic vectors, e.g.:
```rust
#[repr(simd)]
struct SimdF32<const N: usize>([f32; N]);
```
This makes a few changes:
* Establishes a maximum SIMD lane count of 2^16 (65536). This value is arbitrary, but attempts to validate lane count before hitting potential errors in the backend. It's not clear what LLVM's maximum lane count is, but cranelift's appears to be much less than `usize::MAX`, at least.
* Expands some SIMD intrinsics to support arbitrary lane counts. This resolves the ICE in the linked issue.
* Attempts to catch invalid-sized vectors during typeck when possible.
Unresolved questions:
* Generic-length vectors can't be validated in typeck and are only validated after monomorphization while computing layout. This "works", but the errors simply bail out with no context beyond the name of the type. Should these errors instead return `LayoutError` or otherwise provide context in some way? As it stands, users of `stdsimd` could trivially produce monomorphization errors by making zero-length vectors.
cc `@bjorn3`
expand/resolve: Turn `#[derive]` into a regular macro attribute
This PR turns `#[derive]` into a regular attribute macro declared in libcore and defined in `rustc_builtin_macros`, like it was previously done with other "active" attributes in https://github.com/rust-lang/rust/pull/62086, https://github.com/rust-lang/rust/pull/62735 and other PRs.
This PR is also a continuation of #65252, #69870 and other PRs linked from them, which layed the ground for converting `#[derive]` specifically.
`#[derive]` still asks `rustc_resolve` to resolve paths inside `derive(...)`, and `rustc_expand` gets those resolution results through some backdoor (which I'll try to address later), but otherwise `#[derive]` is treated as any other macro attributes, which simplifies the resolution-expansion infra pretty significantly.
The change has several observable effects on language and library.
Some of the language changes are **feature-gated** by [`feature(macro_attributes_in_derive_output)`](https://github.com/rust-lang/rust/issues/81119).
#### Library
- `derive` is now available through standard library as `{core,std}::prelude::v1::derive`.
#### Language
- `derive` now goes through name resolution, so it can now be renamed - `use derive as my_derive; #[my_derive(Debug)] struct S;`.
- `derive` now goes through name resolution, so this resolution can fail in corner cases. Crater found one such regression, where import `use foo as derive` goes into a cycle with `#[derive(Something)]`.
- **[feature-gated]** `#[derive]` is now expanded as any other attributes in left-to-right order. This allows to remove the restriction on other macro attributes following `#[derive]` (https://github.com/rust-lang/reference/issues/566). The following macro attributes become a part of the derive's input (this is not a change, non-macro attributes following `#[derive]` were treated in the same way previously).
- `#[derive]` is now expanded as any other attributes in left-to-right order. This means two derive attributes `#[derive(Foo)] #[derive(Bar)]` are now expanded separately rather than together. It doesn't generally make difference, except for esoteric cases. For example `#[derive(Foo)]` can now produce an import bringing `Bar` into scope, but previously both `Foo` and `Bar` were required to be resolved before expanding any of them.
- **[feature-gated]** `#[derive()]` (with empty list in parentheses) actually becomes useful. For historical reasons `#[derive]` *fully configures* its input, eagerly evaluating `cfg` everywhere in its target, for example on fields.
Expansion infra doesn't do that for other attributes, but now when macro attributes attributes are allowed to be written after `#[derive]`, it means that derive can *fully configure* items for them.
```rust
#[derive()]
#[my_attr]
struct S {
#[cfg(FALSE)] // this field in removed by `#[derive()]` and not observed by `#[my_attr]`
field: u8
}
```
- `#[derive]` on some non-item targets is now prohibited. This was accidentally allowed as noop in the past, but was warned about since early 2018 (#50092), despite that crater found a few such cases in unmaintained crates.
- Derive helper attributes used before their introduction are now reported with a deprecation lint. This change is long overdue (since macro modularization, https://github.com/rust-lang/rust/issues/52226#issuecomment-422605033), but it was hard to do without fixing expansion order for derives. The deprecation is tracked by #79202.
```rust
#[trait_helper] // warning: derive helper attribute is used before it is introduced
#[derive(Trait)]
struct S {}
```
Crater analysis: https://github.com/rust-lang/rust/pull/79078#issuecomment-731436821
Identify unreachable subpatterns more reliably
In https://github.com/rust-lang/rust/pull/80104 I used `Span`s to identify unreachable sub-patterns in the presence of or-patterns during exhaustiveness checking. In https://github.com/rust-lang/rust/issues/80501 it was revealed that `Span`s are complicated and that this was not a good idea.
Instead, this PR identifies subpatterns logically: as a path in the tree of subpatterns of a given pattern. I made a struct that captures a set of such subpatterns. This is a bit complex, but thankfully self-contained; the rest of the code does not need to know anything about it.
Fixes https://github.com/rust-lang/rust/issues/80501. I think I managed to keep the perf neutral.
r? `@varkor`
Rollup of 5 pull requests
Successful merges:
- #81526 (btree: use Option's unwrap_unchecked())
- #81742 (Add a note about the correctness and the effect on unsafe code to the `ExactSizeIterator` docs)
- #81830 (Add long error explanation for E0542)
- #81835 (Improve long explanation for E0546)
- #81843 (Add regression test for #29821)
Failed merges:
- #81836 (Add long explanation for E0547)
r? `@ghost`
`@rustbot` modify labels: rollup
Add abi field to `Method`
Also bumps version and adds a test (Will conflict with #81500, whichever is merged first)
Rationale: It's possible for methods to have an ABI. This should be exposed in the JSON.
Add test for #75158
This also shifts some type-size related tests into a new directory, so that we keep the number of files at the root down.
Closes#75158
Upgrade wasm32 image to Ubuntu 20.04
This switches the wasm32 image, which is used to test
wasm32-unknown-emscripten, to Ubuntu 20.04. While at it, enable
most of the excluded tests, as they seem to work fine with some
minor fixes.
Remove some function fields
Same kind as #80845.
This PR removes the `all_types` and `ret_types` from the `clean::Function` type.
Another change that I had to do was implementing the `From` trait to be able to convert `hir::def::DefKind` into `clean::TypeKind` without requiring `DocContext` (and so I updated the `clean` method so that it's taken into account).
The last two commits improve a bit the `get_real_types` function and the `Type::generics` method.
r? `@jyn514`
Add a test for escaping LLVMisms in inline asm
We escape certain LLVM-specific features when passing the inline
assembly string to the LLVM. Until now, however, there was no test
making sure this behaviour stays intact. This commit adds such a test!
r? `@Amanieu`
cc `@joshtriplett`
typeck: Emit structured suggestions for tuple struct syntax
And tuple variant syntax, but that didn't fit in the subject :)
Now the fact that these are suggestions is exposed both to the layout
engine and to IDEs and rustfix for automatic application.
Refactor `PrimitiveTypeTable` for Clippy
I removed `PrimitiveTypeTable` and added `PrimTy::ALL` and `PrimTy::from_name` in its place. This allows Clippy to use `PrimTy::from_name` for the `builtin_type_shadow` lint, and a `const` list of primitive types is deleted from Clippy code (the goal). All changes should be a little faster, if anything.
tidy: Run tidy style against markdown files.
This adds tidy checks for markdown files. I think it is useful to have some style enforcement (for the same reasons the style is enforced on other files). I think it is worthwhile to avoid `ignore` on rust examples since having broken code in documentation is frustrating. Avoiding trailing whitespace is good because it has semantic meaning in markdown, which I think should be avoided.
We escape certain LLVM-specific features when passing the inline
assembly string to the LLVM. Until now, however, there was no test
making sure this behaviour stays intact. This commit adds such a test!
This switches the wasm32 image, which is used to test
wasm32-unknown-emscripten to Ubuntu 20.04. While at it, enable
most of the excluded tests, as they seem to work fine with some
minor fixes.
Make rustdoc respect `--error-format short` in doctests
Note that this will not work with `cargo test`, only with `rustdoc --test`, I'll have to modify `cargo` as well.
Fix#81662.
`@rustbot` label +T-rustdoc +A-doctests
Revert 78373 ("dont leak return value after panic in drop")
Short term resolution for issue #80949.
Reopen#47949 after this lands.
(We plan to fine-tune PR #78373 to not run into this problem.)
