Rollup of 9 pull requests
Successful merges:
- #104420 (Fix doc example for `wrapping_abs`)
- #104499 (rustdoc JSON: Use `Function` everywhere and remove `Method`)
- #104500 (`rustc_ast`: remove `ref` patterns)
- #104511 (Mark functions created for `raw-dylib` on x86 with DllImport storage class)
- #104595 (Add `PolyExistentialPredicate` type alias)
- #104605 (deduplicate constant evaluation in cranelift backend)
- #104628 (Revert "Update CI to use Android NDK r25b")
- #104662 (Streamline deriving on packed structs.)
- #104667 (Revert formatting changes of a test)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Add `PolyExistentialPredicate` type alias
Wrapping `ExistentialPredicate`s in a binder is very common, and this alias already exists for the `PolyExistential{TraitRef,Projection}` types.
Support using `Self` or projections inside an RPIT/async fn
I reuse the same idea as https://github.com/rust-lang/rust/pull/103449 to use variances to encode whether a lifetime parameter is captured by impl-trait.
The current implementation of async and RPIT replace all lifetimes from the parent generics by `'static`. This PR changes the scheme
```rust
impl<'a> Foo<'a> {
fn foo<'b, T>() -> impl Into<Self> + 'b { ... }
}
opaque Foo::<'_a>::foo::<'_b, T>::opaque<'b>: Into<Foo<'_a>> + 'b;
impl<'a> Foo<'a> {
// OLD
fn foo<'b, T>() -> Foo::<'static>::foo::<'static, T>::opaque::<'b> { ... }
^^^^^^^ the `Self` becomes `Foo<'static>`
// NEW
fn foo<'b, T>() -> Foo::<'a>::foo::<'b, T>::opaque::<'b> { ... }
^^ the `Self` stays `Foo<'a>`
}
```
There is the same issue with projections. In the example, substitute `Self` by `<T as Trait<'b>>::Assoc` in the sugared version, and `Foo<'_a>` by `<T as Trait<'_b>>::Assoc` in the desugared one.
This allows to support `Self` in impl-trait, since we do not replace lifetimes by `'static` any more. The same trick allows to use projections like `T::Assoc` where `Self` is allowed. The feature is gated behind a `impl_trait_projections` feature gate.
The implementation relies on 2 tweaking rules for opaques in 2 places:
- we only relate substs that correspond to captured lifetimes during TypeRelation;
- we only list captured lifetimes in choice region computation.
For simplicity, I encoded the "capturedness" of lifetimes as a variance, `Bivariant` vs `Invariant` for unused vs captured lifetimes. The `variances_of` query used to ICE for opaques.
Impl-trait that do not reference `Self` or projections will have their variances as:
- `o` (invariant) for each parent type or const;
- `*` (bivariant) for each parent lifetime --> will not participate in borrowck;
- `o` (invariant) for each own lifetime.
Impl-trait that does reference `Self` and/or projections will have some parent lifetimes marked as `o` (as the example above), and participate in type relation and borrowck. In the example above, `variances_of(opaque) = ['_a: o, '_b: *, T: o, 'b: o]`.
r? types
cc `@compiler-errors` , as you asked about the issue with `Self` and projections.
privacy: Rename "accessibility levels" to "effective visibilities"
And a couple of other naming and comment tweaks.
Related to https://github.com/rust-lang/rust/issues/48054
For `enum Level` I initially used naming `enum EffectiveVisibilityLevel`, but it was too long and inconvenient because it's used pretty often.
So I shortened it to just `Level`, if it needs to be used from some context where this name would be ambiguous, then it can be imported with renaming like `use rustc_middle::privacy::Level as EffVisLevel` or something.
Fix line numbers for MIR inlined code
`should_collapse_debuginfo` detects if the specified span is part of a
macro expansion however it does this by checking if the span is anything
other than a normal (non-expanded) kind, then the span sequence is
walked backwards to the root span.
This doesn't work when the MIR inliner inlines code as it creates spans
with expansion information set to `ExprKind::Inlined` and results in the
line number being attributed to the inline callsite rather than the
normal line number of the inlined code.
Fixes#103068
stop using `ty::UnevaluatedConst` directly
best reviewed commit by commit.
simplifies #99798 because we now don't have to expand `ty::UnevaluatedConst` to `ty::Const`.
I also remember some other places where using `ty::UnevaluatedConst` directly was annoying and caused issues, though I don't quite remember what they were rn '^^
r? `@oli-obk` cc `@JulianKnodt`
indirect immutable freeze by-value function parameters.
Right now, `rustc` only examines function signatures and the platform ABI when
determining the LLVM attributes to apply to parameters. This results in missed
optimizations, because there are some attributes that can be determined via
analysis of the MIR making up the function body. In particular, `readonly`
could be applied to most indirectly-passed by-value function arguments
(specifically, those that are freeze and are observed not to be mutated), but
it currently is not.
This patch introduces the machinery that allows `rustc` to determine those
attributes. It consists of a query, `deduced_param_attrs`, that, when
evaluated, analyzes the MIR of the function to determine supplementary
attributes. The results of this query for each function are written into the
crate metadata so that the deduced parameter attributes can be applied to
cross-crate functions. In this patch, we simply check the parameter for
mutations to determine whether the `readonly` attribute should be applied to
parameters that are indirect immutable freeze by-value. More attributes could
conceivably be deduced in the future: `nocapture` and `noalias` come to mind.
Adding `readonly` to indirect function parameters where applicable enables some
potential optimizations in LLVM that are discussed in [issue 103103] and [PR
103070] around avoiding stack-to-stack memory copies that appear in functions
like `core::fmt::Write::write_fmt` and `core::panicking::assert_failed`. These
functions pass a large structure unchanged by value to a subfunction that also
doesn't mutate it. Since the structure in this case is passed as an indirect
parameter, it's a pointer from LLVM's perspective. As a result, the
intermediate copy of the structure that our codegen emits could be optimized
away by LLVM's MemCpyOptimizer if it knew that the pointer is `readonly
nocapture noalias` in both the caller and callee. We already pass `nocapture
noalias`, but we're missing `readonly`, as we can't determine whether a
by-value parameter is mutated by examining the signature in Rust. I didn't have
much success with having LLVM infer the `readonly` attribute, even with fat
LTO; it seems that deducing it at the MIR level is necessary.
No large benefits should be expected from this optimization *now*; LLVM needs
some changes (discussed in [PR 103070]) to more aggressively use the `noalias
nocapture readonly` combination in its alias analysis. I have some LLVM patches
for these optimizations and have had them looked over. With all the patches
applied locally, I enabled LLVM to remove all the `memcpy`s from the following
code:
```rust
fn main() {
println!("Hello {}", 3);
}
```
which is a significant codegen improvement over the status quo. I expect that
if this optimization kicks in in multiple places even for such a simple
program, then it will apply to Rust code all over the place.
[issue 103103]: https://github.com/rust-lang/rust/issues/103103
[PR 103070]: https://github.com/rust-lang/rust/pull/103070
`should_collapse_debuginfo` detects if the specified span is part of a
macro expansion however it does this by checking if the span is anything
other than a normal (non-expanded) kind, then the span sequence is
walked backwards to the root span.
This doesn't work when the MIR inliner inlines code as it creates spans
with expansion information set to `ExprKind::Inlined` and results in the
line number being attributed to the inline callsite rather than the
normal line number of the inlined code.
Initial implementation of dyn*
This PR adds extremely basic and incomplete support for [dyn*](https://smallcultfollowing.com/babysteps//blog/2022/03/29/dyn-can-we-make-dyn-sized/). The goal is to get something in tree behind a flag to make collaboration easier, and also to make sure the implementation so far is not unreasonable. This PR does quite a few things:
* Introduce `dyn_star` feature flag
* Adds parsing for `dyn* Trait` types
* Defines `dyn* Trait` as a sized type
* Adds support for explicit casts, like `42usize as dyn* Debug`
* Including const evaluation of such casts
* Adds codegen for drop glue so things are cleaned up properly when a `dyn* Trait` object goes out of scope
* Adds codegen for method calls, at least for methods that take `&self`
Quite a bit is still missing, but this gives us a starting point. Note that this is never intended to become stable surface syntax for Rust, but rather `dyn*` is planned to be used as an implementation detail for async functions in dyn traits.
Joint work with `@nikomatsakis` and `@compiler-errors.`
r? `@bjorn3`
ssa: implement `#[collapse_debuginfo]`
cc #39153rust-lang/compiler-team#386
Debuginfo line information for macro invocations are collapsed by default - line information are replaced by the line of the outermost expansion site. Using `-Zdebug-macros` disables this behaviour.
When the `collapse_debuginfo` feature is enabled, the default behaviour is reversed so that debuginfo is not collapsed by default. In addition, the `#[collapse_debuginfo]` attribute is available and can be applied to macro definitions which will then have their line information collapsed.
r? rust-lang/wg-debugging
