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Fix some unnecessary casts
`x clippy compiler -Aclippy::all -Wclippy::unnecessary_cast --fix` with some manual review to ensure every fix is correct.
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Similar to the previous commit, this replaces `newtype_index`'s opt-out
`no_ord_impl` attribute with the opt-in `orderable` attribute.
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`x clippy compiler -Aclippy::all -Wclippy::unnecessary_cast --fix`
with some manual review to ensure every fix is correct.
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`x clippy compiler -Aclippy::all -Wclippy::needless_borrow --fix`.
Then I had to remove a few unnecessary parens and muts that were exposed
now.
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Use `copied` instead of manual `map`
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- `ReFree` -> `ReLateParam`
- `ReEarlyBound` -> `ReEarlyParam`
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Remove `-Zperf-stats`.
The included measurements have varied over the years. At one point there were quite a few more, but #49558 deleted a lot that were no longer used. Today there's just four, and it's a motley collection that doesn't seem particularly valuable.
I think it has been well and truly subsumed by self-profiling, which collects way more data.
r? `@wesleywiser`
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- `RegionVariableOrigin::~~Late~~BoundRegion`
- `~~Late~~BoundRegionConversionTime`
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other changes:
- `Region::new_late_bound` -> `Region::new_bound`
- `Region::is_late_bound` -> `Region::is_bound`
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The included measurements have varied over the years. At one point there
were quite a few more, but #49558 deleted a lot that were no longer
used. Today there's just four, and it's a motley collection that doesn't
seem particularly valuable.
I think it has been well and truly subsumed by self-profiling, which
collects way more data.
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`rustc_span` cleanups
Just some things I found while looking over this crate.
r? `@oli-obk`
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Most notably, this commit changes the `pub use crate::*;` in that file
to `use crate::*;`. This requires a lot of `use` items in other crates
to be adjusted, because everything defined within `rustc_span::*` was
also available via `rustc_span::source_map::*`, which is bizarre.
The commit also removes `SourceMap::span_to_relative_line_string`, which
is unused.
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r=aliemjay
Consider alias bounds when computing liveness in NLL (but this time sound hopefully)
This is a revival of #116040, except removing the changes to opaque lifetime captures check to make sure that we're not triggering any unsoundness due to the lack of general existential regions and the currently-existing `ReErased` hack we use instead.
r? `@aliemjay` -- I appreciate you pointing out the unsoundenss in the previous iteration of this PR, and I'd like to hear that you're happy with this iteration of this PR before this goes back into FCP :>
Fixes #116794 as well
---
(mostly copied from #116040 and reworked slightly)
# Background
Right now, liveness analysis in NLL is a bit simplistic. It simply walks through all of the regions of a type and marks them as being live at points. This is problematic in the case of aliases, since it requires that we mark **all** of the regions in their args[^1] as live, leading to bugs like #42940.
In reality, we may be able to deduce that fewer regions are allowed to be present in the projected type (or "hidden type" for opaques) via item bounds or where clauses, and therefore ideally, we should be able to soundly require fewer regions to be live in the alias.
For example:
```rust
trait Captures<'a> {}
impl<T> Captures<'_> for T {}
fn capture<'o>(_: &'o mut ()) -> impl Sized + Captures<'o> + 'static {}
fn test_two_mut(mut x: ()) {
let _f1 = capture(&mut x);
let _f2 = capture(&mut x);
//~^ ERROR cannot borrow `x` as mutable more than once at a time
}
```
In the example above, we should be able to deduce from the `'static` bound on `capture`'s opaque that even though `'o` is a captured region, it *can never* show up in the opaque's hidden type, and can soundly be ignored for liveness purposes.
# The Fix
We apply a simple version of RFC 1214's `OutlivesProjectionEnv` and `OutlivesProjectionTraitDef` rules to NLL's `make_all_regions_live` computation.
Specifically, when we encounter an alias type, we:
1. Look for a unique outlives bound in the param-env or item bounds for that alias. If there is more than one unique region, bail, unless any of the outlives bound's regions is `'static`, and in that case, prefer `'static`. If we find such a unique region, we can mark that outlives region as live and skip walking through the args of the opaque.
2. Otherwise, walk through the alias's args recursively, as we do today.
## Limitation: Multiple choices
This approach has some limitations. Firstly, since liveness doesn't use the same type-test logic as outlives bounds do, we can't really try several options when we're faced with a choice.
If we encounter two unique outlives regions in the param-env or bounds, we simply fall back to walking the opaque via its args. I expect this to be mostly mitigated by the special treatment of `'static`, and can be fixed in a forwards-compatible by a more sophisticated analysis in the future.
## Limitation: Opaque hidden types
Secondly, we do not employ any of these rules when considering whether the regions captured by a hidden type are valid. That causes this code (cc #42940) to fail:
```rust
trait Captures<'a> {}
impl<T> Captures<'_> for T {}
fn a() -> impl Sized + 'static {
b(&vec![])
}
fn b<'o>(_: &'o Vec<i32>) -> impl Sized + Captures<'o> + 'static {}
```
We need to have existential regions to avoid [unsoundness](https://github.com/rust-lang/rust/pull/116040#issuecomment-1751628189) when an opaque captures a region which is not represented in its own substs but which outlives a region that does.
## Read more
Context: https://github.com/rust-lang/rust/pull/115822#issuecomment-1731153952 (for the liveness case)
More context: https://github.com/rust-lang/rust/issues/42940#issuecomment-455198309 (for the opaque capture case, which this does not fix)
[^1]: except for bivariant region args in opaques, which will become less relevant when we move onto edition 2024 capture semantics for opaques.
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Fix #89868.
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When encountering an associated item with a type param that could be
constrained, do not look at the parent item if the type param comes from
the associated item.
Fix #117209.
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Instead we use `Display` impls and their `alternate` render scheme to
decide whether we want backticks or not.
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`OptWithInfcx` naming nits, trait bound simplifications
* Use an associated type `Interner` on `InferCtxtLike` to remove a redundant interner parameter (`I: Interner, Infcx: InferCtxtLike<I>` -> `Infcx: InferCtxtLike`).
* Remove double-`Option` between `infcx: Option<Infcx>` and `fn universe_of_ty(&self, ty: ty::InferTy) -> Option<ty::UniverseIndex>`. We don't need the infcx to be optional if we can provide a "noop" (`NoInfcx`) implementation that just always returns `None` for universe index.
* Also removes the `core::convert::Infallible` implementation which I found a bit weird...
* Some naming nits with params.
* I found `InferCtxt` + `InfCtx` and `Infcx` to be a lot of different ways to spell "inference context", so I got rid of the `InfCtx` type parameter name in favor of `Infcx` which is a more standard name.
* I found `OptWithInfcx` to be a bit redundant -> `WithInfcx`.
I'm making these changes because I intend to reuse the `InferCtxtLike` trait for uplifting the canonicalizer into a new trait -- conveniently, the information I need for uplifting the canonicalizer also is just the universe information of a type var, so it's super convenient 😸
r? `@BoxyUwU` or `@lcnr`
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Make `ty::print::Printer` take `&mut self` instead of `self`
based on #116815
This simplifies the code by removing all the `self` assignments and
makes the flow of data clearer - always into the printer.
Especially in v0 mangling, which already used `&mut self` in some
places, it gets a lot more uniform.
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Suggest `;` after bare `match` expression E0308
Fix #72634.
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This simplifies the code by removing all the `self` assignments and
makes the flow of data clearer - always into the printer.
Especially in v0 mangling, which already used `&mut self` in some
places, it gets a lot more uniform.
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Tweak wording of type errors involving type params
Fix #78206.
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Fix #78206.
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Rollup of 5 pull requests
Successful merges:
- #116812 (Disable missing_copy_implementations lint on non_exhaustive types)
- #116856 (Disable effects in libcore again)
- #116865 (Suggest constraining assoc types in more cases)
- #116870 (Don't compare host param by name)
- #116879 (revert #114586)
r? `@ghost`
`@rustbot` modify labels: rollup
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revert #114586
Reverts #114586.
cc #116877 (not closing until this gets a beta backport)
fixes #116684
fixes https://github.com/rust-lang/rust/pull/114586#issuecomment-1751967321
r? `@oli-obk` or `@lcnr`
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Fix #46969.
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All printing goes through `fmt::Error` now.
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It's always a `fmt::Error` except in some cases where it was `!`, but
we're not really winning anything in that case.
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Now that `Printer` doesn't have subprinters anymore, the output of a
printing operation is always the same.
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These are `Self` in almost all printers except one, which can just store
the state as a field instead. This simplifies the printer and allows for
further simplifications, for example using `&mut self` instead of
passing around the printer.
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Fix #72634.
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Relate alias ty with variance
In the new solver, turns out that the subst-relate branch of the alias-relate predicate was relating args invariantly even for opaques, which have variance :skull:.
This change is a bit more invasive, but I'd rather not special-case it [here](https://github.com/rust-lang/rust/blob/aeaa5c30e5c9041264a2e8314b68ad84c2dc3169/compiler/rustc_trait_selection/src/solve/alias_relate.rs#L171-L190) and then have it break elsewhere. I'm doing a perf run to see if the extra call to `def_kind` is that expensive, if it is, I'll reconsider.
r? ``@lcnr``
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