Fast path for stalled obligations on self ty
If we see that the `self` type of a goal is an infer var, then don't try to compute the goal at all, since we know that it'll be forced ambiguous.
This is currently only implemented when there are no opaques in the environment. We could extend it to check that the self type is not related to any already defined opaques via subtyping, but I'll leave that as a follow-up.
---
Also stall coerce and subtype predicates if both of their vars are not resolved to concrete types.
---
~~Also, we don't care if the goal is higher-ranked for the sized and copy/clone fast path.~~ pulling this out into another PR.
r? lcnr
Replace some `Option<Span>` with `Span` and use DUMMY_SP instead of None
Turns out many locations actually have a span available that we could use, so I used it
Add a new `mismatched-lifetime-syntaxes` lint
The lang-team [discussed this](https://hackmd.io/nf4ZUYd7Rp6rq-1svJZSaQ) and I attempted to [summarize](https://github.com/rust-lang/rust/pull/120808#issuecomment-2701863833) their decision. The summary-of-the-summary is:
- Using two different kinds of syntax for elided lifetimes is confusing. In rare cases, it may even [lead to unsound code](https://github.com/rust-lang/rust/issues/48686)! Some examples:
```rust
// Lint will warn about these
fn(v: ContainsLifetime) -> ContainsLifetime<'_>;
fn(&'static u8) -> &u8;
```
- Matching up references with no lifetime syntax, references with anonymous lifetime syntax, and paths with anonymous lifetime syntax is an exception to the simplest possible rule:
```rust
// Lint will not warn about these
fn(&u8) -> &'_ u8;
fn(&'_ u8) -> &u8;
fn(&u8) -> ContainsLifetime<'_>;
```
- Having a lint for consistent syntax of elided lifetimes will make the [future goal](https://github.com/rust-lang/rust/issues/91639) of warning-by-default for paths participating in elision much simpler.
---
This new lint attempts to accomplish the goal of enforcing consistent syntax. In the process, it supersedes and replaces the existing `elided-named-lifetimes` lint, which means it starts out life as warn-by-default.
The user has no clue what tail expression the compiler is talking
about: it is an implementation detail of the macro that it uses a block
with tail expression.
This adds an `iter!` macro that can be used to create movable
generators.
This also adds a yield_expr feature so the `yield` keyword can be used
within iter! macro bodies. This was needed because several unstable
features each need `yield` expressions, so this allows us to stabilize
them separately from any individual feature.
Co-authored-by: Oli Scherer <github35764891676564198441@oli-obk.de>
Co-authored-by: Jieyou Xu <jieyouxu@outlook.com>
Co-authored-by: Travis Cross <tc@traviscross.com>
Tweak fast path trait handling
(1.) Make it more sound by considering polarity (lol)
(2.) Make it more general, by considering higher-ranked size/copy/clone
(2.) Make it less observable, by only doing copy/clone fast path if there are no regions involved
r? lcnr
Specifically `TyAlias`, `Enum`, `Struct`, `Union`. So the fields match
the textual order in the source code.
The interesting part of the change is in
`compiler/rustc_hir/src/hir.rs`. The rest is extremely mechanical
refactoring.
add additional `TypeFlags` fast paths
Some crates, e.g. `diesel`, have items with a lot of where-clauses (more than 150). In these cases checking the `TypeFlags` of the whole `param_env` can be very beneficial.
This adds `fn fold_clauses` to mirror the existing `fn visit_clauses` and then uses this in folders which fold `ParamEnv`s.
Split out from rust-lang/rust#141451, depends on rust-lang/rust#141442.
r? `@compiler-errors`
Defer evaluating type system constants when they use infers or params
Split out of #137972, the parts necessary for associated const equality and min generic const args to make progress and have correct semantics around when CTFE is invoked. According to a [previous perf run](https://perf.rust-lang.org/compare.html?start=93257e2d20809d82d1bc0fcc1942480d1a66d7cd&end=01b4cbf0f47c3f782330db88fa5ba199bba1f8a2&stat=instructions:u) of adding the new `const_arg_kind` query we should expect minor regressions here.
I think this is acceptable as we should be able to remove this query relatively soon once mgca is more complete as we'll then be able to implement GCE in terms of mgca and rip out `GCEConst` at which point it's trivial to determine what kind of anon const we're dealing with (either it has generics and is a repeat expr hack, or it doesnt and is a normal anon const).
This should only affect unstable code as we handle repeat exprs specially and those are the only kinds of type system consts that are allowed to make use of generic parameters.
Fixes#133066Fixes#133199Fixes#136894Fixes#137813
r? compiler-errors
Rollup of 7 pull requests
Successful merges:
- #135562 (Add ignore value suggestion in closure body)
- #139635 (Finalize repeat expr inference behaviour with inferred repeat counts)
- #139668 (Handle regions equivalent to 'static in non_local_bounds)
- #140218 (HIR ty lowering: Clean up & refactor the lowering of type-relative paths)
- #140435 (use uX::from instead of _ as uX in non - const contexts)
- #141130 (rustc_on_unimplemented cleanups)
- #141286 (Querify `coroutine_hidden_types`)
Failed merges:
- #140247 (Don't build `ParamEnv` and do trait solving in `ItemCtxt`s when lowering IATs)
r? `@ghost`
`@rustbot` modify labels: rollup
Don't allow `poly_select` in new solver
I added a `poly_select` call in #140519, but this causes an ICE since the new solver doesn't properly handle the "instantiate binder -> recanonicalize" step in the proof tree visitor.
While we could fix the select visitor to look at the next step in proof tree, it's not really necessary. Instead, let's enforce that all callees call the non-higher-ranked `select` function in the new solver.
Fixes https://github.com/rust-lang/rust/issues/141322
r? lcnr
Normalize aliases to correct kind of error term
Fixes#140642
When normalizing an alias to an error in the old solver, normalize to the same term kind as the alias being normalized instead of always to a type error.
r? lcnr
Fix `FnOnce` impl for `AsyncFn`/`AsyncFnMut` self-borrowing closures in new solver
This only affects closures that are "`AsyncFn`/`AsyncFnMut`" in their calling capability that are being called with the `FnOnce` trait.
fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/217
r? lcnr
Querify `coroutine_hidden_types`
This is necessary if we ever want to add implied bounds that would be used for higher-ranked coroutine auto trait goals (e.g. future implements `Send`).
Modest perf regression in `hyper` full build which (afaict?) is the only async stress test, so definitely worth it IMO.
r? oli-obk
Fast path for processing some obligations in the new solver
Fast path applies to:
- Dyn compatibility predicates
- Region and type outlives predicates
- Trivially sized predicates
Document why we allow escaping bound vars in LTA norm
r? lcnr
followup from the const normalization PR. I think I now understand why free alias norm is funny about binders
Rollup of 7 pull requests
Successful merges:
- #141267 (only resolve top-level guard patterns' guards once)
- #141280 (Use Docker cache from the current repository)
- #141296 (Async drop fix for 'broken mir, place has deref as later projection')
- #141328 (When AsyncDrop impl is empty, sync drop generated in elaborator)
- #141332 (Do not eagerly fold consts in `normalize_param_env_or_error` if new solver)
- #141333 (Use `DeepRejectCtxt` in `assemble_inherent_candidates_from_param`)
- #141334 (eagerly check nested obligations when coercing fndefs)
r? `@ghost`
`@rustbot` modify labels: rollup
Do not eagerly fold consts in `normalize_param_env_or_error` if new solver
Fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/213
Given:
```
trait Trait: Deref<Target = [u8; { 1 + 1 }]> {}
```
when elaborating param env for `Trait`, we have `Self: Trait`, `Self: Deref<Target = [u8; {anon const}]>`.
Before this PR, we would fold the anon consts away *before* elaborating. However, we end up getting another *un-folded* copy of the anon const from elaborating `Self: Trait`. This leads to normalization ambiguity.
r? lcnr
Match on lang item kind instead of using an if/else chain
Similar to how the new solver does this. Just noticed while I was adding a new entry to the chain 😆
