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
HIR ty lowering: Clean up & refactor the lowering of type-relative paths
While rebasing #126651 I realized that HIR ty lowering could benefit from some *spring cleaning* now that it's been extended to handle RTN and mGCA paths.
More seriously, similar to my merged PR #118668 which unified the handling of all *associated item constraints* (assoc ty, const (ACE) & fn (RTN)), this PR (commit 695fcf517d) partially[^1] deduplicates the resolution code for all *type-relative paths* (assoc ty, const (mGCA) & fn (RTN)).
**Why**? DRY'ing that part of the code means PR #126651 will automatically support RTN paths like `Ty::AssocTy::assoc_fn(..)` and it also implies shared diagnostic code and thus better diagnostics for RTN.
---
The other commits represent cleanups, renamings, moves. More notably, I've renamed path lowering methods to be a lot more descriptive, so ones lowering `QPath(Resolved)` paths now have `_resolved_` in their name and ones lowering `QPath(TypeRelative)` paths now have `_type_relative_` in their name. This should make it stupidly obvious what their purpose is.
---
Best reviewed commit by commit. The changes are close to trivial but the diff might make it look hairier.
r? compiler-errors
[^1]: Sadly, I couldn't unify as much compared to the other PR without introducing unnecessary `unreachable!()`s or rendering the code otherwise illegible with flags and micro helper traits.
Handle regions equivalent to 'static in non_local_bounds
`non_local_bounds` would only find non local bounds that strictly bound a given region, but it's possible that a local region is equated to 'static when showing a type referencing a locally bound lifetime, such as `dyn Any + 'a` in the tests added, is well-formed. In this case we should return 'static.
closes#122704closes#139004
Finalize repeat expr inference behaviour with inferred repeat counts
I believe this should be the last change of how repeat exprs are handled before it's finished for `generic_arg_infer`. Assuming we don't wind up deciding to replace this all with a new predicate kind :)
This PR has three actual changes:
- Always defer the checks to end of typeck even when generic arg infer is not enabled (needs an FCP)
- Properly handle element exprs that are constants when the repeat count is inferred
- "Isolate" each repeat expr check so that inference constraints from `Copy` goals dont affect other repeat expr checks resulting in weird order-dependent inference
The commit history and tests should be relatively helpful for understanding this PR's impl.
r? compiler-errors
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
dont handle bool transmute
removes `transmute(u8) -> bool` suggestion due to ambiguity, leave it for clippy
elaboration on ambiguity in question:
`transmute::<u8, bool>(x)` will codegen to an `assume(u8 < 2)`;
`_ == 1` or `_ != 0` or `_ % 2 == 0` would remove that assumption
`match _ { x @ (0 | 1) => x == 1, _ => std::hint::unreachable_unchecked() }` is very verbose
`@rustbot` label L-unnecessary_transmutes
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
`unpretty=thir-tree`: don't require the final expr to be the body's value
Two motivations for this:
- I couldn't find a comment motivating this hard-coding. I can imagine it might be easier to read `unpretty=thir-flat` output if the final expression in the THIR is always the body's value, but if that's the reason, that should be the justification in the source. I can also imagine it's meant to check that all expressions will be visited by the pretty-printer, but the existing check doesn't quite do that either.
- Guard patterns (#129967) contain expressions, so lowering params containing guard patterns may add more expressions to the THIR. Currently a body's params are lowered after its expression, so guard expressions in params would end up last, breaking this. As an alternative, the params could be lowered first (#141356).
lower bodies' params to thir before the body's value
Two motivations for this:
- Lowering params first means errors from lowering the params are emitted before errors from lowering the body's expression. This comes up in [tests/ui/associated-consts/associated-const-type-parameter-pattern.stderr](https://github.com/rust-lang/rust/compare/master...dianne:rust:thir-lower-params-before-body-expr?expand=1#diff-acac6ea10e991af0da91633e08b2739f9f9ca0c8f826401b6ba829914d0806f2), where both the params and expression encounter errors in translating consts to patterns. This change puts the errors in the order they appear in the source file.
- Guard patterns (#129967) contain expressions, so lowering params containing guard patterns may add more expressions to the THIR. However, there's a check for `-Zunpretty=thir-tree` that the final expression in the THIR corresponds to its value [(link)](c43786c9b7/compiler/rustc_mir_build/src/builder/mod.rs (L453-L455)); lowering params last would break this. As an alternative way to get guard patterns to work, I think the pretty-printer could use the expression returned by `thir_body` and the check could be removed or changed (#141357).
incorrectly prefer builtin `dyn` impls :3
This makes #57893 slightly more exploitable with the new solver. It's still strictly better than the old solver and the underlying unsoundness persists in the new one even without this preference.
Properly fixing #57893 is something we've been looking at more deeply recently and discussed at the [Types Meetup during the All-Hands](https://hackmd.io/rz-4ghMzTb2wXOkdLKHaHw#Dyn-traits). Whatever approach we'll end up deciding on will likely require a fairly long transition period and some significant further design work. This should not block `-Znext-solver`.
fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/183
r? `@compiler-errors` cc `@rust-lang/types`
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
only resolve top-level guard patterns' guards once
We resolve guard patterns' guards in `resolve_pattern_inner`, so to avoid resolving them multiple times, we must avoid doing so earlier. To accomplish this, `LateResolutionVisitor::visit_pat` contains a case for guard patterns that avoids visiting their guards while walking patterns.
This PR fixes#141265, which was due to `visit::walk_pat` being used instead; this meant guards at the top level of a pattern would be visited twice. e.g. it would ICE on `for x if x in [] {}`, but not `for (x if x) in [] {}`. `visit_pat` was already used for the guard pattern in the second example, on account of the top-level pattern being parens.
