Implement non-const `Destruct` trait in new solver
Makes it so that we can call stdlib methods like `Option::map` in **non-const** environments, since *many* stdlib methods have `Destruct` bounds 😅
This doesn't bother to implement `const Destruct` yet, but it shouldn't be too hard to do so. Just didn't bother since we already don't have much support for const traits in the new solver anyways. I'd be happy to add skeleton support for `const Destruct`, though, if the reviewer desires.
Rollup of 9 pull requests
Successful merges:
- #108629 (rustdoc: add support for type filters in arguments and generics)
- #108924 (panic_immediate_abort requires abort as a panic strategy)
- #108961 (Refine error spans for const args in hir typeck)
- #108986 (sync LVI tests)
- #109142 (Add block-based mutex unlocking example)
- #109368 (fix typo in the creation of OpenOption for RustyHermit)
- #109493 (Return nested obligations from canonical response var unification)
- #109515 (Add AixLinker to support linking on AIX)
- #109536 (resolve: Rename some cstore methods to match queries and add comments)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Return nested obligations from canonical response var unification
Handle alias-eq obligations being emitted from `instantiate_and_apply_query_response` in:
* `EvalCtxt` - by processing the nested obligations in the next loop by `new_goals`
* `FulfillCtxt` - by adding the nested obligations to the fulfillment's pending obligations
* `InferCtxt::evaluate_obligation` - ~~by returning `EvaluationResult::EvaluatedToAmbig` (boo 👎, see the FIXME)~~ same behavior as above, since we use fulfillment and `select_where_possible`
The only one that's truly sketchy is `evaluate_obligation`, but it's not hard to modify this behavior moving forward.
From #109037, I think a smaller repro could be crafted if I were smarter, but I am not, so I just took this from #105878.
r? `@lcnr` cc `@BoxyUwU`
Refine error spans for const args in hir typeck
Improve just a couple of error messages having to do with mismatched consts.
r? `@ghost` i'll put this up when the dependent commits are merged
Rollup of 7 pull requests
Successful merges:
- #108541 (Suppress `opaque_hidden_inferred_bound` for nested RPITs)
- #109137 (resolve: Querify most cstore access methods (subset 2))
- #109380 (add `known-bug` test for unsoundness issue)
- #109462 (Make alias-eq have a relation direction (and rename it to alias-relate))
- #109475 (Simpler checked shifts in MIR building)
- #109504 (Stabilize `arc_into_inner` and `rc_into_inner`.)
- #109506 (make param bound vars visibly bound vars with -Zverbose)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Make alias-eq have a relation direction (and rename it to alias-relate)
Emitting an "alias-eq" is too strict in some situations, since we don't always want strict equality between a projection and rigid ty. Adds a relation direction.
* I could probably just reuse this [`RelationDir`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/combine/enum.RelationDir.html) -- happy to uplift that struct into middle and use that instead, but I didn't feel compelled to... 🤷
* Some of the matching in `compute_alias_relate_goal` is a bit verbose -- I guess I could simplify it by using [`At::relate`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/at/struct.At.html#method.relate) and mapping the relation-dir to a variance.
* Alternatively, I coulld simplify things by making more helper functions on `EvalCtxt` (e.g. `EvalCtxt::relate_with_direction(T, T)` that also does the nested goal registration). No preference.
r? ```@lcnr``` cc ```@BoxyUwU``` though boxy can claim it if she wants
NOTE: first commit is all the changes, the second is just renaming stuff
new solver cleanup + implement coherence
the cleanup:
- change `Certainty::unify_and` to consider ambig + overflow to be ambig
- rename `trait_candidate_should_be_dropped_in_favor_of` to `candidate_should_be_dropped_in_favor_of`
- remove outdated fixme
For coherence I mostly just add an ambiguous candidate if the current trait ref is unknowable. I am doing the same for reservation impl where I also just add an ambiguous candidate.
a general type system cleanup
removes the helper functions `traits::fully_solve_X` as they add more complexity then they are worth. It's confusing which of these helpers should be used in which context.
changes the way we deal with overflow to always add depth in `evaluate_predicates_recursively`. It may make sense to actually fully transition to not have `recursion_depth` on obligations but that's probably a bit too much for this PR.
also removes some other small - and imo unnecessary - helpers.
r? types
Do not suggest bounds restrictions for synthesized RPITITs
Before this PR we were getting ...
```
warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> tests/ui/async-await/in-trait/missing-send-bound.rs:5:12
|
5 | #![feature(async_fn_in_trait)]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
= note: `#[warn(incomplete_features)]` on by default
error: future cannot be sent between threads safely
--> tests/ui/async-await/in-trait/missing-send-bound.rs:17:20
|
17 | assert_is_send(test::<T>());
| ^^^^^^^^^^^ future returned by `test` is not `Send`
|
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `impl Future<Output = ()>`
note: future is not `Send` as it awaits another future which is not `Send`
--> tests/ui/async-await/in-trait/missing-send-bound.rs:13:5
|
13 | T::bar().await;
| ^^^^^^^^ await occurs here on type `impl Future<Output = ()>`, which is not `Send`
note: required by a bound in `assert_is_send`
--> tests/ui/async-await/in-trait/missing-send-bound.rs:21:27
|
21 | fn assert_is_send(_: impl Send) {}
| ^^^^ required by this bound in `assert_is_send`
help: consider further restricting the associated type
|
16 | fn test2<T: Foo>() where impl Future<Output = ()>: Send {
| ++++++++++++++++++++++++++++++++++++
error: aborting due to previous error; 1 warning emitted
```
and we want this output ...
```
warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
--> $DIR/missing-send-bound.rs:5:12
|
LL | #![feature(async_fn_in_trait)]
| ^^^^^^^^^^^^^^^^^
|
= note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
= note: `#[warn(incomplete_features)]` on by default
error: future cannot be sent between threads safely
--> $DIR/missing-send-bound.rs:17:20
|
LL | assert_is_send(test::<T>());
| ^^^^^^^^^^^ future returned by `test` is not `Send`
|
= help: within `impl Future<Output = ()>`, the trait `Send` is not implemented for `impl Future<Output = ()>`
note: future is not `Send` as it awaits another future which is not `Send`
--> $DIR/missing-send-bound.rs:13:5
|
LL | T::bar().await;
| ^^^^^^^^ await occurs here on type `impl Future<Output = ()>`, which is not `Send`
note: required by a bound in `assert_is_send`
--> $DIR/missing-send-bound.rs:21:27
|
LL | fn assert_is_send(_: impl Send) {}
| ^^^^ required by this bound in `assert_is_send`
error: aborting due to previous error; 1 warning emitted
```
r? `@compiler-errors`
Only implement Fn* traits for extern "Rust" safe function pointers and items
Since calling the function via an `Fn` trait will assume `extern "Rust"` ABI and not do any safety checks, only safe `extern "Rust"` function can implement the `Fn` traits. This syncs the logic between the old solver and the new solver.
r? `@compiler-errors`
Constrain const vars to error if const types are mismatched
When equating two consts of different types, if either are const variables, constrain them to the correct const error kind.
This helps us avoid "successfully" matching a const against an impl signature but leaving unconstrained const vars, which will lead to incremental ICEs when we call const-eval queries during const projection.
Fixes#109296
The second commit in the stack fixes a regression in the first commit where we end up mentioning `[const error]` in an impl overlap error message. I think the error message changes for the better, but I could implement alternative strategies to avoid this without delaying the overlap error message...
r? `@BoxyUwU`
new solver: make all goal evaluation able to be automatically rerun
It is generally wrong to call `evaluate_goal` multiple times or `evaluate_goal` and `evaluate_all` for the same `QueryResult` without correctly handling rerunning the goals when inference makes progress. Not doing so will result in the assertion in `evaluate_goal` firing because rerunning the goal will lead to a more accurate `QueryResult`.
Currently there are lots of places that get this wrong and generally it is complex and error prone to handle correctly everywhere. This PR introduces a way to add goals to the `EvalCtxt` and then run all the added goals in a loop so that `evaluate_goal`/`evaluate_all` is not necessary to call manually.
There are a few complications for making everything work "right":
1. the `normalizes-to` hack that replaces the rhs with an unconstrained infer var requires special casing in the new `try_evaluate_added_goals` function similar to how `evaluate_goal`'s assertion special cases that hack.
2. `assemble_candidates_after_normalizing_self_ty`'s normalization step needs to be reran for each candidate otherwise the found candidates will potentially get a more accurate `QueryResult` when rerunning the projection/trait goal which can effect the `QueryResult` of the projection/trait goal.
This is implemented via `EvalCtxt::probe`'s closure's `EvalCtxt` inheriting the added goals of the `EvalCtxt` that `probe` is called on, allowing us to add goals in a probe, and then enter a nested probe for each candidate and evaluate added goals which include the normalization step's goals.
I made `make_canonical_response` evaluate added goals so that it will be hard to mess up the impl of the solver by forgetting to evaluate added goals. Right now the only way to mess this up would be to call `response_no_constraints` (which from the name is obviously weird).
The visibility of `evaluate_goal` means that it can be called from various `compute_x_goal` or candidate assembly functions, this is generally wrong and we should never call `evaluate_goal` manually, instead we should be calling `add_goal`/`add_goals`. This is solved by moving `evaluate_goal` `evaluate_canonical_goal` and `compute_goal` into `eval_ctxt`'s module and making them private so they cannot be called from elsewhere, forcing people to call `add_goal/s` and `evaluate_added_goals_and_make_canonical_resposne`/`try_evaluate_added_goals`
---
Other changes:
- removed the `&& false` that was introduced to the assertion in `evaluate_goal` in #108839
- remove a `!self.did_overflow()` requirement in `search_graph.is_empty()` which causes goals that overflow to ICE
- made `EvalCtxt::eq` take `&mut self` and add all the nested goals via `add_goals` instead of returning them as 99% of call sites just immediately called `EvalCtxt::add_goals` manually.
r? `````@lcnr`````
- only borrow the refcell once per loop
- avoid complex matches to reduce branch paths in the hot loop
- use a by-ref fast path that avoids mutations at the expense of having false negatives
Install projection from RPITIT to default trait method opaque correctly
1. For new lowering strategy `-Zlower-impl-trait-in-trait-to-assoc-ty`, install the correct default trait method projection predicates (RPITIT -> opaque). This makes default trait body tests pass!
2. Fix two WF-checking bugs -- first, we want to make sure that we're always looking for an opaque type in `check_return_position_impl_trait_in_trait_bounds`. That's because the RPITIT projections are normalized to opaques during wfcheck. Second, fix RPITIT's param-envs by not adding the projection predicates that we install on trait methods to make default RPITITs work -- I left a comment why.
3. Also, just a small drive-by for `rustc_on_unimplemented`. Not sure if it affects any tests, but can't hurt.
r? ````@spastorino,```` based off of #109140
Remove box expressions from HIR
After #108516, `#[rustc_box]` is used at HIR->THIR lowering and this is no longer emitted, so it can be removed.
This is based on top of #108471 to help with conflicts, so 43490488ccacd1a822e9c621f5ed6fca99959a0b is the only relevant commit (sorry for all the duplicated pings!)
````@rustbot```` label +S-blocked
Some cleanups in our normalization logic
Changed a match to be exhaustive and deduplicated some code.
r? ```@compiler-errors```
this pulls out the uncontroversial part of https://github.com/rust-lang/rust/pull/108860
make `define_opaque_types` fully explicit
based on the idea of #108389. Moved `define_opaque_types` into the actual operations, e.g. `eq`, instead of `infcx.at` because normalization doesn't use `define_opaque_types` and even creates it's own `At` with a different `define_opaque_types` internally.
Somewhat surprisingly, coherence actually relies on `DefineOpaqueTypes::Yes` for soundness which was revealed because I've incorrectly used `DefineOpaqueTypes::No` in `equate_impl_headers`. It feels concerning that even though this is the case, we still sometimes use `DefineOpaqueTypes::No` in coherence. I did not look into this as part of this PR as it is purely changing the structure of the code without changing behavior in any way.
r? ```@oli-obk```
Remove some direct calls to local_def_id_to_hir_id on diagnostics
Was playing with `tests/ui/impl-trait/in-trait/default-body-with-rpit.rs` and was able to remove some ICEs. Still getting ...
```
error[E0277]: `impl Future<Output = Foo::{opaque#0}>` is not a future
--> tests/ui/impl-trait/in-trait/default-body-with-rpit.rs:10:28
|
10 | async fn baz(&self) -> impl Debug {
| ^^^^^^^^^^ `impl Future<Output = Foo::{opaque#0}>` is not a future
|
= help: the trait `Future` is not implemented for `impl Future<Output = Foo::{opaque#0}>`
= note: impl Future<Output = Foo::{opaque#0}> must be a future or must implement `IntoFuture` to be awaited
note: required by a bound in `Foo::{opaque#1}`
--> tests/ui/impl-trait/in-trait/default-body-with-rpit.rs:10:28
|
10 | async fn baz(&self) -> impl Debug {
| ^^^^^^^^^^ required by this bound in `Foo::{opaque#1}`
error[E0277]: the size for values of type `impl Future<Output = Foo::{opaque#0}>` cannot be known at compilation time
--> tests/ui/impl-trait/in-trait/default-body-with-rpit.rs:10:28
|
10 | async fn baz(&self) -> impl Debug {
| ^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `Sized` is not implemented for `impl Future<Output = Foo::{opaque#0}>`
note: required by a bound in `Foo::{opaque#1}`
--> tests/ui/impl-trait/in-trait/default-body-with-rpit.rs:10:28
|
10 | async fn baz(&self) -> impl Debug {
| ^^^^^^^^^^ required by this bound in `Foo::{opaque#1}`
error: internal compiler error: compiler/rustc_hir_typeck/src/closure.rs:724:18: async fn generator return type not an inference variable: Foo::{opaque#1}<'_>
--> tests/ui/impl-trait/in-trait/default-body-with-rpit.rs:10:39
|
10 | async fn baz(&self) -> impl Debug {
| _______________________________________^
11 | | ""
12 | | }
| |_____^
```
But I guess this is a little bit of progress anyway.
This one goes on top of #108700 and #108945
r? `@compiler-errors`
Remove `identity_future` indirection
This was previously needed because the indirection used to hide some unexplained lifetime errors, which it turned out were related to the `min_choice` algorithm.
Removing the indirection also solves a couple of cycle errors, large moves and makes async blocks support the `#[track_caller]`annotation.
Fixes https://github.com/rust-lang/rust/issues/104826.
Add suggestion to diagnostic when user has array but trait wants slice. (rebased)
Rebase of #91314, except for change to multipart suggestion
Resolves#90528
r? ``@compiler-errors`` since you requested the multipart suggestion
tidy: enforce comment blocks to have an even number of backticks
After PR #108694, most unmatched backticks in `compiler/` comments have been eliminated. This PR adds a tidy lint to ensure no new unmatched backticks are added, and either addresses the lint in the remaining instances it found, or allows it.
Very often, backtick containing sections wrap around lines, for example:
```Rust
// This function takes a tuple `(Vec<String>,
// Box<[u8]>)` and transforms it into `Vec<u8>`.
```
The lint is implemented to work on top of blocks, counting each line with a `//` into a block, and counting if there are an odd or even number of backticks in the entire block, instead of looking at just a single line.
This makes it easier to open the messages file while developing on features.
The commit was the result of automatted changes:
for p in compiler/rustc_*; do mv $p/locales/en-US.ftl $p/messages.ftl; rmdir $p/locales; done
for p in compiler/rustc_*; do sed -i "s#\.\./locales/en-US.ftl#../messages.ftl#" $p/src/lib.rs; done
Implement goal caching with the new solver
Maybe it's wrong, idk. Opening mostly for first impressions before I go to sleep.
r? ``@lcnr,`` cc ``@cjgillot``
Don't even try to combine consts with incompatible types
~I left a more detailed explanation for why this fixes this issue in the UI test, but in general, we should not try to unify const infer vars and rigid consts if they have incompatible types. That's because we don't want something like a `ConstArgHasType` predicate to suddenly go from passing to failing, or vice versa, due to a shallow resolve.~
1. Use the `type_of` for a parameter in `try_eval_lit_or_param`, instead of the "expected" type from a `WithOptConstParam` def id.
2. Don't combine consts that have incompatible types.
Fixes#108781
Do not ICE when we have fn pointer `Fn` obligations with bound vars in the self type
We never supported solving `for<'a> fn(&'a ()): Fn(&'a ())` -- I tried to add that support in #104929, but iirc `@lcnr` wanted to support this more generally by eagerly instantiating trait predicate binders with placeholders. That never happened due to blockers in the old solver, but we probably shouldn't ICE in any case.
On the bright side, this passes on the new solver :^)
Emit alias-eq when equating numeric var and projection
This doesn't fix everything having to do with projections and infer vars, but it does fix a common case I saw in HIR typeck.
r? `@lcnr`
Remove `body_def_id` from `Inherited`
We can just use the body id from the obligation cause.
Follow-up to #108945, only my commit is relevant.
r? `@cjgillot` cc `@spastorino`
Rollup of 8 pull requests
Successful merges:
- #108754 (Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous)
- #108759 (1.41.1 supported 32-bit Apple targets)
- #108839 (Canonicalize root var when making response from new solver)
- #108856 (Remove DropAndReplace terminator)
- #108882 (Tweak E0740)
- #108898 (Set `LIBC_CHECK_CFG=1` when building Rust code in bootstrap)
- #108911 (Improve rustdoc-gui/tester.js code a bit)
- #108916 (Remove an unused return value in `rustc_hir_typeck`)
Failed merges:
r? `@ghost`
`@rustbot` modify labels: rollup
Canonicalize root var when making response from new solver
During trait solving, if we equate two inference variables `?0` and `?1` but don't equate them with any rigid types, then `InferCtxt::probe_ty_var` will return `Err` for both of these. The canonicalizer code will then canonicalize the variables independently(!), and the response will not reflect the fact that these two variables have been made equal.
This hinders inference and I also don't think it's sound? I haven't thought too much about it past that, so let's talk about it.
r? ``@lcnr``
Retry `pred_known_to_hold_modulo_regions` with fulfillment if ambiguous
Fixes#108721
The problem here is that when we're checking `is_sized_raw` during codegen on some type that has a lot of opaques in it, something emits several nested obligations that are individually ambiguous, but when processed together in a loop then apply modulo regions. Since the `evaluate_predicates_recursively` inner loop doesn't process predicates until they stop changing, we return `EvaluatedToAmbig`, which makes the sized check return false incorrectly. See:
f15f0ea739/compiler/rustc_trait_selection/src/traits/select/mod.rs (L596-L606)
... Compared to the analogous loop in the new solver:
f15f0ea739/compiler/rustc_trait_selection/src/solve/mod.rs (L481-L512)
To fix this, if we get ambiguous during `pred_known_to_hold_modulo_regions`, just retry the obligation in a fulfillment context.
--
Unfortunately... I don't have a test for this. I've only tested this locally. Pending minimization :/
r? types
Suppress copy impl error when post-normalized type references errors
Suppress spurious errors from the `Copy` impl validity check when fields have bad types *post*-normalization, instead of just pre-normalization.
----
The const-generics test regressed recently due to #107965, cc `````@BoxyUwU.`````
* I think it's because `[_; 0u32]: Copy` now fails to hold because a nested obligation `ConstArgHasType(0u32, usize)` fails.
* It's interesting that `[const_error]` shows up in the type only after normalization, though, but I'm pretty sure that it's due to the evaluate call that happens when normalizing unevaluated consts.
This was previously needed because the indirection used to hide some unexplained lifetime errors, which it turned out were related to the `min_choice` algorithm.
Removing the indirection also solves a couple of cycle errors, large moves and makes async blocks support the `#[track_caller]` annotation.
always resolve to universal regions if possible
`RegionConstraintCollector::opportunistic_resolve_var`, which is used in canonicalization and projection logic, doesn't resolve the region var to an equal universal region. So if we have equated `'static == '1 == '2`, it doesn't resolve `'1` or `'2` to `'static`. Now it does!
Addresses review comment https://github.com/rust-lang/rust/pull/107376#discussion_r1093233687.
r? `@lcnr`
rustc_middle: Remove trait `DefIdTree`
This trait was a way to generalize over both `TyCtxt` and `Resolver`, but now `Resolver` has access to `TyCtxt`, so this trait is no longer necessary.
Don't project specializable RPITIT projection
This effective rejects specialization + RPITIT/AFIT (usages of `impl Trait` in traits) because the implementation is significantly complicated over making regular "default" trait method bodies work.
I have another PR that experimentally fixes all this, but the code may not be worth investing in.
Treat `str` as containing `[u8]` for auto trait purposes
Wanted to gauge ``@rust-lang/lang`` and ``@rust-lang/types`` teams' thoughts on treating `str` as "containing" a `[u8]` slice for auto-trait purposes.
``@dtolnay`` brought this up in https://github.com/rust-lang/rust/issues/13231#issuecomment-1399386472 as a blocker for future `str` type librarification, and I think it's both a valid concern and very easy to fix. I'm interested in actually doing that `str` type librarification (#107939), but this probably should be considered in the mean time regardless of that PR.
r? types for the impl, though this definitely needs an FCP.
(This is a large commit. The changes to
`compiler/rustc_middle/src/ty/context.rs` are the most important ones.)
The current naming scheme is a mess, with a mix of `_intern_`, `intern_`
and `mk_` prefixes, with little consistency. In particular, in many
cases it's easy to use an iterator interner when a (preferable) slice
interner is available.
The guiding principles of the new naming system:
- No `_intern_` prefixes.
- The `intern_` prefix is for internal operations.
- The `mk_` prefix is for external operations.
- For cases where there is a slice interner and an iterator interner,
the former is `mk_foo` and the latter is `mk_foo_from_iter`.
Also, `slice_interners!` and `direct_interners!` can now be `pub` or
non-`pub`, which helps enforce the internal/external operations
division.
It's not perfect, but I think it's a clear improvement.
The following lists show everything that was renamed.
slice_interners
- const_list
- mk_const_list -> mk_const_list_from_iter
- intern_const_list -> mk_const_list
- substs
- mk_substs -> mk_substs_from_iter
- intern_substs -> mk_substs
- check_substs -> check_and_mk_substs (this is a weird one)
- canonical_var_infos
- intern_canonical_var_infos -> mk_canonical_var_infos
- poly_existential_predicates
- mk_poly_existential_predicates -> mk_poly_existential_predicates_from_iter
- intern_poly_existential_predicates -> mk_poly_existential_predicates
- _intern_poly_existential_predicates -> intern_poly_existential_predicates
- predicates
- mk_predicates -> mk_predicates_from_iter
- intern_predicates -> mk_predicates
- _intern_predicates -> intern_predicates
- projs
- intern_projs -> mk_projs
- place_elems
- mk_place_elems -> mk_place_elems_from_iter
- intern_place_elems -> mk_place_elems
- bound_variable_kinds
- mk_bound_variable_kinds -> mk_bound_variable_kinds_from_iter
- intern_bound_variable_kinds -> mk_bound_variable_kinds
direct_interners
- region
- intern_region (unchanged)
- const
- mk_const_internal -> intern_const
- const_allocation
- intern_const_alloc -> mk_const_alloc
- layout
- intern_layout -> mk_layout
- adt_def
- intern_adt_def -> mk_adt_def_from_data (unusual case, hard to avoid)
- alloc_adt_def(!) -> mk_adt_def
- external_constraints
- intern_external_constraints -> mk_external_constraints
Other
- type_list
- mk_type_list -> mk_type_list_from_iter
- intern_type_list -> mk_type_list
- tup
- mk_tup -> mk_tup_from_iter
- intern_tup -> mk_tup
Use `tcx.ty_error_with_guaranteed` in more places, rename variants
1. Use `ty_error_with_guaranteed` more so we don't delay so many span bugs
2. Rename `ty_error_with_guaranteed` to `ty_error`, `ty_error` to `ty_error_misc`. This is to incentivize using the former over the latter in cases where we already are witness to a `ErrorGuaranteed` token.
Second commit is just name replacement, so the first commit can be reviewed on its own with more scrutiny.
Use associated type bounds in some places in the compiler
Use associated type bounds for some nested `impl Trait<Assoc = impl Trait2>` cases. I'm generally keen to introduce new lang features that are more mature into the compiler, but maybe let's see what others think?
Side-note: I was surprised that the only use-cases of nested impl trait in the compiler are just iterator related?!
Remove type-traversal trait aliases
#107924 moved the type traversal (folding and visiting) traits into the type library, but created trait aliases in `rustc_middle` to minimise both the API churn for trait consumers and the arising boilerplate. As mentioned in that PR, an alternative approach of defining subtraits with blanket implementations of the respective supertraits was also considered at that time but was ruled out as not adding much value.
Unfortunately, it has since emerged that rust-analyzer has difficulty with these trait aliases at present, resulting in a degraded contributor experience (see the recent [r-a has become useless](https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/r-a.20has.20become.20useless) topic on the #t-compiler/help Zulip stream).
This PR removes the trait aliases, and accordingly the underlying type library traits are now used directly; they are parameterised by `TyCtxt<'tcx>` rather than just the `'tcx` lifetime, and imports have been updated to reflect the fact that the trait aliases' explicitly named traits are no longer automatically brought into scope. These changes also roll-back the (no-longer required) workarounds to #107747 that were made in b409329c62.
Since this PR is just a find+replace together with the changes necessary for compilation & tidy to pass, it's currently just one mega-commit. Let me know if you'd like it broken up.
r? `@oli-obk`
errors: generate typed identifiers in each crate
Instead of loading the Fluent resources for every crate in `rustc_error_messages`, each crate generates typed identifiers for its own diagnostics and creates a static which are pulled together in the `rustc_driver` crate and provided to the diagnostic emitter.
There are advantages and disadvantages to this change..
#### Advantages
- Changing a diagnostic now only recompiles the crate for that diagnostic and those crates that depend on it, rather than `rustc_error_messages` and all crates thereafter.
- This approach can be used to support first-party crates that want to supply translatable diagnostics (e.g. `rust-lang/thorin` in https://github.com/rust-lang/rust/pull/102612#discussion_r985372582, cc `@JhonnyBillM)`
- We can extend this a little so that tools built using rustc internals (like clippy or rustdoc) can add their own diagnostic resources (much more easily than those resources needing to be available to `rustc_error_messages`)
#### Disadvantages
- Crates can only refer to the diagnostic messages defined in the current crate (or those from dependencies), rather than all diagnostic messages.
- `rustc_driver` (or some other crate we create for this purpose) has to directly depend on *everything* that has error messages.
- It already transitively depended on all these crates.
#### Pending work
- [x] I don't know how to make `rustc_codegen_gcc`'s translated diagnostics work with this approach - because `rustc_driver` can't depend on that crate and so can't get its resources to provide to the diagnostic emission. I don't really know how the alternative codegen backends are actually wired up to the compiler at all.
- [x] Update `triagebot.toml` to track the moved FTL files.
r? `@compiler-errors`
cc #100717
