`InferCtxt::next_{ty,const}_var*` all take an origin, but the
`param_def_id` is almost always `None`. This commit changes them to just
take a `Span` and build the origin within the method, and adds new
methods for the rare cases where `param_def_id` might not be `None`.
This avoids a lot of tedious origin building.
Specifically:
- next_ty_var{,_id_in_universe,_in_universe}: now take `Span` instead of
`TypeVariableOrigin`
- next_ty_var_with_origin: added
- next_const_var{,_in_universe}: takes Span instead of ConstVariableOrigin
- next_const_var_with_origin: added
- next_region_var, next_region_var_in_universe: these are unchanged,
still take RegionVariableOrigin
The API inconsistency (ty/const vs region) seems worth it for the
large conciseness improvements.
Don't ICE when we cannot eval a const to a valtree in the new solver
Use `const_eval_resolve` instead of `try_const_eval_resolve` because naming aside, the former doesn't ICE when a value can't be evaluated to a valtree.
r? lcnr
borrowck: prepopulate opaque storage more eagerly
otherwise we ICE due to ambiguity when normalizing while computing implied bounds.
r? ``@compiler-errors``
Record impl args in the proof tree in new solver
Rather than rematching them during select.
Also use `ImplSource::Param` instead of `ImplSource::Builtin` for alias-bound candidates, so we don't ICE in `Instance::resolve`.
r? lcnr
Don't consider candidates with no failing where clauses when refining obligation causes in new solver
Improves error messages when we have param-env candidates that don't deeply unify (i.e. after alias-bounds).
r? lcnr
Prefer lower vtable candidates in select in new solver
Also, adjust the select visitor to only winnow when the *parent* goal is `Certainty::Yes`. This means that we won't winnow in cases when we have any ambiguous inference guidance from two candidates.
r? lcnr
Implement `do_not_recommend` in the new solver
Put the test into `diagnostic_namespace` test folder even though it's not in the diagnostic namespace, because it should be soon.
r? lcnr
cc `@weiznich`
Use a proof tree visitor to refine the `Obligation` for error reporting in new solver
With the magic of `ProofTreeVisitor`, we can close the gap that we have on `ObligationCause`s being not as descriptive in the new trait solver.
r? lcnr
Needs some work and obviously documentation.
Rewrite select (in the new solver) to use a `ProofTreeVisitor`
We can use a proof tree visitor rather than collecting and recomputing all the nested goals ourselves.
Based on #124415
Remove many `#[macro_use] extern crate foo` items
This requires the addition of more `use` items, which often make the code more verbose. But they also make the code easier to read, because `#[macro_use]` obscures where macros are defined.
r? `@fee1-dead`
`obligations_for_self_ty`: use `ProofTreeVisitor` for nested goals
As always, dealing with proof trees continues to be a hacked together mess. After this PR and #124380 the only remaining blocker for core is https://github.com/rust-lang/trait-system-refactor-initiative/issues/90. There is also a `ProofTreeVisitor` issue causing an ICE when compiling `alloc` which I will handle in a separate PR. This issue likely affects coherence diagnostics more generally.
The core idea is to extend the proof tree visitor to support visiting nested candidates without using a `probe`. We then simply recurse into nested candidates if they are the only potentially applicable candidate for a given goal and check whether the self type matches the expected one.
For that to work, we need to improve `CanonicalState` to also handle unconstrained inference variables created inside of the trait solver. This is done by extending the `var_values` of `CanoncalState` with each fresh inference variables. Furthermore, we also store the state of all inference variables at the end of each probe. When recursing into `InspectCandidates` we then unify the values of all these states.
r? `@compiler-errors`
