Register obligations during path inference
Fixes#14635
When we infer path expressions that resolve to some generic item, we need to consider their generic bounds. For example, when we resolve a path `Into::into` to `fn into<?0, ?1>` (note that `?0` is the self type of trait ref), we should register an obligation `?0: Into<?1>` or else their relationship would be lost.
Relevant part in rustc is [`add_required_obligations_with_code()`] that's called in [`instantiate_value_path()`].
[`instantiate_value_path()`]: 3462f79e94/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs (L1052)
[`add_required_obligations_with_code()`]: 3462f79e94/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs (L1411)
Fix explicit deref problems in closure capture
fix the `need-mut` part of #14562
Perhaps surprisingly, it wasn't unique immutable borrow. The code still doesn't emit any of them, and I think those won't happen in edition 2021 (which is currently the only thing implemented), since we always capture `&mut *x` instead of `&mut x`. But I'm not very sure about it.
Normalize associated types in paths in expressions
Part of #14393
When we resolve paths in expressions (either path expressions or paths in struct expressions), there's a need of projection normalization, which `TyLoweringContext` cannot do on its own. We've been properly applying normalization for paths in struct expressions without type anchor, but not for others:
```rust
enum E {
S { v: i32 }
Empty,
}
impl Foo for Bar {
type Assoc = E;
fn foo() {
let _ = Self::Assoc::S { v: 42 }; // path in struct expr without type anchor; we already support this
let _ = <Self>::Assoc::S { v: 42 }; // path in struct expr with type anchor; resolves with this PR
let _ = Self::Assoc::Empty; // path expr; resolves with this PR
}
}
```
With this PR we correctly resolve the whole path, but we need some more tweaks in HIR and/or IDE layers to properly resolve a qualifier (prefix) of such paths and provide IDE features that are pointed out in #14393 to be currently broken.
MIR episode 3
This PR adds lowering for try operator and overloaded dereference, and adds evaluating support for function pointers and trait objects. It also adds a flag to `analysis-stats` to show percentage of functions that it fails to emit mir for them, which is currently `20%` (which is somehow lying, as most of the supported `80%` are tests). The most offenders are closure (1975 items) and overloaded index (415 items). I will try to add overloaded index before monday to have it in this PR, and tackle the closure in the next episode.
internal: Rename `hir::diagnostics::MissingMatchArms.match_expr` field
`hir::diagnostics::MissingMatchArms.match_expr` had confusing name: it is pointing to scrutinee expression. Renamed to `scrutinee_expr` and used better fitting type for it.
Also small refactorings/cleanup.
internal: Re-use the resolver in `InferenceContext` instead of rebuilding it whenever needed
This reduced inference time on my local build by roughly ~1 sec (out of like 60)
Handle trait alias definitions
Part of #2773
This PR adds a bunch of structs and enum variants for trait aliases. Trait aliases should be handled as an independent item because they are semantically distinct from traits.
I basically started by adding `TraitAlias{Id, Loc}` to `hir_def::item_tree` and iterated adding necessary stuffs until compiler stopped complaining what's missing. Let me know if there's still anything I need to add.
I'm opening up this PR for early review and stuff. I'm planning to add tests for IDE functionalities in this PR, but not type-related support, for which I put FIXME notes.
Beginning of MIR
This pull request introduces the initial implementation of MIR lowering and interpreting in Rust Analyzer.
The implementation of MIR has potential to bring several benefits:
- Executing a unit test without compiling it: This is my main goal. It can be useful for quickly testing code changes and print-debugging unit tests without the need for a full compilation (ideally in almost zero time, similar to languages like python and js). There is a probability that it goes nowhere, it might become slower than rustc, or it might need some unreasonable amount of memory, or we may fail to support a common pattern/function that make it unusable for most of the codes.
- Constant evaluation: MIR allows for easier and more correct constant evaluation, on par with rustc. If r-a wants to fully support the type system, it needs full const eval, which means arbitrary code execution, which needs MIR or something similar.
- Supporting more diagnostics: MIR can be used to detect errors, most famously borrow checker and lifetime errors, but also mutability errors and uninitialized variables, which can be difficult/impossible to detect in HIR.
- Lowering closures: With MIR we can find out closure capture modes, which is useful in detecting if a closure implements the `FnMut` or `Fn` traits, and calculating its size and data layout.
But the current PR implements no diagnostics and doesn't support closures. About const eval, I removed the old const eval code and it now uses the mir interpreter. Everything that is supported in stable rustc is either implemented or is super easy to implement. About interpreting unit tests, I added an experimental config, disabled by default, that shows a `pass` or `fail` on hover of unit tests (ideally it should be a button similar to `Run test` button, but I didn't figured out how to add them). Currently, no real world test works, due to missing features including closures, heap allocation, `dyn Trait` and ... so at this point it is only useful for me selecting what to implement next.
The implementation of MIR is based on the design of rustc, the data structures are almost copy paste (so it should be easy to migrate it to a possible future stable-mir), but the lowering and interpreting code is from me.
(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
