resolve: Simplify collection of traits in scope
"Traits in scope" for a given location are collected by walking all scopes in type namespace, collecting traits in them and pruning traits that don't have an associated item with the given name and namespace.
Previously we tried to prune traits using some kind of hygienic resolution for associated items, but that was complex and likely incorrect, e.g. in #80762 correction to visibilites of trait items caused some traits to not be in scope anymore.
I previously had some comments and concerns about this in https://github.com/rust-lang/rust/pull/65351.
In this PR we are doing some much simpler pruning based on `Symbol` and `Namespace` comparisons, it should be enough to throw away 99.9% of unnecessary traits.
It is not necessary for pruning to be precise because for trait aliases, for example, we don't do any pruning at all, and precise hygienic resolution for associated items needs to be done in typeck anyway.
The somewhat unexpected effect is that trait imports introduced by macros 2.0 now bring traits into scope due to the removed hygienic check on associated item names.
I'm not sure whether it is desirable or not, but I think it's acceptable for now.
The old check was certainly incorrect because macros 2.0 did bring trait aliases into scope.
If doing this is not desirable, then we should come up with some other way to avoid bringing traits from macros 2.0 into scope, that would accommodate for trait aliases as well.
---
The PR also contains a couple of pure refactorings
- Scope walk is done by using `visit_scopes` instead of a hand-rolled version.
- Code is restructured to accomodate for rustdoc that also wants to query traits in scope, but doesn't want to filter them by associated items at all.
r? ```@matthewjasper```
resolve: Simplify built-in macro table
We don't use full `SyntaxExtension`s from the table, only `SyntaxExtensionKind`s, and `Ident` in `register_builtin_macro` always had dummy span. This PR removes unnecessary data from the table and related function signatures.
Noticed when reviewing #80850.
resolve: Scope visiting doesn't need an `Ident`
Resolution scope visitor (`fn visit_scopes`) currently takes an `Ident` parameter, but it doesn't need a full identifier, or even its span, it only needs the `SyntaxContext` part.
The `SyntaxContext` part is necessary because scope visitor has to jump to macro definition sites, so it has to be directed by macro expansion information somehow.
I think it's clearer to pass only the necessary part.
Yes, usually visiting happens as a part of an identifier resolution, but in cases like collecting traits in scope (#80765) or collecting typo suggestions that's not the case.
r? `@matthewjasper`
Allow #[rustc_builtin_macro = "name"]
This adds the option of specifying the name of a builtin macro in the `#[rustc_builtin_macro]` attribute: `#[rustc_builtin_macro = "name"]`.
This makes it possible to have both `std::panic!` and `core::panic!` as a builtin macro, by using different builtin macro names for each. This is needed to implement the edition-specific behaviour of the panic macros of RFC 3007.
Also removes `SyntaxExtension::is_derive_copy`, as the macro name (e.g. `sym::Copy`) is now tracked and provides that information directly.
r? ``@petrochenkov``
This makes it possible to have both std::panic and core::panic as a
builtin macro, by using different builtin macro names for each.
Also removes SyntaxExtension::is_derive_copy, as the macro name (e.g.
sym::Copy) is now tracked and provides that information directly.
On structured suggestion for `let` -> `const` and `const` -> `let`, use
a proper `Span` and update tests to check the correct application.
Follow up to #80012.
* Rename `ModuleData.normal_ancestor_id` to `nearest_parent_mod`
`normal_ancestor_id` is a very confusing name if you don't already
understand what it means. Adding docs helps, but using a clearer and
more obvious name is also important.
* Rename `Resolver::nearest_mod_parent` to `nearest_parent_mod`
* Add more docs
remove unused return type of dropck::check_drop_obligations()
don't wrap return type in Option in get_macro_by_def_id() since we would always return Some(..)
remove redundant return type of back::write::optimize()
don't Option-wrap return type of compute_type_parameters() since we always return Some(..)
don't return empty Result in assemble_generator_candidates()
don't return empty Result in assemble_closure_candidates()
don't return empty result in assemble_fn_pointer_candidates()
don't return empty result in assemble_candidates_from_impls()
don't return empty result in assemble_candidates_from_auto_impls()
don't return emtpy result in assemble_candidates_for_trait_alias()
don't return empty result in assemble_builtin_bound_candidates()
don't return empty results in assemble_extension_candidates_for_traits_in_scope() and assemble_extension_candidates_for_trait()
remove redundant wrapping of return type of StripItem::strip() since it always returns Some(..)
remove unused return type of assemble_extension_candidates_for_all_traits()
Previously, this code treated enum fields' visibility as if they were
struct fields. However, that's not correct because the visibility of a
struct field with `ast::VisibilityKind::Inherited` is private to the
module it's defined in, whereas the visibility of an *enum* field with
`ast::VisibilityKind::Inherited` is the visibility of the enum it
belongs to.
Use `DroplessArena` where we know the type doesn't need drop
This PR uses a single `DroplessArena` in resolve instead of three separate `TypedArena`s.
`DroplessArena` checks that the type indeed doesn't need drop, so in case the types change, this will result in visible failures.
* Change error message for type param in a const expression when using
min_const_generics
* Change ParamInNonTrivialAnonConst to contain an extra bool used for
distinguishing whether the passed-in symbol is a type or a value.
Give better diagnostic when using a private tuple struct constructor
Fixes#75907
Some notes:
1. This required some deep changes, including removing a Copy impl for PatKind. If some tests fail, I would still appreciate review on the overall approach
2. this only works with basic patterns (no wildcards for example), and fails if there is any problems getting the visibility of the fields (i am not sure what the failure that can happen in resolve_visibility_speculative, but we check the length of our fields in both cases against each other, so if anything goes wrong, we fall back to the worse error. This could be extended to more patterns
3. this does not yet deal with #75906, but I believe it will be similar
4. let me know if you want more tests
5. doesn't yet at the suggestion that `@yoshuawuyts` suggested at the end of their issue, but that could be added relatively easily (i believe)
Improve unresolved use error message
"use of undeclared type or module `foo`" doesn't mention that it could be a crate.
This error can happen when users forget to add a dependency to `Cargo.toml`, so I think it's important to mention that it could be a missing crate.
I've used a heuristic based on Rust's naming conventions. It complains about an unknown type if the ident starts with an upper-case letter, and crate or module otherwise. It seems to work very well. The expanded error help covers both an unknown type and a missing crate case.
Previously, this would say no such macro existed, but this was
misleading, since the macro _did_ exist, it was just already seen.
- Say where the macro was previously defined
- Add long-form error message
