Clean up the eager formatting API
For https://github.com/rust-lang/rust/issues/151366#event-22181360642
Previously eager formatting worked by throwing the arguments into a diag, formatting, then removing the args again. This is ugly so instead we now just do the formatting completely separately.
This PR has nice commits, so I recommend reviewing commit by commit.
r? @GuillaumeGomez
Remove unhelpful hint from trivial bound errors
The `= help: see issue #48214` hint on trivial bound errors isn't useful, most users hitting these errors aren't trying to use the `trivial_bounds` feature. The `disabled_nightly_features` call already handles suggesting the feature gate on nightly.
Closesrust-lang/rust#152872
refactor(mgca): Change `DefKind::Const` and `DefKind::AssocConst` to have a `is_type_const` flag
Addresses rust-lang/rust#152940
- Changed `DefKind::Const` and `DefKind::AssocConst` to have a `is_type_const` flag.
- changed `is_type_const` query to check for this flag
- removed `is_rhs_type_const` query
r? @BoxyUwU
* refactor: add `is_type_const` flag to `DefKind::Const` and `AssocConst`
* refactor(cleanup) remove the `rhs_is_type_const` query
* style: fix formatting
* refactor: refactor stuff in librustdoc for new Const and AssocConst
* refactor: refactor clippy for the changes
* chore: formatting
* fix: fix test
* fix: fix suggestions
* Update context.rs
Co-authored-by: Boxy <rust@boxyuwu.dev>
* changed AssocKind::Const to store data about being a type const
Don't allow subdiagnostic to use variables from their parent
Tangentially related to https://github.com/rust-lang/rust/issues/151366
This is PR 1/2 for structured diagnostics, will do the unstructured ones next. After the second PR I will be able to remove some code that should compensate for this PR being positive.
Regardless of this PR having a positive diff, I feel that subdiagnostics being able to use variables from their parent is very confusing, so this is for the better,.
r? @jdonszelmann
add field representing types
*[View all comments](https://triagebot.infra.rust-lang.org/gh-comments/rust-lang/rust/pull/152730)*
> [!NOTE]
> This is a rewrite of #146307 by using a lang item instead of a custom `TyKind`. We still need a `hir::TyKind::FieldOf` variant, because resolving the field name cannot be done before HIR construction. The advantage of doing it this way is that we don't need to make any changes to types after HIR (including symbol mangling). At the very beginning of this feature implementation, I tried to do it using a lang item, but then quickly abandoned the approach, because at that time I was still intending to support nested fields.
Here is a [range-diff](https://triagebot.infra.rust-lang.org/gh-range-diff/rust-lang/rust/605f49b27444a738ea4032cb77e3bdc4eb811bab..d15f5052095b3549111854a2555dd7026b0a729e/605f49b27444a738ea4032cb77e3bdc4eb811bab..f5f42d1e03495dbaa23671c46b15fccddeb3492f) between the two PRs
---
# Add Field Representing Types (FRTs)
This PR implements the first step of the field projection lang experiment (Tracking Issue: rust-lang/rust#145383). Field representing types (FRTs) are a new kind of type. They can be named through the use of the `field_of!` macro with the first argument being the type and the second the name of the field (or variant and field in the case of an enum). No nested fields are supported.
FRTs natively implement the `Field` trait that's also added in this PR. It exposes information about the field such as the type of the field, the type of the base (i.e. the type that contains the field) and the offset within that base type. Only fields of non-packed structs are supported, fields of enums an unions have unique types for each field, but those do not implement the `Field` trait.
This PR was created in collaboration with @dingxiangfei2009, it wouldn't have been possible without him, so huge thanks for mentoring me!
I updated my library solution for field projections to use the FRTs from `core` instead of creating my own using the hash of the name of the field. See the [Rust-for-Linux/field-projection `lang-experiment` branch](https://github.com/Rust-for-Linux/field-projection/tree/lang-experiment).
## API added to `core::field`
```rust
pub unsafe trait Field {
type Base;
type Type;
const OFFSET: usize;
}
pub macro field_of($Container:ty, $($fields:expr)+ $(,)?);
```
Along with a perma-unstable type that the compiler uses in the expansion of the macro:
```rust
#[unstable(feature = "field_representing_type_raw", issue = "none")]
pub struct FieldRepresentingType<T: ?Sized, const VARIANT: u32, const FIELD: u32> {
_phantom: PhantomData<T>,
}
```
## Explanation of Field Representing Types (FRTs)
FRTs are used for compile-time & trait-level reflection for fields of structs & tuples. Each struct & tuple has a unique compiler-generated type nameable through the `field_of!` macro. This type natively contains information about the field such as the outermost container, type of the field and its offset. Users may implement additional traits on these types in order to record custom information (for example a crate may define a [`PinnableField` trait](https://github.com/Rust-for-Linux/field-projection/blob/lang-experiment/src/marker.rs#L9-L23) that records whether the field is structurally pinned).
They are the foundation of field projections, a general operation that's generic over the fields of a struct. This genericism needs to be expressible in the trait system. FRTs make this possible, since an operation generic over fields can just be a function with a generic parameter `F: Field`.
> [!NOTE]
> The approach of field projections has changed considerably since this PR was opened. In the end we might not need FRTs, so this API is highly experimental.
FRTs should act as though they were defined as `struct MyStruct_my_field<StructGenerics>;` next to the struct. So it should be local to the crate defining the struct so that one can implement any trait for the FRT from that crate. The `Field` traits should be implemented by the compiler & populated with correct information (`unsafe` code needs to be able to rely on them being correct).
## TODOs
There are some `FIXME(FRTs)` scattered around the code:
- Diagnostics for `field_of!` can be improved
- `tests/ui/field_representing_types/nonexistent.rs`
- `tests/ui/field_representing_types/non-struct.rs`
- `tests/ui/field_representing_types/offset.rs`
- `tests/ui/field_representing_types/not-field-if-packed.rs`
- `tests/ui/field_representing_types/invalid.rs`
- Simple type alias already seem to work, but might need some extra work in `compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs`
r? @oli-obk
Avoid duplicate `requirement` diag args in `RegionOriginNote`
Fixesrust-lang/rust#143872
`RegionOriginNote::WithRequirement` can be emitted multiple times for one
diagnostic. I fixed the ICE by scoping per note fluent args in `RegionOriginNote::WithRequirement` with `store_args` and `restore_args`.
mGCA: Enforce WF element types for array valtrees
Fixesrust-lang/rust#152125
Extends WellFormedness checking for const generics to validate that array element types in ValTrees match the declared element type.
### Problem
Before commit, this would have incorrectly compiled
``` rust
#![feature(adt_const_params, min_generic_const_args)]
use std::marker::ConstParamTy;
#[derive(Eq, PartialEq, ConstParamTy)]
struct Foo;
struct Bar;
fn foo<const N: [Foo; 1]>() {}
fn main() {
foo::<{ [Bar] }>();
}
```
### Solution
Added a `ty::Array` arm to checking WellFormedness (similar to the existing `ty::Tuple` arm from rust-lang/rust#150713) which creates `ConstArgHasType` obligations for each array element, ensuring they match the array's declared element type.
I attempted to combine the `Tuple` and `Array` arms into a single arm, but this proved difficult due to pattern matching limitations, and the separate arm is more readable anyway.
### Tests
Added UI test which verifies that the type mismatch is now properly caught, and also returns an appropriate test message
r? @BoxyUwU
Remove `impl IntoQueryParam<P> for &'a P`.
`IntoQueryParam` is a trait that lets query callers be a bit sloppy with the passed-in key.
- Types similar to `DefId` will be auto-converted to `DefId`. Likewise for `LocalDefId`.
- Reference types will be auto-derefed.
The auto-conversion is genuinely useful; the auto-derefing much less so. In practice it's only used for passing `&DefId` to queries that accept `DefId`, which is an anti-pattern because `DefId` is marked with `#[rustc_pass_by_value]`.
This commit removes the auto-deref impl and makes the necessary sigil adjustments. (I generally avoid using `*` to deref manually at call sites, preferring to deref via `&` in patterns or via `*` in match expressions. Mostly because that way a single deref often covers multiple call sites.)
r? @cjgillot
`IntoQueryParam` is a trait that lets query callers be a bit sloppy with
the passed-in key.
- Types similar to `DefId` will be auto-converted to `DefId`. Likewise
for `LocalDefId`.
- Reference types will be auto-derefed.
The auto-conversion is genuinely useful; the auto-derefing much less so.
In practice it's only used for passing `&DefId` to queries that accept
`DefId`, which is an anti-pattern because `DefId` is marked with
`#[rustc_pass_by_value]`.
This commit removes the auto-deref impl and makes the necessary sigil
adjustments. (I generally avoid using `*` to deref manually at call
sites, preferring to deref via `&` in patterns or via `*` in match
expressions. Mostly because that way a single deref often covers
multiple call sites.)
Jonathan Brouwer