Add context to "const in pattern" errors #133233
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r? @nnethercote rustbot has assigned @nnethercote. Use |
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Some changes occurred in match checking cc @Nadrieril |
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Centralize emitting an error in `const_to_pat` so that all errors from that evaluating a `const` in a pattern can add addditional information. With this, now point at the `const` item's definition:
```
error[E0158]: constant pattern depends on a generic parameter
--> $DIR/associated-const-type-parameter-pattern.rs:20:9
|
LL | pub trait Foo {
| -------------
LL | const X: EFoo;
| ------------- constant defined here
...
LL | A::X => println!("A::X"),
| ^^^^
```
Silence errors that are implied by the errors in the `const` item definition. Add a primary span label.
Conform to error style guide.
```
error[E0158]: constant pattern depends on a generic parameter, which is not allowed
--> $DIR/associated-const-type-parameter-pattern.rs:20:9
|
LL | pub trait Foo {
| -------------
LL | const X: EFoo;
| ------------- constant defined here
...
LL | pub fn test<A: Foo, B: Foo>(arg: EFoo) {
| - constant depends on this generic param
LL | match arg {
LL | A::X => println!("A::X"),
| ^^^^ `const` depends on a generic parameter
```
- Add primary span labels. - Point at const generic parameter used as pattern. - Point at statics used as pattern. - Point at let bindings used in const pattern.
``` error: trait object `dyn Send` cannot be used in patterns --> $DIR/issue-70972-dyn-trait.rs:6:9 | LL | const F: &'static dyn Send = &7u32; | -------------------------- constant defined here ... LL | F => panic!(), | ^ trait object can't be used in patterns ```
- Point at type that should derive `PartialEq` to be structural.
- Point at manual `impl PartialEq`, explaining that it is not sufficient to be structural.
```
error: constant of non-structural type `MyType` in a pattern
--> $DIR/const-partial_eq-fallback-ice.rs:14:12
|
LL | struct MyType;
| ------------- `MyType` must be annotated with `#[derive(PartialEq)]` to be usable in patterns
...
LL | const CONSTANT: &&MyType = &&MyType;
| ------------------------ constant defined here
...
LL | if let CONSTANT = &&MyType {
| ^^^^^^^^ constant of non-structural type
|
note: the `PartialEq` trait must be derived, manual `impl`s are not sufficient; see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details
--> $DIR/const-partial_eq-fallback-ice.rs:5:1
|
LL | impl PartialEq<usize> for MyType {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Unify wording with the regular non-structural type error.
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…e" error Point at types that need to be marked with `#[derive(PartialEq)]`. We use a visitor to look at a type that isn't structural, looking for all ADTs that don't derive `PartialEq`. These can either be manual `impl PartialEq`s or no `impl` at all, so we differentiate between those two cases to provide more context to the user. We also only point at types and impls from the local crate, otherwise show only a note. ``` error: constant of non-structural type `&[B]` in a pattern --> $DIR/issue-61188-match-slice-forbidden-without-eq.rs:15:9 | LL | struct B(i32); | -------- must be annotated with `#[derive(PartialEq)]` to be usable in patterns LL | LL | const A: &[B] = &[]; | ------------- constant defined here ... LL | A => (), | ^ constant of non-structural type | = note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralPartialEq.html for details ```
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I can take this r? @Nadrieril |
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@Nadrieril review best done per commit. Feel free to say "I've done these N commits, split off the rest". I just felt it was useful to see the end result of all changes on the diagnostics in aggregate, but they don't need to land together, just in order. |
estebank
commented
Nov 21, 2024
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| /// Given a type with type parameters, visit every ADT looking for types that need to | ||
| /// `#[derive(PartialEq)]` to be a structural type. | ||
| fn extend_type_not_partial_eq<'tcx>( |
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- This could also be used for the non-fallthrough case (where the top-level type isn't structural), as the visitor would work for that too.
- We could rework this to not operate on the
Diagdirectly, instead create a newSubdiagnostictype that gets added to theDiagnosticas aVec.
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Each commit addresses specific diagnostics.
constitem, andconstgeneric param definitionconstis being referencedconstitems that already emit a diagnosticPartialEq