Add context to "const in pattern" errors #133233

estebank · 2024-11-20T06:28:39Z

Each commit addresses specific diagnostics.

Add primary span labels
Point at const item, and const generic param definition
Reword messages and notes
Point at generic param through which an associated const is being referenced
Silence const in pattern with evaluation errors when they come from const items that already emit a diagnostic
On non-structural type in const used as pattern, point at the type that should derive PartialEq

rustbot · 2024-11-20T06:28:48Z

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

rustbot · 2024-11-20T06:28:50Z

Some changes occurred in match checking

cc @Nadrieril

Nadrieril · 2024-11-21T18:00:35Z

I can take this

r? @Nadrieril

estebank · 2024-11-21T18:52:07Z

@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 · 2024-11-21T18:55:53Z

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

+
+/// 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>(


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 Diag directly, instead create a new Subdiagnostic type that gets added to the Diagnostic as a Vec.

Nadrieril

Phew, that was a lot. These are very helpful improvements, ty. I've raised just one correctness concern and some nits. Beyond that it's all good to me.

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

compiler/rustc_mir_build/messages.ftl

compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs

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.

…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 ```

estebank · 2024-12-04T22:05:38Z

@bors r=Nadrieril

bors · 2024-12-04T22:05:41Z

📌 Commit 4e6a401 has been approved by Nadrieril

It is now in the queue for this repository.

Add context to "const in pattern" errors *Each commit addresses specific diagnostics.* - Add primary span labels - Point at `const` item, and `const` generic param definition - Reword messages and notes - Point at generic param through which an associated `const` is being referenced - Silence const in pattern with evaluation errors when they come from `const` items that already emit a diagnostic - On non-structural type in const used as pattern, point at the type that should derive `PartialEq`

Rollup of 7 pull requests Successful merges: - rust-lang#118833 (Add lint against function pointer comparisons) - rust-lang#122161 (Fix suggestion when shorthand `self` has erroneous type) - rust-lang#133233 (Add context to "const in pattern" errors) - rust-lang#133843 (Do not emit empty suggestion) - rust-lang#133863 (Rename `core_pattern_type` and `core_pattern_types` lib feature gates to `pattern_type_macro`) - rust-lang#133872 (No need to create placeholders for GAT args in confirm_object_candidate) - rust-lang#133874 (`fn_sig_for_fn_abi` should return a `ty::FnSig`, no need for a binder) r? `@ghost` `@rustbot` modify labels: rollup

Rollup of 10 pull requests Successful merges: - rust-lang#118833 (Add lint against function pointer comparisons) - rust-lang#122161 (Fix suggestion when shorthand `self` has erroneous type) - rust-lang#133233 (Add context to "const in pattern" errors) - rust-lang#133761 (Update books) - rust-lang#133843 (Do not emit empty suggestion) - rust-lang#133863 (Rename `core_pattern_type` and `core_pattern_types` lib feature gates to `pattern_type_macro`) - rust-lang#133872 (No need to create placeholders for GAT args in confirm_object_candidate) - rust-lang#133874 (`fn_sig_for_fn_abi` should return a `ty::FnSig`, no need for a binder) - rust-lang#133890 (Add a new test ui/incoherent-inherent-impls/no-other-unrelated-errors to check E0116 does not cause unrelated errors) - rust-lang#133892 (Revert rust-lang#133817) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#133233 - estebank:const-errors, r=Nadrieril Add context to "const in pattern" errors *Each commit addresses specific diagnostics.* - Add primary span labels - Point at `const` item, and `const` generic param definition - Reword messages and notes - Point at generic param through which an associated `const` is being referenced - Silence const in pattern with evaluation errors when they come from `const` items that already emit a diagnostic - On non-structural type in const used as pattern, point at the type that should derive `PartialEq`

rustbot assigned nnethercote Nov 20, 2024

This comment has been minimized.

Sign in to view

This comment was marked as resolved.

Sign in to view

estebank force-pushed the const-errors branch from 690899a to ae7004e Compare November 20, 2024 18:38

This comment has been minimized.

Sign in to view

rustbot assigned Nadrieril and unassigned nnethercote Nov 21, 2024

estebank commented Nov 21, 2024

View reviewed changes

Nadrieril reviewed Nov 27, 2024

View reviewed changes

Nadrieril added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Nov 27, 2024

estebank added 11 commits December 4, 2024 20:29

Tweak unevaluated constant in pattern error

cc492ed

Silence errors that are implied by the errors in the `const` item definition. Add a primary span label.

Tweak ptr in pattern error

c0f0008

Conform to error style guide.

Tweak output of some const pattern errors

253eb95

- 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.

Reword message for non-structural type constant in pattern

fb2f6a4

Add context to fall-through "const pattern of non-structural type" error

27a1880

Unify wording with the regular non-structural type error.

fix test

da58406

review comments: reword messages and simplify logic

4e6a401

estebank force-pushed the const-errors branch from 11a4442 to 4e6a401 Compare December 4, 2024 20:49

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Dec 4, 2024

fmease mentioned this pull request Dec 4, 2024

Rollup of 8 pull requests #133876

Closed

fmease mentioned this pull request Dec 4, 2024

Rollup of 7 pull requests #133877

Closed

fmease mentioned this pull request Dec 5, 2024

Rollup of 10 pull requests #133893

Merged

bors merged commit 626db06 into rust-lang:master Dec 5, 2024
6 checks passed

rustbot added this to the 1.85.0 milestone Dec 5, 2024

matthiaskrgr mentioned this pull request Dec 25, 2024

ICE has escaping bound vars, so it cannot be wrapped in a dummy binder. #134764

Closed

Add context to "const in pattern" errors #133233

Add context to "const in pattern" errors #133233

Uh oh!

Conversation

estebank commented Nov 20, 2024

Uh oh!

rustbot commented Nov 20, 2024

Uh oh!

rustbot commented Nov 20, 2024

Uh oh!

This comment has been minimized.

This comment was marked as resolved.

This comment has been minimized.

Nadrieril commented Nov 21, 2024

Uh oh!

estebank commented Nov 21, 2024

Uh oh!

estebank Nov 21, 2024

Choose a reason for hiding this comment

Uh oh!

Nadrieril left a comment • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

estebank commented Dec 4, 2024

Uh oh!

bors commented Dec 4, 2024

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

6 participants

Nadrieril left a comment •

edited

Loading