Make generic const type mismatches not hide trait impls from the trait solver #120059

oli-obk · 2024-01-17T14:59:44Z

pulled out of #119895

It does improve diagnostics somewhat, but also causes some extraneous diagnostics in potentially misleading order.

The issue was that a const type mismatch, instead of reporting an error, would silently poison the constant, only for that information to be thrown away and the impl to be treated as "not matching". In #119895 this would cause ICEs as well as errors on impls stating that the impl needs to exist for itself to be valid.

rustbot · 2024-01-17T14:59:53Z

r? @wesleywiser

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compiler-errors · 2024-01-17T19:27:08Z

Why aren't you happy with this change? It doesn't seem to make diagnostics much worse -- the only material change is that we flip a type error into a coherence overlap error, but both of them are valid errors, so the choice seems a bit arbitrary.

I'm happy to approve this if you want to actually give it a real description and title and stuff. Otherwise, I'd like to hear more about your reservations with this change.

oli-obk · 2024-01-18T09:00:47Z

tests/ui/const-generics/bad-subst-const-kind.stderr

+error: the constant `13` is not of type `u64`
+  --> $DIR/bad-subst-const-kind.rs:13:24
+   |
+LL | pub fn test() -> [u8; <[u8; 13] as Q>::ASSOC] { todo!() }
+   |                        ^^^^^^^^ expected `u64`, found `usize`


the compiler suggests using a u64 as an array length

yeah we have bad spans for this in general

oli-obk · 2024-01-18T09:02:16Z

tests/ui/const-generics/bad-subst-const-kind.stderr

 error[E0308]: mismatched types
  --> $DIR/bad-subst-const-kind.rs:8:31
   |
 LL | impl<const N: u64> Q for [u8; N] {
   |                               ^ expected `usize`, found `u64`



This is the only diagnostic I would expect to see. But I haven't figured out yet how to poison the impl so it doesn't get picked up

oli-obk · 2024-01-18T09:02:56Z

tests/ui/const-generics/generic_const_exprs/type_mismatch.stderr

+error[E0308]: mismatched types
+  --> $DIR/type_mismatch.rs:8:31
+   |
+LL | impl<const N: u64> Q for [u8; N] {}
+   |                               ^ expected `usize`, found `u64`
+


This is good, I want this error. But now we also got a bunch of "follow-up" errors happening before. Maybe we can move whatever causes this error into a query that is guaranteed to be called before impl overlap checking

tests/ui/specialization/min_specialization/bad-const-wf-doesnt-specialize.rs

rustbot · 2024-01-18T09:05:38Z

Type relation code was changed

cc @compiler-errors, @lcnr

compiler/rustc_infer/src/infer/relate/combine.rs

compiler-errors

I'm ok w the state of these errors right now.

r=me unless you want to continue to iterate on this, though I guess you could/should probably file a follow-up diagnostic issue for the really bad case of tests/ui/const-generics/bad-subst-const-kind.rs since I agree that one is particularly confusing.

oli-obk · 2024-01-18T22:14:51Z

@bors r=compiler-errors

I have tried a few things, but it's very hard to improve the span here. All we have is the span of the array, and it's a ty::Array with an already evaluated length const.

I'll keep digging

bors · 2024-01-18T22:14:54Z

📌 Commit 2040c1c has been approved by compiler-errors

It is now in the queue for this repository.

…=compiler-errors Make generic const type mismatches not hide trait impls from the trait solver pulled out of rust-lang#119895 It does improve diagnostics somewhat, but also causes some extraneous diagnostics in potentially misleading order. The issue was that a const type mismatch, instead of reporting an error, would silently poison the constant, only for that information to be thrown away and the impl to be treated as "not matching". In rust-lang#119895 this would cause ICEs as well as errors on impls stating that the impl needs to exist for itself to be valid.

compiler-errors · 2024-01-20T19:40:49Z

@bors r-

#120162 (comment)

…t solver

oli-obk · 2024-01-22T13:25:13Z

@bors r=compiler-errors

after a rebase over #119869 the missing diagnostic is back 🎉

bors · 2024-01-22T13:25:15Z

📌 Commit 9454b51 has been approved by compiler-errors

It is now in the queue for this repository.

…=compiler-errors Make generic const type mismatches not hide trait impls from the trait solver pulled out of rust-lang#119895 It does improve diagnostics somewhat, but also causes some extraneous diagnostics in potentially misleading order. The issue was that a const type mismatch, instead of reporting an error, would silently poison the constant, only for that information to be thrown away and the impl to be treated as "not matching". In rust-lang#119895 this would cause ICEs as well as errors on impls stating that the impl needs to exist for itself to be valid.

…iaskrgr Rollup of 11 pull requests Successful merges: - rust-lang#117910 (Refactor uses of `objc_msgSend` to no longer have clashing definitions) - rust-lang#118639 (Undeprecate lint `unstable_features` and make use of it in the compiler) - rust-lang#119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in) - rust-lang#120058 (bootstrap: improvements for compiler builds) - rust-lang#120059 (Make generic const type mismatches not hide trait impls from the trait solver) - rust-lang#120097 (Report unreachable subpatterns consistently) - rust-lang#120137 (Validate AggregateKind types in MIR) - rust-lang#120164 (`maybe_lint_impl_trait`: separate `is_downgradable` from `is_object_safe`) - rust-lang#120181 (Allow any `const` expression blocks in `thread_local!`) - rust-lang#120204 (Builtin macros effectively have implicit #[collapse_debuginfo(yes)]) - rust-lang#120218 (rustfmt: Check that a token can begin a nonterminal kind before parsing it as a macro arg) r? `@ghost` `@rustbot` modify labels: rollup

…iaskrgr Rollup of 10 pull requests Successful merges: - rust-lang#117910 (Refactor uses of `objc_msgSend` to no longer have clashing definitions) - rust-lang#118639 (Undeprecate lint `unstable_features` and make use of it in the compiler) - rust-lang#119801 (Fix deallocation with wrong allocator in (A)Rc::from_box_in) - rust-lang#120058 (bootstrap: improvements for compiler builds) - rust-lang#120059 (Make generic const type mismatches not hide trait impls from the trait solver) - rust-lang#120097 (Report unreachable subpatterns consistently) - rust-lang#120137 (Validate AggregateKind types in MIR) - rust-lang#120164 (`maybe_lint_impl_trait`: separate `is_downgradable` from `is_object_safe`) - rust-lang#120181 (Allow any `const` expression blocks in `thread_local!`) - rust-lang#120218 (rustfmt: Check that a token can begin a nonterminal kind before parsing it as a macro arg) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#120059 - oli-obk:const_arg_type_mismatch, r=compiler-errors Make generic const type mismatches not hide trait impls from the trait solver pulled out of rust-lang#119895 It does improve diagnostics somewhat, but also causes some extraneous diagnostics in potentially misleading order. The issue was that a const type mismatch, instead of reporting an error, would silently poison the constant, only for that information to be thrown away and the impl to be treated as "not matching". In rust-lang#119895 this would cause ICEs as well as errors on impls stating that the impl needs to exist for itself to be valid.

rustbot assigned wesleywiser Jan 17, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jan 17, 2024

oli-obk mentioned this pull request Jan 17, 2024

Remove track_errors entirely #119895

Merged

compiler-errors assigned compiler-errors and unassigned wesleywiser Jan 17, 2024

oli-obk commented Jan 18, 2024

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oli-obk changed the title ~~WIP: Experimental extraction of a change from a larger PR~~ Make generic const type mismatches not hide trait impls from the trait solver Jan 18, 2024

oli-obk marked this pull request as ready for review January 18, 2024 09:05

lcnr reviewed Jan 18, 2024

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compiler/rustc_infer/src/infer/relate/combine.rs Outdated Show resolved Hide resolved

oli-obk force-pushed the const_arg_type_mismatch branch from 9265e13 to 2040c1c Compare January 18, 2024 09:54

compiler-errors approved these changes Jan 18, 2024

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compiler-errors 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 Jan 18, 2024

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 Jan 18, 2024

GuillaumeGomez mentioned this pull request Jan 20, 2024

Rollup of 8 pull requests #120162

Closed

bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jan 20, 2024

Make generic const type mismatches not hide trait impls from the trai…

9454b51

…t solver

oli-obk force-pushed the const_arg_type_mismatch branch from 2040c1c to 9454b51 Compare January 22, 2024 13:23

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 Jan 22, 2024

matthiaskrgr mentioned this pull request Jan 22, 2024

Rollup of 11 pull requests #120237

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matthiaskrgr mentioned this pull request Jan 22, 2024

Rollup of 10 pull requests #120242

Merged

bors merged commit d942357 into rust-lang:master Jan 22, 2024
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rustbot added this to the 1.77.0 milestone Jan 22, 2024

oli-obk deleted the const_arg_type_mismatch branch January 23, 2024 11:12

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Make generic const type mismatches not hide trait impls from the trait solver #120059

Make generic const type mismatches not hide trait impls from the trait solver #120059

oli-obk commented Jan 17, 2024 •

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Make generic const type mismatches not hide trait impls from the trait solver #120059

Make generic const type mismatches not hide trait impls from the trait solver #120059

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