For a single impl candidate, try to unify it with error trait ref #115726

compiler-errors · 2023-09-10T03:38:37Z

This allows us to point out an exact type mismatch when there's only one applicable impl.

compiler-errors · 2023-09-10T03:39:07Z

tests/ui/const-generics/occurs-check/unused-substs-1.stderr

@@ -4,7 +4,7 @@ error[E0277]: the trait bound `A<_>: Bar<_>` is not satisfied
 LL |     let _ = A;
   |             ^ the trait `Bar<_>` is not implemented for `A<_>`
   |
-   = help: the trait `Bar<N>` is implemented for `A<7>`
+   = help: the trait `Bar<_>` is implemented for `A<7>`


This isn't better but it's also not worse 💀

While this case isn't that much worse, there are cases where it shows something like UwU<_> is implemented for OwO<_> which no longer indicates that the type that's being printed as _ is the same in both cases. (I dislike that that sort of printing for types is ever done, but that's not specific to this PR.)

Yeah, I wonder if we could plug up the remaining infer vars here, so that those two Owo<_> and Uwu<_> are re-connected with some placeholder name.

compiler-errors · 2023-09-10T03:41:19Z

tests/ui/generic-const-items/unsatisfied-bounds.stderr

@@ -17,6 +17,7 @@ LL |     let () = K::<()>;
   |                  ^^ the trait `From<()>` is not implemented for `Infallible`
   |
   = help: the trait `From<!>` is implemented for `Infallible`
+   = help: ... for that trait implementation, expected `!`, found `()`


Not exactly sure what the best presentation for this is 🤔

estebank · 2023-09-27T01:43:51Z

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

+                if let [TypeError::Sorts(exp_found)] = &terrs[..] {
+                    let exp_found = self.resolve_vars_if_possible(*exp_found);
+                    err.help(format!(
+                        "... for that trait implementation, expected `{}`, found `{}`",


Suggested change

"... for that trait implementation, expected `{}`, found `{}`",

"for that trait implementation, expected `{}`, found `{}`",

compiler-errors · 2023-09-27T01:46:14Z

@rustbot author

estebank · 2023-09-27T01:46:15Z

r=me after addressing the nitpick

compiler-errors · 2023-10-02T23:46:57Z

@bors r=estebank

bors · 2023-10-02T23:46:59Z

📌 Commit 0785167 has been approved by estebank

It is now in the queue for this repository.

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#113053 (add notes about non-compliant FP behavior on 32bit x86 targets) - rust-lang#115726 (For a single impl candidate, try to unify it with error trait ref) - rust-lang#116158 (Don't suggest nonsense suggestions for unconstrained type vars in `note_source_of_type_mismatch_constraint`) - rust-lang#116351 (Add `must_use` on pointer equality functions) - rust-lang#116355 (Clarify float rounding direction for signed zero) - rust-lang#116361 (Bump stdarch submodule) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of rust-lang#115726 - compiler-errors:better-error-ref, r=estebank For a single impl candidate, try to unify it with error trait ref This allows us to point out an exact type mismatch when there's only one applicable impl. cc `@asquared31415` r? `@estebank`

rustbot assigned estebank Sep 10, 2023

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 Sep 10, 2023

compiler-errors commented Sep 10, 2023

View reviewed changes

estebank reviewed Sep 27, 2023

View reviewed changes

rustbot 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 Sep 27, 2023

compiler-errors added 2 commits October 2, 2023 23:14

For a single impl candidate, try to unify it with error trait ref

8be12f4

Point out the actual mismatch error

0785167

rust-cloud-vms bot force-pushed the better-error-ref branch from 3c81efe to 0785167 Compare October 2, 2023 23:14

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 Oct 2, 2023

matthiaskrgr mentioned this pull request Oct 3, 2023

Rollup of 6 pull requests #116372

Merged

bors merged commit ff3b15e into rust-lang:master Oct 3, 2023
11 checks passed

rustbot added this to the 1.75.0 milestone Oct 3, 2023

pvdrz mentioned this pull request Oct 4, 2023

Fix divergence from upstream master ferrocene/ferrocene#23

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For a single impl candidate, try to unify it with error trait ref #115726

For a single impl candidate, try to unify it with error trait ref #115726

compiler-errors commented Sep 10, 2023

compiler-errors Sep 10, 2023

asquared31415 Sep 11, 2023

compiler-errors Sep 27, 2023

compiler-errors Sep 10, 2023

estebank Sep 27, 2023 •

edited

compiler-errors commented Sep 27, 2023

estebank commented Sep 27, 2023

compiler-errors commented Oct 2, 2023

bors commented Oct 2, 2023

	"... for that trait implementation, expected `{}`, found `{}`",
	"for that trait implementation, expected `{}`, found `{}`",

For a single impl candidate, try to unify it with error trait ref #115726

For a single impl candidate, try to unify it with error trait ref #115726

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compiler-errors commented Sep 10, 2023

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estebank Sep 27, 2023 • edited

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compiler-errors commented Sep 27, 2023

estebank commented Sep 27, 2023

compiler-errors commented Oct 2, 2023

bors commented Oct 2, 2023

estebank Sep 27, 2023 •

edited