Suppress self-referential associated type constraint suggestion#153921
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…nstraint-suggestion, r=estebank Suppress self-referential associated type constraint suggestion Fixes rust-lang#112104 When comparing `Option<&I::Item>` against `Option<I::Item>`, the compiler decomposes the mismatch into `expected = &<I as Iterator>::Item` vs `found = <I as Iterator>::Item`. ARM 2 in `note_and_explain_type_err` matches because `found` is a projection, and would suggest `Item = &<I as Iterator>::Item` — constraining the associated type to something that contains itself. ARM 1 (`expected_projection`) already guards against this with `found.contains(expected)`. ARM 2 was missing the symmetric check. This adds `expected.contains(found)` to the match guard. Before: ```rust help: consider constraining the associated type `<I as Iterator>::Item` to `&<I as Iterator>::Item` | 1 | fn foo<I: Iterator<Item = &<I as Iterator>::Item>>(iter: &mut I) { | +++++++++++++++++++++++++++++++ ``` After: bogus suggestion is gone, and the existing `.as_ref()` suggestion from `hir_typeck` still fires correctly. r? @estebank
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Rollup of 5 pull requests Successful merges: - #146013 (Add `From` impls for wrapper types) - #153966 (suggest valid features when target feature is invalid) - #153372 (Fix LegacyKeyValueFormat report from docker build: x86_64-gnu) - #153738 (Don't look for non-type-level assoc consts when checking trait object types) - #153921 (Suppress self-referential associated type constraint suggestion)
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…nstraint-suggestion, r=estebank Suppress self-referential associated type constraint suggestion Fixes rust-lang#112104 When comparing `Option<&I::Item>` against `Option<I::Item>`, the compiler decomposes the mismatch into `expected = &<I as Iterator>::Item` vs `found = <I as Iterator>::Item`. ARM 2 in `note_and_explain_type_err` matches because `found` is a projection, and would suggest `Item = &<I as Iterator>::Item` — constraining the associated type to something that contains itself. ARM 1 (`expected_projection`) already guards against this with `found.contains(expected)`. ARM 2 was missing the symmetric check. This adds `expected.contains(found)` to the match guard. Before: ```rust help: consider constraining the associated type `<I as Iterator>::Item` to `&<I as Iterator>::Item` | 1 | fn foo<I: Iterator<Item = &<I as Iterator>::Item>>(iter: &mut I) { | +++++++++++++++++++++++++++++++ ``` After: bogus suggestion is gone, and the existing `.as_ref()` suggestion from `hir_typeck` still fires correctly. r? @estebank
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Rollup of 5 pull requests Successful merges: - #153966 (suggest valid features when target feature is invalid) - #153372 (Fix LegacyKeyValueFormat report from docker build: x86_64-gnu) - #153738 (Don't look for non-type-level assoc consts when checking trait object types) - #153907 (Remove redundant fields from `QueryStackFrame`) - #153921 (Suppress self-referential associated type constraint suggestion)
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Fixes #112104
When comparing
Option<&I::Item>againstOption<I::Item>, the compiler decomposes the mismatch intoexpected = &<I as Iterator>::Itemvsfound = <I as Iterator>::Item. ARM 2 innote_and_explain_type_errmatches becausefoundis a projection, and would suggestItem = &<I as Iterator>::Item— constraining the associated type to something that contains itself.ARM 1 (
expected_projection) already guards against this withfound.contains(expected). ARM 2 was missing the symmetric check. This addsexpected.contains(found)to the match guard.Before:
After: bogus suggestion is gone, and the existing
.as_ref()suggestion fromhir_typeckstill fires correctly.r? @estebank