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Remove variances_of on RPITIT GATs, remove its one use-case#113427

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compiler-errors:no-variances-of-rpitit-gat
Jul 8, 2023
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Remove variances_of on RPITIT GATs, remove its one use-case#113427
bors merged 1 commit intorust-lang:masterfrom
compiler-errors:no-variances-of-rpitit-gat

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@compiler-errors compiler-errors commented Jul 7, 2023

It doesn't make sense to implement variances on a GAT anyways, since we don't relate GATs with variance:

rust/compiler/rustc_middle/src/ty/relate.rs

Lines 569 to 579 in 85bf079

(&ty::Alias(a_kind, a_data), &ty::Alias(b_kind, b_data)) => {
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty): This if can be removed
// and the assert uncommented once the new desugaring is stable.
if a_kind == b_kind {
let alias_ty = relation.relate(a_data, b_data)?;
// assert_eq!(a_kind, b_kind);
Ok(Ty::new_alias(tcx, a_kind, alias_ty))
} else {
Err(TypeError::Sorts(expected_found(relation, a, b)))
}
}

r? @spastorino

@rustbot 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 Jul 7, 2023
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compiler-errors commented Jul 7, 2023
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Comment thread compiler/rustc_hir_analysis/src/variance/mod.rs
DefKind::OpaqueTy | DefKind::ImplTraitPlaceholder => {
return variance_of_opaque(tcx, item_def_id);
}
DefKind::AssocTy => {
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This is unreachable given the deleted code below.

Comment thread compiler/rustc_hir_analysis/src/variance/mod.rs
ty::Alias(_, ty::AliasTy { def_id, substs, .. })
if self.tcx.is_impl_trait_in_trait(*def_id) =>
if self.tcx.is_impl_trait_in_trait(*def_id)
&& !self.tcx.lower_impl_trait_in_trait_to_assoc_ty() =>
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In the new lowering scheme, we should never need to consider the variances on a RPITIT GAT.

Comment thread compiler/rustc_infer/src/infer/opaque_types.rs
}
}

ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => {
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In the new lowering scheme, we should never need to consider the variances of a RPITIT GAT.

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spastorino commented Jul 7, 2023 •
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r=me with CI green

@bors rollup

@compiler-errors compiler-errors changed the title Remove variances_of on RPITIT gats, remove its one use-case Remove variances_of on RPITIT GATs, remove its one use-case Jul 7, 2023
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compiler-errors commented Jul 7, 2023

@bors r=spastorino

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bors commented Jul 7, 2023

📌 Commit ca8202d has been approved by spastorino

It is now in the queue for this repository.

@bors 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-review Status: Awaiting review from the assignee but also interested parties. labels Jul 7, 2023
@spastorino spastorino mentioned this pull request Jul 7, 2023
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GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Jul 7, 2023
@GuillaumeGomez
Rollup merge of rust-lang#113427 - compiler-errors:no-variances-of-rp…
ba711ba 
…itit-gat, r=spastorino

Remove `variances_of` on RPITIT GATs, remove its one use-case

It doesn't make sense to implement variances on a GAT anyways, since we don't relate GATs with variance:

https://github.com/rust-lang/rust/blob/85bf07972a1041b9e25393b803d0e006bec3eaaf/compiler/rustc_middle/src/ty/relate.rs#L569-L579

r? `@spastorino`
@GuillaumeGomez GuillaumeGomez mentioned this pull request Jul 7, 2023
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compiler-errors commented Jul 7, 2023

@bors rollup

GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Jul 7, 2023
@GuillaumeGomez
Rollup merge of rust-lang#113427 - compiler-errors:no-variances-of-rp…
d8de054 
…itit-gat, r=spastorino

Remove `variances_of` on RPITIT GATs, remove its one use-case

It doesn't make sense to implement variances on a GAT anyways, since we don't relate GATs with variance:

https://github.com/rust-lang/rust/blob/85bf07972a1041b9e25393b803d0e006bec3eaaf/compiler/rustc_middle/src/ty/relate.rs#L569-L579

r? `@spastorino`
@GuillaumeGomez GuillaumeGomez mentioned this pull request Jul 7, 2023
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@compiler-errors compiler-errors mentioned this pull request Jul 8, 2023
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jul 8, 2023
@bors
Auto merge of rust-lang#113474 - compiler-errors:rollup-07x1up7, r=co…
ce519c5 
…mpiler-errors

Rollup of 8 pull requests

Successful merges:

 - rust-lang#113413 (Add needs-triage to all new issues)
 - rust-lang#113426 (Don't ICE in `resolve_bound_vars` when associated return-type bounds are in bad positions)
 - rust-lang#113427 (Remove `variances_of` on RPITIT GATs, remove its one use-case)
 - rust-lang#113441 (miri: check that assignments do not self-overlap)
 - rust-lang#113453 (Remove unused from_method from rustc_on_unimplemented)
 - rust-lang#113456 (Avoid calling report_forbidden_specialization for RPITITs)
 - rust-lang#113466 (Update cargo)
 - rust-lang#113467 (Fix comment of `fn_can_unwind`)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 751dcac into rust-lang:master Jul 8, 2023
@rustbot rustbot added this to the 1.72.0 milestone Jul 8, 2023
@compiler-errors compiler-errors deleted the no-variances-of-rpitit-gat branch August 11, 2023 20:11
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