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

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Jul 8, 2023
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Remove variances_of on RPITIT GATs, remove its one use-case #113427

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12 changes: 3 additions & 9 deletions compiler/rustc_hir_analysis/src/variance/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use rustc_arena::DroplessArena;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::{DefId, LocalDefId};
use rustc_middle::query::Providers;
use rustc_middle::ty::{self, CrateVariancesMap, ImplTraitInTraitData, SubstsRef, Ty, TyCtxt};
use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
use std::ops::ControlFlow;

Expand Down Expand Up @@ -59,13 +59,6 @@ fn variances_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Variance] {
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.

if let Some(ImplTraitInTraitData::Trait { .. }) =
tcx.opt_rpitit_info(item_def_id.to_def_id())
{
return variance_of_opaque(tcx, item_def_id);
}
}
_ => {}
}

Expand Down Expand Up @@ -125,7 +118,8 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
// FIXME(-Zlower-impl-trait-in-trait-to-assoc-ty) check whether this is necessary
// at all for RPITITs.
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.

{
self.visit_opaque(*def_id, substs)
}
Expand Down
11 changes: 0 additions & 11 deletions compiler/rustc_infer/src/infer/opaque_types.rs
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Expand Up @@ -473,17 +473,6 @@ where
}
}

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.

// Skip lifetime parameters that are not captures.
let variances = self.tcx.variances_of(proj.def_id);

for (v, s) in std::iter::zip(variances, proj.substs.iter()) {
if *v != ty::Variance::Bivariant {
s.visit_with(self);
}
}
}

_ => {
ty.super_visit_with(self);
}
Expand Down
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