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fast path for declared_generic_bounds_from_env #119084

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Merged
merged 1 commit into from
Dec 19, 2023
+12 −2
Merged

fast path for declared_generic_bounds_from_env #119084

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14 changes: 12 additions & 2 deletions compiler/rustc_infer/src/infer/outlives/verify.rs
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
use crate::infer::outlives::components::{compute_alias_components_recursive, Component};
use crate::infer::outlives::env::RegionBoundPairs;
use crate::infer::region_constraints::VerifyIfEq;
use crate::infer::VerifyBound;
use crate::infer::{GenericKind, VerifyBound};
use rustc_data_structures::sso::SsoHashSet;
use rustc_middle::ty::GenericArg;
use rustc_middle::ty::{self, OutlivesPredicate, Ty, TyCtxt};
Expand Down Expand Up @@ -245,10 +245,20 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
"declared_generic_bounds_from_env_for_erased_ty: region_bound_pair = {:?}",
(r, p)
);
// Fast path for the common case.
match (&p, erased_ty.kind()) {
// In outlive routines, all types are expected to be fully normalized.
// And therefore we can safely use structural equality for alias types.
(GenericKind::Param(p1), ty::Param(p2)) if p1 == p2 => {}
(GenericKind::Placeholder(p1), ty::Placeholder(p2)) if p1 == p2 => {}
(GenericKind::Alias(a1), ty::Alias(_, a2)) if a1.def_id == a2.def_id => {}
_ => return None,
}

let p_ty = p.to_ty(tcx);
let erased_p_ty = self.tcx.erase_regions(p_ty);
(erased_p_ty == erased_ty)
.then_some(ty::Binder::dummy(ty::OutlivesPredicate(p.to_ty(tcx), r)))
.then_some(ty::Binder::dummy(ty::OutlivesPredicate(p_ty, r)))
});

param_bounds
Expand Down