bjoernager/rust
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safely transmute<&List<Ty<'tcx>>, &List<GenericArg<'tcx>>>

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This commit is contained in:
lcnr 2022-02-07 16:05:17 +01:00
parent 45e2c2881d
commit a9c1ab82f5
3 changed files with 89 additions and 6 deletions
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22
compiler/rustc_middle/src/ty/impls_ty.rs
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@ -61,6 +61,28 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArg<'t
}
}
impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArgKind<'tcx> {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
match self {
// WARNING: We dedup cache the `HashStable` results for `List`
// while ignoring types and freely transmute
// between `List<Ty<'tcx>>` and `List<GenericArg<'tcx>>`.
// See `fn intern_type_list` for more details.
//
// We therefore hash types without adding a hash for their discriminant.
ty::subst::GenericArgKind::Type(ty) => ty.hash_stable(hcx, hasher),
ty::subst::GenericArgKind::Const(ct) => {
mem::discriminant(self).hash_stable(hcx, hasher);
ct.hash_stable(hcx, hasher);
}
ty::subst::GenericArgKind::Lifetime(lt) => {
mem::discriminant(self).hash_stable(hcx, hasher);
lt.hash_stable(hcx, hasher);
}
}
}
}
impl<'a> HashStable<StableHashingContext<'a>> for ty::RegionKind {
fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
mem::discriminant(self).hash_stable(hcx, hasher);