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Erase regions when confirming transmutability candidate

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This commit is contained in:
Michael Goulet
2023-04-07 05:25:56 +00:00
parent 8a778ca1e3
commit f6bfb4bf8e
8 changed files with 88 additions and 44 deletions
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46
compiler/rustc_trait_selection/src/traits/select/confirmation.rs
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@@ -275,33 +275,35 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) -> Result<ImplSourceBuiltinData<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
debug!(?obligation, "confirm_transmutability_candidate");
let predicate = obligation.predicate;
// We erase regions here because transmutability calls layout queries,
// which does not handle inference regions and doesn't particularly
// care about other regions. Erasing late-bound regions is equivalent
// to instantiating the binder with placeholders then erasing those
// placeholder regions.
let predicate =
self.tcx().erase_regions(self.tcx().erase_late_bound_regions(obligation.predicate));
let type_at = |i| predicate.map_bound(|p| p.trait_ref.substs.type_at(i));
let const_at = |i| predicate.skip_binder().trait_ref.substs.const_at(i);
let src_and_dst = predicate.map_bound(|p| rustc_transmute::Types {
dst: p.trait_ref.substs.type_at(0),
src: p.trait_ref.substs.type_at(1),
});
let scope = type_at(2).skip_binder();
let Some(assume) =
rustc_transmute::Assume::from_const(self.infcx.tcx, obligation.param_env, const_at(3)) else {
return Err(Unimplemented);
};
let cause = obligation.cause.clone();
let Some(assume) = rustc_transmute::Assume::from_const(
self.infcx.tcx,
obligation.param_env,
predicate.trait_ref.substs.const_at(3)
) else {
return Err(Unimplemented);
};
let mut transmute_env = rustc_transmute::TransmuteTypeEnv::new(self.infcx);
let maybe_transmutable = transmute_env.is_transmutable(cause, src_and_dst, scope, assume);
use rustc_transmute::Answer;
let maybe_transmutable = transmute_env.is_transmutable(
obligation.cause.clone(),
rustc_transmute::Types {
dst: predicate.trait_ref.substs.type_at(0),
src: predicate.trait_ref.substs.type_at(1),
},
predicate.trait_ref.substs.type_at(2),
assume,
);
match maybe_transmutable {
Answer::Yes => Ok(ImplSourceBuiltinData { nested: vec![] }),
rustc_transmute::Answer::Yes => Ok(ImplSourceBuiltinData { nested: vec![] }),
_ => Err(Unimplemented),
}
}