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Check generic argument compatibility when projecting assoc ty

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This commit is contained in:
Michael Goulet 2022-09-29 21:22:34 +00:00
parent 594134d873
commit ee713f3d43
3 changed files with 68 additions and 2 deletions
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42
compiler/rustc_trait_selection/src/traits/project.rs
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@ -2146,10 +2146,10 @@ fn confirm_impl_candidate<'cx, 'tcx>(
} else {
ty.map_bound(|ty| ty.into())
};
if substs.len() != tcx.generics_of(assoc_ty.item.def_id).count() {
if !check_substs_compatible(tcx, &assoc_ty.item, substs) {
let err = tcx.ty_error_with_message(
obligation.cause.span,
"impl item and trait item have different parameter counts",
"impl item and trait item have different parameters",
);
Progress { term: err.into(), obligations: nested }
} else {
@ -2158,6 +2158,44 @@ fn confirm_impl_candidate<'cx, 'tcx>(
}
}
// Verify that the trait item and its implementation have compatible substs lists
fn check_substs_compatible<'tcx>(
tcx: TyCtxt<'tcx>,
assoc_ty: &ty::AssocItem,
substs: ty::SubstsRef<'tcx>,
) -> bool {
fn check_substs_compatible_inner<'tcx>(
tcx: TyCtxt<'tcx>,
generics: &'tcx ty::Generics,
args: &'tcx [ty::GenericArg<'tcx>],
) -> bool {
if generics.count() != args.len() {
return false;
}
let (parent_args, own_args) = args.split_at(generics.parent_count);
if let Some(parent) = generics.parent
&& let parent_generics = tcx.generics_of(parent)
&& !check_substs_compatible_inner(tcx, parent_generics, parent_args) {
return false;
}
for (param, arg) in std::iter::zip(&generics.params, own_args) {
match (&param.kind, arg.unpack()) {
(ty::GenericParamDefKind::Type { .. }, ty::GenericArgKind::Type(_))
| (ty::GenericParamDefKind::Lifetime, ty::GenericArgKind::Lifetime(_))
| (ty::GenericParamDefKind::Const { .. }, ty::GenericArgKind::Const(_)) => {}
_ => return false,
}
}
true
}
check_substs_compatible_inner(tcx, tcx.generics_of(assoc_ty.def_id), substs.as_slice())
}
fn confirm_impl_trait_in_trait_candidate<'tcx>(
selcx: &mut SelectionContext<'_, 'tcx>,
obligation: &ProjectionTyObligation<'tcx>,