/// For default associated types the normalization is not possible (the value
/// from the impl could be overridden). We also can't normalize generic
/// associated types (yet) because they contain bound parameters.
+#[tracing::instrument(level = "debug", skip(tcx))]
pub fn check_type_bounds<'tcx>(
tcx: TyCtxt<'tcx>,
trait_ty: &ty::AssocItem,
// type Bar<C> =...
// }
//
- // - `impl_substs` would be `[A, B, C]`
- // - `rebased_substs` would be `[(A, B), u32, C]`, combining the substs from
- // the *trait* with the generic associated type parameters.
- let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
+ // - `impl_trait_ref` would be `<(A, B) as Foo<u32>>
+ // - `impl_ty_substs` would be `[A, B, ^0.0]`
+ // - `rebased_substs` would be `[(A, B), u32, ^0.0]`, combining the substs from
+ // the *trait* with the generic associated type parameters (as bound vars).
+ let defs: &ty::Generics = tcx.generics_of(impl_ty.def_id);
+ let mut substs = smallvec::SmallVec::with_capacity(defs.count());
+ if let Some(def_id) = defs.parent {
+ let parent_defs = tcx.generics_of(def_id);
+ InternalSubsts::fill_item(&mut substs, tcx, parent_defs, &mut |param, _| {
+ tcx.mk_param_from_def(param)
+ });
+ }
+ let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
+ smallvec::SmallVec::with_capacity(defs.count());
+ InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param.kind {
+ GenericParamDefKind::Type { .. } => {
+ let kind = ty::BoundTyKind::Param(param.name);
+ let bound_var = ty::BoundVariableKind::Ty(kind);
+ bound_vars.push(bound_var);
+ tcx.mk_ty(ty::Bound(
+ ty::INNERMOST,
+ ty::BoundTy { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
+ ))
+ .into()
+ }
+ GenericParamDefKind::Lifetime => {
+ let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
+ let bound_var = ty::BoundVariableKind::Region(kind);
+ bound_vars.push(bound_var);
+ tcx.mk_region(ty::ReLateBound(
+ ty::INNERMOST,
+ ty::BoundRegion { var: ty::BoundVar::from_usize(bound_vars.len() - 1), kind },
+ ))
+ .into()
+ }
+ GenericParamDefKind::Const { .. } => {
+ let bound_var = ty::BoundVariableKind::Const;
+ bound_vars.push(bound_var);
+ tcx.mk_const(ty::Const {
+ ty: tcx.type_of(param.def_id),
+ val: ty::ConstKind::Bound(
+ ty::INNERMOST,
+ ty::BoundVar::from_usize(bound_vars.len() - 1),
+ ),
+ })
+ .into()
+ }
+ });
+ let bound_vars = tcx.mk_bound_variable_kinds(bound_vars.into_iter());
+ let impl_ty_substs = tcx.intern_substs(&substs);
+
let rebased_substs =
impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
let impl_ty_value = tcx.type_of(impl_ty.def_id);
// impl<T> X for T where T: X { type Y = <T as X>::Y; }
}
_ => predicates.push(
- ty::Binder::dummy(ty::ProjectionPredicate {
- projection_ty: ty::ProjectionTy {
- item_def_id: trait_ty.def_id,
- substs: rebased_substs,
+ ty::Binder::bind_with_vars(
+ ty::ProjectionPredicate {
+ projection_ty: ty::ProjectionTy {
+ item_def_id: trait_ty.def_id,
+ substs: rebased_substs,
+ },
+ ty: impl_ty_value,
},
- ty: impl_ty_value,
- })
+ bound_vars,
+ )
.to_predicate(tcx),
),
};
ty::ParamEnv::new(tcx.intern_predicates(&predicates), Reveal::UserFacing)
};
+ debug!(?normalize_param_env);
+
+ let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
+ let rebased_substs =
+ impl_ty_substs.rebase_onto(tcx, impl_ty.container.id(), impl_trait_ref.substs);
tcx.infer_ctxt().enter(move |infcx| {
let constness = impl_ty
.explicit_item_bounds(trait_ty.def_id)
.iter()
.map(|&(bound, span)| {
+ debug!(?bound);
let concrete_ty_bound = bound.subst(tcx, rebased_substs);
debug!("check_type_bounds: concrete_ty_bound = {:?}", concrete_ty_bound);