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Actually just remove the special case altogether
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@compiler-errors
compiler-errors committed May 24, 2024
1 parent a94beac commit 0c46d8c
Showing 1 changed file with 47 additions and 76 deletions.
123 changes: 47 additions & 76 deletions compiler/rustc_hir_analysis/src/collect/predicates_of.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -461,84 +461,55 @@ pub(super) fn explicit_predicates_of<'tcx>(
}
}
} else {
if matches!(def_kind, DefKind::AnonConst) && tcx.features().generic_const_exprs {
let hir_id = tcx.local_def_id_to_hir_id(def_id);
// FIXME(generic_const_exprs): The parenting of this def id is sketchy.
// That should be fixed.
let parent_def_id = tcx.hir().get_parent_item(hir_id);

if let Some(defaulted_param_def_id) =
tcx.hir().opt_const_param_default_param_def_id(hir_id)
{
// In `generics_of` we set the generics' parent to be our parent's parent which means that
// we lose out on the predicates of our actual parent if we dont return those predicates here.
// (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
//
// struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
// ^^^ ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
// ^^^ explicit_predicates_of on
// parent item we dont have set as the
// parent of generics returned by `generics_of`
//
// In the above code we want the anon const to have predicates in its param env for `T: Trait`
// and we would be calling `explicit_predicates_of(Foo)` here
let parent_preds = tcx.explicit_predicates_of(parent_def_id);

// If we dont filter out `ConstArgHasType` predicates then every single defaulted const parameter
// will ICE because of #106994. FIXME(generic_const_exprs): remove this when a more general solution
// to #106994 is implemented.
let filtered_predicates = parent_preds
.predicates
.into_iter()
.filter(|(pred, _)| {
if let ty::ClauseKind::ConstArgHasType(ct, _) = pred.kind().skip_binder() {
match ct.kind() {
ty::ConstKind::Param(param_const) => {
let defaulted_param_idx = tcx
.generics_of(parent_def_id)
.param_def_id_to_index[&defaulted_param_def_id.to_def_id()];
param_const.index < defaulted_param_idx
}
_ => bug!(
"`ConstArgHasType` in `predicates_of`\
that isn't a `Param` const"
),
if matches!(def_kind, DefKind::AnonConst)
&& tcx.features().generic_const_exprs
&& let Some(defaulted_param_def_id) =
tcx.hir().opt_const_param_default_param_def_id(tcx.local_def_id_to_hir_id(def_id))
{
// In `generics_of` we set the generics' parent to be our parent's parent which means that
// we lose out on the predicates of our actual parent if we dont return those predicates here.
// (See comment in `generics_of` for more information on why the parent shenanigans is necessary)
//
// struct Foo<T, const N: usize = { <T as Trait>::ASSOC }>(T) where T: Trait;
// ^^^ ^^^^^^^^^^^^^^^^^^^^^^^ the def id we are calling
// ^^^ explicit_predicates_of on
// parent item we dont have set as the
// parent of generics returned by `generics_of`
//
// In the above code we want the anon const to have predicates in its param env for `T: Trait`
// and we would be calling `explicit_predicates_of(Foo)` here
let parent_def_id = tcx.local_parent(def_id);
let parent_preds = tcx.explicit_predicates_of(parent_def_id);

// If we dont filter out `ConstArgHasType` predicates then every single defaulted const parameter
// will ICE because of #106994. FIXME(generic_const_exprs): remove this when a more general solution
// to #106994 is implemented.
let filtered_predicates = parent_preds
.predicates
.into_iter()
.filter(|(pred, _)| {
if let ty::ClauseKind::ConstArgHasType(ct, _) = pred.kind().skip_binder() {
match ct.kind() {
ty::ConstKind::Param(param_const) => {
let defaulted_param_idx = tcx
.generics_of(parent_def_id)
.param_def_id_to_index[&defaulted_param_def_id.to_def_id()];
param_const.index < defaulted_param_idx
}
} else {
true
_ => bug!(
"`ConstArgHasType` in `predicates_of`\
that isn't a `Param` const"
),
}
})
.cloned();
return GenericPredicates {
parent: parent_preds.parent,
predicates: { tcx.arena.alloc_from_iter(filtered_predicates) },
};
}

let parent_def_kind = tcx.def_kind(parent_def_id);
if matches!(parent_def_kind, DefKind::OpaqueTy) {
// In `instantiate_identity` we inherit the predicates of our parent.
// However, opaque types do not have a parent (see `gather_explicit_predicates_of`), which means
// that we lose out on the predicates of our actual parent if we dont return those predicates here.
//
//
// fn foo<T: Trait>() -> impl Iterator<Output = Another<{ <T as Trait>::ASSOC }> > { todo!() }
// ^^^^^^^^^^^^^^^^^^^ the def id we are calling
// explicit_predicates_of on
//
// In the above code we want the anon const to have predicates in its param env for `T: Trait`.
// However, the anon const cannot inherit predicates from its parent since it's opaque.
//
// To fix this, we call `explicit_predicates_of` directly on `foo`, the parent's parent.

let (hir::OpaqueTyOrigin::FnReturn(item_owner_def_id)
| hir::OpaqueTyOrigin::AsyncFn(item_owner_def_id)
| hir::OpaqueTyOrigin::TyAlias { parent: item_owner_def_id, .. }) =
tcx.opaque_type_origin(parent_def_id.def_id);

// In the above code example we would be calling `explicit_predicates_of(foo)` here
return tcx.explicit_predicates_of(item_owner_def_id);
}
} else {
true
}
})
.cloned();
return GenericPredicates {
parent: parent_preds.parent,
predicates: { tcx.arena.alloc_from_iter(filtered_predicates) },
};
}
gather_explicit_predicates_of(tcx, def_id)
}
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