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More compare_impl_item simplifications
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@compiler-errors
compiler-errors committed Oct 20, 2024
1 parent 73a37a1 commit 7daa9f2
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Showing 3 changed files with 73 additions and 37 deletions.
64 changes: 30 additions & 34 deletions compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -167,8 +167,6 @@ fn compare_method_predicate_entailment<'tcx>(
trait_m: ty::AssocItem,
impl_trait_ref: ty::TraitRef<'tcx>,
) -> Result<(), ErrorGuaranteed> {
let trait_to_impl_args = impl_trait_ref.args;

// This node-id should be used for the `body_id` field on each
// `ObligationCause` (and the `FnCtxt`).
//
Expand All @@ -183,13 +181,13 @@ fn compare_method_predicate_entailment<'tcx>(
kind: impl_m.kind,
});

// Create mapping from impl to placeholder.
let impl_to_placeholder_args = GenericArgs::identity_for_item(tcx, impl_m.def_id);

// Create mapping from trait to placeholder.
let trait_to_placeholder_args =
impl_to_placeholder_args.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_args);
debug!("compare_impl_method: trait_to_placeholder_args={:?}", trait_to_placeholder_args);
let trait_to_impl_args = GenericArgs::identity_for_item(tcx, impl_m.def_id).rebase_onto(
tcx,
impl_m.container_id(tcx),
impl_trait_ref.args,
);
debug!("compare_impl_method: trait_to_placeholder_args={:?}", trait_to_impl_args);

let impl_m_predicates = tcx.predicates_of(impl_m.def_id);
let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
Expand All @@ -204,9 +202,7 @@ fn compare_method_predicate_entailment<'tcx>(
let impl_predicates = tcx.predicates_of(impl_m_predicates.parent.unwrap());
let mut hybrid_preds = impl_predicates.instantiate_identity(tcx).predicates;
hybrid_preds.extend(
trait_m_predicates
.instantiate_own(tcx, trait_to_placeholder_args)
.map(|(predicate, _)| predicate),
trait_m_predicates.instantiate_own(tcx, trait_to_impl_args).map(|(predicate, _)| predicate),
);

// Construct trait parameter environment and then shift it into the placeholder viewpoint.
Expand All @@ -225,7 +221,7 @@ fn compare_method_predicate_entailment<'tcx>(
// definition in the context of the hybrid param-env. This makes
// sure that the impl's method's where clauses are not more
// restrictive than the trait's method (and the impl itself).
let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_args);
let impl_m_own_bounds = impl_m_predicates.instantiate_own_identity();
for (predicate, span) in impl_m_own_bounds {
let normalize_cause = traits::ObligationCause::misc(span, impl_m_def_id);
let predicate = ocx.normalize(&normalize_cause, param_env, predicate);
Expand All @@ -252,7 +248,6 @@ fn compare_method_predicate_entailment<'tcx>(
// any associated types appearing in the fn arguments or return
// type.

// Compute placeholder form of impl and trait method tys.
let mut wf_tys = FxIndexSet::default();

let unnormalized_impl_sig = infcx.instantiate_binder_with_fresh_vars(
Expand All @@ -265,7 +260,7 @@ fn compare_method_predicate_entailment<'tcx>(
let impl_sig = ocx.normalize(&norm_cause, param_env, unnormalized_impl_sig);
debug!("compare_impl_method: impl_fty={:?}", impl_sig);

let trait_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_placeholder_args);
let trait_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_impl_args);
let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, trait_sig);

// Next, add all inputs and output as well-formed tys. Importantly,
Expand Down Expand Up @@ -451,8 +446,6 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
// just so we don't ICE during instantiation later.
check_method_is_structurally_compatible(tcx, impl_m, trait_m, impl_trait_ref, true)?;

let trait_to_impl_args = impl_trait_ref.args;

let impl_m_hir_id = tcx.local_def_id_to_hir_id(impl_m_def_id);
let return_span = tcx.hir().fn_decl_by_hir_id(impl_m_hir_id).unwrap().output.span();
let cause =
Expand All @@ -462,18 +455,18 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
kind: impl_m.kind,
});

// Create mapping from impl to placeholder.
let impl_to_placeholder_args = GenericArgs::identity_for_item(tcx, impl_m.def_id);

// Create mapping from trait to placeholder.
let trait_to_placeholder_args =
impl_to_placeholder_args.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_args);
// Create mapping from trait to impl (i.e. impl trait header + impl method identity args).
let trait_to_impl_args = GenericArgs::identity_for_item(tcx, impl_m.def_id).rebase_onto(
tcx,
impl_m.container_id(tcx),
impl_trait_ref.args,
);

let hybrid_preds = tcx
.predicates_of(impl_m.container_id(tcx))
.instantiate_identity(tcx)
.into_iter()
.chain(tcx.predicates_of(trait_m.def_id).instantiate_own(tcx, trait_to_placeholder_args))
.chain(tcx.predicates_of(trait_m.def_id).instantiate_own(tcx, trait_to_impl_args))
.map(|(clause, _)| clause);
let param_env = ty::ParamEnv::new(tcx.mk_clauses_from_iter(hybrid_preds), Reveal::UserFacing);
let param_env = traits::normalize_param_env_or_error(
Expand Down Expand Up @@ -507,7 +500,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
.instantiate_binder_with_fresh_vars(
return_span,
infer::HigherRankedType,
tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_placeholder_args),
tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_impl_args),
)
.fold_with(&mut collector);

Expand Down Expand Up @@ -701,7 +694,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
// Also, we only need to account for a difference in trait and impl args,
// since we previously enforce that the trait method and impl method have the
// same generics.
let num_trait_args = trait_to_impl_args.len();
let num_trait_args = impl_trait_ref.args.len();
let num_impl_args = tcx.generics_of(impl_m.container_id(tcx)).own_params.len();
let ty = match ty.try_fold_with(&mut RemapHiddenTyRegions {
tcx,
Expand Down Expand Up @@ -1732,13 +1725,14 @@ fn compare_const_predicate_entailment<'tcx>(
// because we shouldn't really have to deal with lifetimes or
// predicates. In fact some of this should probably be put into
// shared functions because of DRY violations...
let impl_args = GenericArgs::identity_for_item(tcx, impl_ct.def_id);
let trait_to_impl_args =
impl_args.rebase_onto(tcx, impl_ct.container_id(tcx), impl_trait_ref.args);
let trait_to_impl_args = GenericArgs::identity_for_item(tcx, impl_ct.def_id).rebase_onto(
tcx,
impl_ct.container_id(tcx),
impl_trait_ref.args,
);

// Create a parameter environment that represents the implementation's
// method.
// Compute placeholder form of impl and trait const tys.
let impl_ty = tcx.type_of(impl_ct_def_id).instantiate_identity();

let trait_ty = tcx.type_of(trait_ct.def_id).instantiate(tcx, trait_to_impl_args);
Expand Down Expand Up @@ -1772,7 +1766,7 @@ fn compare_const_predicate_entailment<'tcx>(
let infcx = tcx.infer_ctxt().build();
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);

let impl_ct_own_bounds = impl_ct_predicates.instantiate_own(tcx, impl_args);
let impl_ct_own_bounds = impl_ct_predicates.instantiate_own_identity();
for (predicate, span) in impl_ct_own_bounds {
let cause = ObligationCause::misc(span, impl_ct_def_id);
let predicate = ocx.normalize(&cause, param_env, predicate);
Expand Down Expand Up @@ -1866,14 +1860,16 @@ fn compare_type_predicate_entailment<'tcx>(
trait_ty: ty::AssocItem,
impl_trait_ref: ty::TraitRef<'tcx>,
) -> Result<(), ErrorGuaranteed> {
let impl_args = GenericArgs::identity_for_item(tcx, impl_ty.def_id);
let trait_to_impl_args =
impl_args.rebase_onto(tcx, impl_ty.container_id(tcx), impl_trait_ref.args);
let trait_to_impl_args = GenericArgs::identity_for_item(tcx, impl_ty.def_id).rebase_onto(
tcx,
impl_ty.container_id(tcx),
impl_trait_ref.args,
);

let impl_ty_predicates = tcx.predicates_of(impl_ty.def_id);
let trait_ty_predicates = tcx.predicates_of(trait_ty.def_id);

let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_args);
let impl_ty_own_bounds = impl_ty_predicates.instantiate_own_identity();
if impl_ty_own_bounds.len() == 0 {
// Nothing to check.
return Ok(());
Expand Down
4 changes: 3 additions & 1 deletion compiler/rustc_middle/src/ty/generics.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -395,7 +395,9 @@ impl<'tcx> GenericPredicates<'tcx> {
EarlyBinder::bind(self.predicates).iter_instantiated_copied(tcx, args)
}

pub fn instantiate_own_identity(self) -> impl Iterator<Item = (Clause<'tcx>, Span)> {
pub fn instantiate_own_identity(
self,
) -> impl Iterator<Item = (Clause<'tcx>, Span)> + DoubleEndedIterator + ExactSizeIterator {
EarlyBinder::bind(self.predicates).iter_identity_copied()
}

Expand Down
42 changes: 40 additions & 2 deletions compiler/rustc_type_ir/src/binder.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -496,8 +496,8 @@ where

/// Similar to [`instantiate_identity`](EarlyBinder::instantiate_identity),
/// but on an iterator of values that deref to a `TypeFoldable`.
pub fn iter_identity_copied(self) -> impl Iterator<Item = <Iter::Item as Deref>::Target> {
self.value.into_iter().map(|v| *v)
pub fn iter_identity_copied(self) -> IterIdentityCopied<Iter> {
IterIdentityCopied { it: self.value.into_iter() }
}
}

Expand Down Expand Up @@ -546,6 +546,44 @@ where
{
}

pub struct IterIdentityCopied<Iter: IntoIterator> {
it: Iter::IntoIter,
}

impl<Iter: IntoIterator> Iterator for IterIdentityCopied<Iter>
where
Iter::Item: Deref,
<Iter::Item as Deref>::Target: Copy,
{
type Item = <Iter::Item as Deref>::Target;

fn next(&mut self) -> Option<Self::Item> {
self.it.next().map(|i| *i)
}

fn size_hint(&self) -> (usize, Option<usize>) {
self.it.size_hint()
}
}

impl<Iter: IntoIterator> DoubleEndedIterator for IterIdentityCopied<Iter>
where
Iter::IntoIter: DoubleEndedIterator,
Iter::Item: Deref,
<Iter::Item as Deref>::Target: Copy,
{
fn next_back(&mut self) -> Option<Self::Item> {
self.it.next_back().map(|i| *i)
}
}

impl<Iter: IntoIterator> ExactSizeIterator for IterIdentityCopied<Iter>
where
Iter::IntoIter: ExactSizeIterator,
Iter::Item: Deref,
<Iter::Item as Deref>::Target: Copy,
{
}
pub struct EarlyBinderIter<I, T> {
t: T,
_tcx: PhantomData<I>,
Expand Down

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