bjoernager/rust
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Do not project when there are unconstrained impl params

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This commit is contained in:
Michael Goulet 2025-01-03 05:01:14 +00:00
parent ab3924b298
commit 2d602ea793
26 changed files with 214 additions and 283 deletions
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63
compiler/rustc_trait_selection/src/traits/project.rs
View file

@ -950,39 +950,45 @@ fn assemble_candidates_from_impls<'cx, 'tcx>(
//
// NOTE: This should be kept in sync with the similar code in
// `rustc_ty_utils::instance::resolve_associated_item()`.
let node_item = specialization_graph::assoc_def(
match specialization_graph::assoc_def(
selcx.tcx(),
impl_data.impl_def_id,
obligation.predicate.def_id,
)
.map_err(|ErrorGuaranteed { .. }| ())?;
if node_item.is_final() {
// Non-specializable items are always projectable.
true
} else {
// Only reveal a specializable default if we're past type-checking
// and the obligation is monomorphic, otherwise passes such as
// transmute checking and polymorphic MIR optimizations could
// get a result which isn't correct for all monomorphizations.
match selcx.infcx.typing_mode() {
TypingMode::Coherence
| TypingMode::Analysis { .. }
| TypingMode::PostBorrowckAnalysis { .. } => {
debug!(
assoc_ty = ?selcx.tcx().def_path_str(node_item.item.def_id),
?obligation.predicate,
"assemble_candidates_from_impls: not eligible due to default",
);
false
}
TypingMode::PostAnalysis => {
// NOTE(eddyb) inference variables can resolve to parameters, so
// assume `poly_trait_ref` isn't monomorphic, if it contains any.
let poly_trait_ref = selcx.infcx.resolve_vars_if_possible(trait_ref);
!poly_trait_ref.still_further_specializable()
) {
Ok(node_item) => {
if node_item.is_final() {
// Non-specializable items are always projectable.
true
} else {
// Only reveal a specializable default if we're past type-checking
// and the obligation is monomorphic, otherwise passes such as
// transmute checking and polymorphic MIR optimizations could
// get a result which isn't correct for all monomorphizations.
match selcx.infcx.typing_mode() {
TypingMode::Coherence
| TypingMode::Analysis { .. }
| TypingMode::PostBorrowckAnalysis { .. } => {
debug!(
assoc_ty = ?selcx.tcx().def_path_str(node_item.item.def_id),
?obligation.predicate,
"not eligible due to default",
);
false
}
TypingMode::PostAnalysis => {
// NOTE(eddyb) inference variables can resolve to parameters, so
// assume `poly_trait_ref` isn't monomorphic, if it contains any.
let poly_trait_ref =
selcx.infcx.resolve_vars_if_possible(trait_ref);
!poly_trait_ref.still_further_specializable()
}
}
}
}
// Always project `ErrorGuaranteed`, since this will just help
// us propagate `TyKind::Error` around which suppresses ICEs
// and spurious, unrelated inference errors.
Err(ErrorGuaranteed { .. }) => true,
}
}
ImplSource::Builtin(BuiltinImplSource::Misc, _) => {
@ -2014,7 +2020,6 @@ fn confirm_impl_candidate<'cx, 'tcx>(
Ok(assoc_ty) => assoc_ty,
Err(guar) => return Progress::error(tcx, guar),
};
if !assoc_ty.item.defaultness(tcx).has_value() {
// This means that the impl is missing a definition for the
// associated type. This error will be reported by the type

14
compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
View file

@ -376,6 +376,12 @@ pub(crate) fn assoc_def(
// If there is no such item in that impl, this function will fail with a
// cycle error if the specialization graph is currently being built.
if let Some(&impl_item_id) = tcx.impl_item_implementor_ids(impl_def_id).get(&assoc_def_id) {
// Ensure that the impl is constrained, otherwise projection may give us
// bad unconstrained infer vars.
if let Some(impl_def_id) = impl_def_id.as_local() {
tcx.ensure().enforce_impl_non_lifetime_params_are_constrained(impl_def_id)?;
}
let item = tcx.associated_item(impl_item_id);
let impl_node = Node::Impl(impl_def_id);
return Ok(LeafDef {
@ -391,6 +397,14 @@ pub(crate) fn assoc_def(
let ancestors = trait_def.ancestors(tcx, impl_def_id)?;
if let Some(assoc_item) = ancestors.leaf_def(tcx, assoc_def_id) {
// Ensure that the impl is constrained, otherwise projection may give us
// bad unconstrained infer vars.
if assoc_item.item.container == ty::AssocItemContainer::Impl
&& let Some(impl_def_id) = assoc_item.item.container_id(tcx).as_local()
{
tcx.ensure().enforce_impl_non_lifetime_params_are_constrained(impl_def_id)?;
}
Ok(assoc_item)
} else {
// This is saying that neither the trait nor