blob: 906cf14975002e11debe39dc4173d679bb53b4e5 [file] [log] [blame]
use crate::traits::specialization_graph;
use super::assembly::structural_traits::AsyncCallableRelevantTypes;
use super::assembly::{self, structural_traits, Candidate};
use super::{EvalCtxt, GoalSource};
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
use rustc_hir::LangItem;
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::solve::inspect::ProbeKind;
use rustc_infer::traits::solve::MaybeCause;
use rustc_infer::traits::specialization_graph::LeafDef;
use rustc_infer::traits::Reveal;
use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal, QueryResult};
use rustc_middle::traits::BuiltinImplSource;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams};
use rustc_middle::ty::NormalizesTo;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
use rustc_middle::{bug, span_bug};
use rustc_span::{sym, ErrorGuaranteed, DUMMY_SP};
mod anon_const;
mod inherent;
mod opaque_types;
mod weak_types;
impl<'tcx> EvalCtxt<'_, 'tcx> {
#[instrument(level = "trace", skip(self), ret)]
pub(super) fn compute_normalizes_to_goal(
&mut self,
goal: Goal<'tcx, NormalizesTo<'tcx>>,
) -> QueryResult<'tcx> {
self.set_is_normalizes_to_goal();
debug_assert!(self.term_is_fully_unconstrained(goal));
let normalize_result = self
.probe(|&result| ProbeKind::TryNormalizeNonRigid { result })
.enter(|this| this.normalize_at_least_one_step(goal));
match normalize_result {
Ok(res) => Ok(res),
Err(NoSolution) => {
let Goal { param_env, predicate: NormalizesTo { alias, term } } = goal;
if alias.opt_kind(self.tcx()).is_some() {
self.relate_rigid_alias_non_alias(
param_env,
alias,
ty::Variance::Invariant,
term,
)?;
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
} else {
// FIXME(generic_const_exprs): we currently do not support rigid
// unevaluated constants.
Err(NoSolution)
}
}
}
}
/// Normalize the given alias by at least one step. If the alias is rigid, this
/// returns `NoSolution`.
#[instrument(level = "trace", skip(self), ret)]
fn normalize_at_least_one_step(
&mut self,
goal: Goal<'tcx, NormalizesTo<'tcx>>,
) -> QueryResult<'tcx> {
let def_id = goal.predicate.def_id();
match self.tcx().def_kind(def_id) {
DefKind::AssocTy | DefKind::AssocConst => {
match self.tcx().associated_item(def_id).container {
ty::AssocItemContainer::TraitContainer => {
let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_candidates(candidates)
}
ty::AssocItemContainer::ImplContainer => {
self.normalize_inherent_associated_type(goal)
}
}
}
DefKind::AnonConst => self.normalize_anon_const(goal),
DefKind::TyAlias => self.normalize_weak_type(goal),
DefKind::OpaqueTy => self.normalize_opaque_type(goal),
kind => bug!("unknown DefKind {} in normalizes-to goal: {goal:#?}", kind.descr(def_id)),
}
}
/// When normalizing an associated item, constrain the expected term to `term`.
///
/// We know `term` to always be a fully unconstrained inference variable, so
/// `eq` should never fail here. However, in case `term` contains aliases, we
/// emit nested `AliasRelate` goals to structurally normalize the alias.
pub fn instantiate_normalizes_to_term(
&mut self,
goal: Goal<'tcx, NormalizesTo<'tcx>>,
term: ty::Term<'tcx>,
) {
self.eq(goal.param_env, goal.predicate.term, term)
.expect("expected goal term to be fully unconstrained");
}
}
impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
fn self_ty(self) -> Ty<'tcx> {
self.self_ty()
}
fn trait_ref(self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
self.alias.trait_ref(tcx)
}
fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
self.with_self_ty(tcx, self_ty)
}
fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId {
self.trait_def_id(tcx)
}
fn probe_and_match_goal_against_assumption(
ecx: &mut EvalCtxt<'_, 'tcx>,
source: CandidateSource,
goal: Goal<'tcx, Self>,
assumption: ty::Clause<'tcx>,
then: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
) -> Result<Candidate<'tcx>, NoSolution> {
if let Some(projection_pred) = assumption.as_projection_clause() {
if projection_pred.projection_def_id() == goal.predicate.def_id() {
let tcx = ecx.tcx();
ecx.probe_trait_candidate(source).enter(|ecx| {
let assumption_projection_pred =
ecx.instantiate_binder_with_infer(projection_pred);
ecx.eq(
goal.param_env,
goal.predicate.alias,
assumption_projection_pred.projection_ty,
)?;
ecx.instantiate_normalizes_to_term(goal, assumption_projection_pred.term);
// Add GAT where clauses from the trait's definition
ecx.add_goals(
GoalSource::Misc,
tcx.predicates_of(goal.predicate.def_id())
.instantiate_own(tcx, goal.predicate.alias.args)
.map(|(pred, _)| goal.with(tcx, pred)),
);
then(ecx)
})
} else {
Err(NoSolution)
}
} else {
Err(NoSolution)
}
}
fn consider_impl_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, NormalizesTo<'tcx>>,
impl_def_id: DefId,
) -> Result<Candidate<'tcx>, NoSolution> {
let tcx = ecx.tcx();
let goal_trait_ref = goal.predicate.alias.trait_ref(tcx);
let impl_trait_header = tcx.impl_trait_header(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
if !drcx.args_may_unify(
goal.predicate.trait_ref(tcx).args,
impl_trait_header.trait_ref.skip_binder().args,
) {
return Err(NoSolution);
}
// We have to ignore negative impls when projecting.
let impl_polarity = impl_trait_header.polarity;
match impl_polarity {
ty::ImplPolarity::Negative => return Err(NoSolution),
ty::ImplPolarity::Reservation => {
unimplemented!("reservation impl for trait with assoc item: {:?}", goal)
}
ty::ImplPolarity::Positive => {}
};
ecx.probe_trait_candidate(CandidateSource::Impl(impl_def_id)).enter(|ecx| {
let impl_args = ecx.fresh_args_for_item(impl_def_id);
let impl_trait_ref = impl_trait_header.trait_ref.instantiate(tcx, impl_args);
ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
let where_clause_bounds = tcx
.predicates_of(impl_def_id)
.instantiate(tcx, impl_args)
.predicates
.into_iter()
.map(|pred| goal.with(tcx, pred));
ecx.add_goals(GoalSource::ImplWhereBound, where_clause_bounds);
// Add GAT where clauses from the trait's definition
ecx.add_goals(
GoalSource::Misc,
tcx.predicates_of(goal.predicate.def_id())
.instantiate_own(tcx, goal.predicate.alias.args)
.map(|(pred, _)| goal.with(tcx, pred)),
);
// In case the associated item is hidden due to specialization, we have to
// return ambiguity this would otherwise be incomplete, resulting in
// unsoundness during coherence (#105782).
let Some(assoc_def) = fetch_eligible_assoc_item_def(
ecx,
goal.param_env,
goal_trait_ref,
goal.predicate.def_id(),
impl_def_id,
)?
else {
return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
};
let error_response = |ecx: &mut EvalCtxt<'_, 'tcx>, reason| {
let guar = tcx.dcx().span_delayed_bug(tcx.def_span(assoc_def.item.def_id), reason);
let error_term = match assoc_def.item.kind {
ty::AssocKind::Const => ty::Const::new_error(
tcx,
guar,
tcx.type_of(goal.predicate.def_id())
.instantiate(tcx, goal.predicate.alias.args),
)
.into(),
ty::AssocKind::Type => Ty::new_error(tcx, guar).into(),
// This makes no sense...
ty::AssocKind::Fn => span_bug!(
tcx.def_span(assoc_def.item.def_id),
"cannot project to an associated function"
),
};
ecx.instantiate_normalizes_to_term(goal, error_term);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
};
if !assoc_def.item.defaultness(tcx).has_value() {
return error_response(ecx, "missing value for assoc item in impl");
}
// Getting the right args here is complex, e.g. given:
// - a goal `<Vec<u32> as Trait<i32>>::Assoc<u64>`
// - the applicable impl `impl<T> Trait<i32> for Vec<T>`
// - and the impl which defines `Assoc` being `impl<T, U> Trait<U> for Vec<T>`
//
// We first rebase the goal args onto the impl, going from `[Vec<u32>, i32, u64]`
// to `[u32, u64]`.
//
// And then map these args to the args of the defining impl of `Assoc`, going
// from `[u32, u64]` to `[u32, i32, u64]`.
let impl_args_with_gat =
goal.predicate.alias.args.rebase_onto(tcx, goal_trait_ref.def_id, impl_args);
let args = ecx.translate_args(
goal.param_env,
impl_def_id,
impl_args_with_gat,
assoc_def.defining_node,
);
if !tcx.check_args_compatible(assoc_def.item.def_id, args) {
return error_response(
ecx,
"associated item has mismatched generic item arguments",
);
}
// Finally we construct the actual value of the associated type.
let term = match assoc_def.item.kind {
ty::AssocKind::Type => tcx.type_of(assoc_def.item.def_id).map_bound(|ty| ty.into()),
ty::AssocKind::Const => {
if tcx.features().associated_const_equality {
bug!("associated const projection is not supported yet")
} else {
ty::EarlyBinder::bind(
ty::Const::new_error_with_message(
tcx,
tcx.type_of(assoc_def.item.def_id).instantiate_identity(),
DUMMY_SP,
"associated const projection is not supported yet",
)
.into(),
)
}
}
ty::AssocKind::Fn => unreachable!("we should never project to a fn"),
};
ecx.instantiate_normalizes_to_term(goal, term.instantiate(tcx, args));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
/// Fail to normalize if the predicate contains an error, alternatively, we could normalize to `ty::Error`
/// and succeed. Can experiment with this to figure out what results in better error messages.
fn consider_error_guaranteed_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
_guar: ErrorGuaranteed,
) -> Result<Candidate<'tcx>, NoSolution> {
Err(NoSolution)
}
fn consider_auto_trait_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
ecx.tcx().dcx().span_delayed_bug(
ecx.tcx().def_span(goal.predicate.def_id()),
"associated types not allowed on auto traits",
);
Err(NoSolution)
}
fn consider_trait_alias_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("trait aliases do not have associated types: {:?}", goal);
}
fn consider_builtin_sized_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`Sized` does not have an associated type: {:?}", goal);
}
fn consider_builtin_copy_clone_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`Copy`/`Clone` does not have an associated type: {:?}", goal);
}
fn consider_builtin_pointer_like_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`PointerLike` does not have an associated type: {:?}", goal);
}
fn consider_builtin_fn_ptr_trait_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`FnPtr` does not have an associated type: {:?}", goal);
}
fn consider_builtin_fn_trait_candidates(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
goal_kind: ty::ClosureKind,
) -> Result<Candidate<'tcx>, NoSolution> {
let tcx = ecx.tcx();
let tupled_inputs_and_output =
match structural_traits::extract_tupled_inputs_and_output_from_callable(
tcx,
goal.predicate.self_ty(),
goal_kind,
)? {
Some(tupled_inputs_and_output) => tupled_inputs_and_output,
None => {
return ecx.forced_ambiguity(MaybeCause::Ambiguity);
}
};
let output_is_sized_pred = tupled_inputs_and_output.map_bound(|(_, output)| {
ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, None), [output])
});
let pred = tupled_inputs_and_output
.map_bound(|(inputs, output)| ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(
tcx,
goal.predicate.def_id(),
[goal.predicate.self_ty(), inputs],
),
term: output.into(),
})
.to_predicate(tcx);
// A built-in `Fn` impl only holds if the output is sized.
// (FIXME: technically we only need to check this if the type is a fn ptr...)
Self::probe_and_consider_implied_clause(
ecx,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
goal,
pred,
[(GoalSource::ImplWhereBound, goal.with(tcx, output_is_sized_pred))],
)
}
fn consider_builtin_async_fn_trait_candidates(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
goal_kind: ty::ClosureKind,
) -> Result<Candidate<'tcx>, NoSolution> {
let tcx = ecx.tcx();
let env_region = match goal_kind {
ty::ClosureKind::Fn | ty::ClosureKind::FnMut => goal.predicate.alias.args.region_at(2),
// Doesn't matter what this region is
ty::ClosureKind::FnOnce => tcx.lifetimes.re_static,
};
let (tupled_inputs_and_output_and_coroutine, nested_preds) =
structural_traits::extract_tupled_inputs_and_output_from_async_callable(
tcx,
goal.predicate.self_ty(),
goal_kind,
env_region,
)?;
let output_is_sized_pred = tupled_inputs_and_output_and_coroutine.map_bound(
|AsyncCallableRelevantTypes { output_coroutine_ty: output_ty, .. }| {
ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, None), [output_ty])
},
);
let pred = tupled_inputs_and_output_and_coroutine
.map_bound(
|AsyncCallableRelevantTypes {
tupled_inputs_ty,
output_coroutine_ty,
coroutine_return_ty,
}| {
let (projection_ty, term) = match tcx.item_name(goal.predicate.def_id()) {
sym::CallOnceFuture => (
ty::AliasTy::new(
tcx,
goal.predicate.def_id(),
[goal.predicate.self_ty(), tupled_inputs_ty],
),
output_coroutine_ty.into(),
),
sym::CallRefFuture => (
ty::AliasTy::new(
tcx,
goal.predicate.def_id(),
[
ty::GenericArg::from(goal.predicate.self_ty()),
tupled_inputs_ty.into(),
env_region.into(),
],
),
output_coroutine_ty.into(),
),
sym::Output => (
ty::AliasTy::new(
tcx,
goal.predicate.def_id(),
[
ty::GenericArg::from(goal.predicate.self_ty()),
tupled_inputs_ty.into(),
],
),
coroutine_return_ty.into(),
),
name => bug!("no such associated type: {name}"),
};
ty::ProjectionPredicate { projection_ty, term }
},
)
.to_predicate(tcx);
// A built-in `AsyncFn` impl only holds if the output is sized.
// (FIXME: technically we only need to check this if the type is a fn ptr...)
Self::probe_and_consider_implied_clause(
ecx,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
goal,
pred,
[goal.with(tcx, output_is_sized_pred)]
.into_iter()
.chain(nested_preds.into_iter().map(|pred| goal.with(tcx, pred)))
.map(|goal| (GoalSource::ImplWhereBound, goal)),
)
}
fn consider_builtin_async_fn_kind_helper_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let [
closure_fn_kind_ty,
goal_kind_ty,
borrow_region,
tupled_inputs_ty,
tupled_upvars_ty,
coroutine_captures_by_ref_ty,
] = **goal.predicate.alias.args
else {
bug!();
};
// Bail if the upvars haven't been constrained.
if tupled_upvars_ty.expect_ty().is_ty_var() {
return ecx.forced_ambiguity(MaybeCause::Ambiguity);
}
let Some(closure_kind) = closure_fn_kind_ty.expect_ty().to_opt_closure_kind() else {
// We don't need to worry about the self type being an infer var.
return Err(NoSolution);
};
let Some(goal_kind) = goal_kind_ty.expect_ty().to_opt_closure_kind() else {
return Err(NoSolution);
};
if !closure_kind.extends(goal_kind) {
return Err(NoSolution);
}
let upvars_ty = ty::CoroutineClosureSignature::tupled_upvars_by_closure_kind(
ecx.tcx(),
goal_kind,
tupled_inputs_ty.expect_ty(),
tupled_upvars_ty.expect_ty(),
coroutine_captures_by_ref_ty.expect_ty(),
borrow_region.expect_region(),
);
ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
ecx.instantiate_normalizes_to_term(goal, upvars_ty.into());
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_tuple_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`Tuple` does not have an associated type: {:?}", goal);
}
fn consider_builtin_pointee_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let tcx = ecx.tcx();
let metadata_def_id = tcx.require_lang_item(LangItem::Metadata, None);
assert_eq!(metadata_def_id, goal.predicate.def_id());
ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
let metadata_ty = match goal.predicate.self_ty().kind() {
ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Array(..)
| ty::Pat(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Infer(ty::IntVar(..) | ty::FloatVar(..))
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Foreign(..)
| ty::Dynamic(_, _, ty::DynStar) => tcx.types.unit,
ty::Error(e) => Ty::new_error(tcx, *e),
ty::Str | ty::Slice(_) => tcx.types.usize,
ty::Dynamic(_, _, ty::Dyn) => {
let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
tcx.type_of(dyn_metadata)
.instantiate(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
}
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
// This is the "fallback impl" for type parameters, unnormalizable projections
// and opaque types: If the `self_ty` is `Sized`, then the metadata is `()`.
// FIXME(ptr_metadata): This impl overlaps with the other impls and shouldn't
// exist. Instead, `Pointee<Metadata = ()>` should be a supertrait of `Sized`.
let sized_predicate = ty::TraitRef::new(
tcx,
tcx.require_lang_item(LangItem::Sized, None),
[ty::GenericArg::from(goal.predicate.self_ty())],
);
// FIXME(-Znext-solver=coinductive): Should this be `GoalSource::ImplWhereBound`?
ecx.add_goal(GoalSource::Misc, goal.with(tcx, sized_predicate));
tcx.types.unit
}
ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
None => tcx.types.unit,
Some(tail_def) => {
let tail_ty = tail_def.ty(tcx, args);
Ty::new_projection(tcx, metadata_def_id, [tail_ty])
}
},
ty::Adt(_, _) => tcx.types.unit,
ty::Tuple(elements) => match elements.last() {
None => tcx.types.unit,
Some(&tail_ty) => Ty::new_projection(tcx, metadata_def_id, [tail_ty]),
},
ty::Infer(
ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_),
)
| ty::Bound(..) => bug!(
"unexpected self ty `{:?}` when normalizing `<T as Pointee>::Metadata`",
goal.predicate.self_ty()
),
};
ecx.instantiate_normalizes_to_term(goal, metadata_ty.into());
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_future_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let ty::Coroutine(def_id, args) = *self_ty.kind() else {
return Err(NoSolution);
};
// Coroutines are not futures unless they come from `async` desugaring
let tcx = ecx.tcx();
if !tcx.coroutine_is_async(def_id) {
return Err(NoSolution);
}
let term = args.as_coroutine().return_ty().into();
Self::probe_and_consider_implied_clause(
ecx,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
goal,
ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
term,
}
.to_predicate(tcx),
// Technically, we need to check that the future type is Sized,
// but that's already proven by the coroutine being WF.
[],
)
}
fn consider_builtin_iterator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let ty::Coroutine(def_id, args) = *self_ty.kind() else {
return Err(NoSolution);
};
// Coroutines are not Iterators unless they come from `gen` desugaring
let tcx = ecx.tcx();
if !tcx.coroutine_is_gen(def_id) {
return Err(NoSolution);
}
let term = args.as_coroutine().yield_ty().into();
Self::probe_and_consider_implied_clause(
ecx,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
goal,
ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(ecx.tcx(), goal.predicate.def_id(), [self_ty]),
term,
}
.to_predicate(tcx),
// Technically, we need to check that the iterator type is Sized,
// but that's already proven by the generator being WF.
[],
)
}
fn consider_builtin_fused_iterator_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`FusedIterator` does not have an associated type: {:?}", goal);
}
fn consider_builtin_async_iterator_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let ty::Coroutine(def_id, args) = *self_ty.kind() else {
return Err(NoSolution);
};
// Coroutines are not AsyncIterators unless they come from `gen` desugaring
let tcx = ecx.tcx();
if !tcx.coroutine_is_async_gen(def_id) {
return Err(NoSolution);
}
ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
let expected_ty = ecx.next_ty_infer();
// Take `AsyncIterator<Item = I>` and turn it into the corresponding
// coroutine yield ty `Poll<Option<I>>`.
let wrapped_expected_ty = Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(LangItem::Poll, None)),
tcx.mk_args(&[Ty::new_adt(
tcx,
tcx.adt_def(tcx.require_lang_item(LangItem::Option, None)),
tcx.mk_args(&[expected_ty.into()]),
)
.into()]),
);
let yield_ty = args.as_coroutine().yield_ty();
ecx.eq(goal.param_env, wrapped_expected_ty, yield_ty)?;
ecx.instantiate_normalizes_to_term(goal, expected_ty.into());
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_coroutine_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let ty::Coroutine(def_id, args) = *self_ty.kind() else {
return Err(NoSolution);
};
// `async`-desugared coroutines do not implement the coroutine trait
let tcx = ecx.tcx();
if !tcx.is_general_coroutine(def_id) {
return Err(NoSolution);
}
let coroutine = args.as_coroutine();
let name = tcx.associated_item(goal.predicate.def_id()).name;
let term = if name == sym::Return {
coroutine.return_ty().into()
} else if name == sym::Yield {
coroutine.yield_ty().into()
} else {
bug!("unexpected associated item `<{self_ty} as Coroutine>::{name}`")
};
Self::probe_and_consider_implied_clause(
ecx,
CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
goal,
ty::ProjectionPredicate {
projection_ty: ty::AliasTy::new(
ecx.tcx(),
goal.predicate.def_id(),
[self_ty, coroutine.resume_ty()],
),
term,
}
.to_predicate(tcx),
// Technically, we need to check that the coroutine type is Sized,
// but that's already proven by the coroutine being WF.
[],
)
}
fn consider_structural_builtin_unsize_candidates(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Vec<Candidate<'tcx>> {
bug!("`Unsize` does not have an associated type: {:?}", goal);
}
fn consider_builtin_discriminant_kind_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let discriminant_ty = match *self_ty.kind() {
ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Array(..)
| ty::Pat(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Infer(ty::IntVar(..) | ty::FloatVar(..))
| ty::Coroutine(..)
| ty::CoroutineWitness(..)
| ty::Never
| ty::Foreign(..)
| ty::Adt(_, _)
| ty::Str
| ty::Slice(_)
| ty::Dynamic(_, _, _)
| ty::Tuple(_)
| ty::Error(_) => self_ty.discriminant_ty(ecx.tcx()),
// We do not call `Ty::discriminant_ty` on alias, param, or placeholder
// types, which return `<self_ty as DiscriminantKind>::Discriminant`
// (or ICE in the case of placeholders). Projecting a type to itself
// is never really productive.
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
return Err(NoSolution);
}
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Bound(..) => bug!(
"unexpected self ty `{:?}` when normalizing `<T as DiscriminantKind>::Discriminant`",
goal.predicate.self_ty()
),
};
ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
ecx.instantiate_normalizes_to_term(goal, discriminant_ty.into());
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_async_destruct_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
let self_ty = goal.predicate.self_ty();
let async_destructor_ty = match *self_ty.kind() {
ty::Bool
| ty::Char
| ty::Int(..)
| ty::Uint(..)
| ty::Float(..)
| ty::Array(..)
| ty::RawPtr(..)
| ty::Ref(..)
| ty::FnDef(..)
| ty::FnPtr(..)
| ty::Closure(..)
| ty::CoroutineClosure(..)
| ty::Infer(ty::IntVar(..) | ty::FloatVar(..))
| ty::Never
| ty::Adt(_, _)
| ty::Str
| ty::Slice(_)
| ty::Tuple(_)
| ty::Error(_) => self_ty.async_destructor_ty(ecx.tcx(), goal.param_env),
// We do not call `Ty::async_destructor_ty` on alias, param, or placeholder
// types, which return `<self_ty as AsyncDestruct>::AsyncDestructor`
// (or ICE in the case of placeholders). Projecting a type to itself
// is never really productive.
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
return Err(NoSolution);
}
ty::Infer(ty::TyVar(_) | ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_))
| ty::Foreign(..)
| ty::Bound(..) => bug!(
"unexpected self ty `{:?}` when normalizing `<T as AsyncDestruct>::AsyncDestructor`",
goal.predicate.self_ty()
),
ty::Pat(..) | ty::Dynamic(..) | ty::Coroutine(..) | ty::CoroutineWitness(..) => bug!(
"`consider_builtin_async_destruct_candidate` is not yet implemented for type: {self_ty:?}"
),
};
ecx.probe_builtin_trait_candidate(BuiltinImplSource::Misc).enter(|ecx| {
ecx.eq(goal.param_env, goal.predicate.term, async_destructor_ty.into())
.expect("expected goal term to be fully unconstrained");
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_destruct_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`Destruct` does not have an associated type: {:?}", goal);
}
fn consider_builtin_transmute_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Candidate<'tcx>, NoSolution> {
bug!("`BikeshedIntrinsicFrom` does not have an associated type: {:?}", goal)
}
}
/// This behavior is also implemented in `rustc_ty_utils` and in the old `project` code.
///
/// FIXME: We should merge these 3 implementations as it's likely that they otherwise
/// diverge.
#[instrument(level = "trace", skip(ecx, param_env), ret)]
fn fetch_eligible_assoc_item_def<'tcx>(
ecx: &EvalCtxt<'_, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
goal_trait_ref: ty::TraitRef<'tcx>,
trait_assoc_def_id: DefId,
impl_def_id: DefId,
) -> Result<Option<LeafDef>, NoSolution> {
let node_item = specialization_graph::assoc_def(ecx.tcx(), impl_def_id, trait_assoc_def_id)
.map_err(|ErrorGuaranteed { .. }| NoSolution)?;
let eligible = 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.
if param_env.reveal() == Reveal::All {
let poly_trait_ref = ecx.resolve_vars_if_possible(goal_trait_ref);
!poly_trait_ref.still_further_specializable()
} else {
trace!(?node_item.item.def_id, "not eligible due to default");
false
}
};
if eligible { Ok(Some(node_item)) } else { Ok(None) }
}