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Auto merge of #113329 - lcnr:probe_candidate, r=BoxyUwU

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add `ecx.probe_candidate`

Not yet changing the candidate source to an enum because that would be more involved, but this by itself should already be a significant improvement imo

r? `@BoxyUwU`
This commit is contained in:
bors 2023-07-05 03:50:36 +00:00
commit 9227ff28af
5 changed files with 276 additions and 294 deletions
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68
compiler/rustc_trait_selection/src/solve/alias_relate.rs
View File

@ -1,6 +1,5 @@
use super::{EvalCtxt, SolverMode};
use rustc_infer::traits::query::NoSolution;
use rustc_middle::traits::solve::inspect::CandidateKind;
use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
use rustc_middle::ty;
@ -110,12 +109,10 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
direction: ty::AliasRelationDirection,
invert: Invert,
) -> QueryResult<'tcx> {
self.probe(|r| CandidateKind::Candidate { name: "normalizes-to".into(), result: *r }).enter(
|ecx| {
ecx.normalizes_to_inner(param_env, alias, other, direction, invert)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
},
)
self.probe_candidate("normalizes-to").enter(|ecx| {
ecx.normalizes_to_inner(param_env, alias, other, direction, invert)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn normalizes_to_inner(
@ -156,20 +153,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
alias_rhs: ty::AliasTy<'tcx>,
direction: ty::AliasRelationDirection,
) -> QueryResult<'tcx> {
self.probe(|r| CandidateKind::Candidate { name: "substs relate".into(), result: *r }).enter(
|ecx| {
match direction {
ty::AliasRelationDirection::Equate => {
ecx.eq(param_env, alias_lhs, alias_rhs)?;
}
ty::AliasRelationDirection::Subtype => {
ecx.sub(param_env, alias_lhs, alias_rhs)?;
}
self.probe_candidate("substs relate").enter(|ecx| {
match direction {
ty::AliasRelationDirection::Equate => {
ecx.eq(param_env, alias_lhs, alias_rhs)?;
}
ty::AliasRelationDirection::Subtype => {
ecx.sub(param_env, alias_lhs, alias_rhs)?;
}
}
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
},
)
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn assemble_bidirectional_normalizes_to_candidate(
@ -179,23 +174,22 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
rhs: ty::Term<'tcx>,
direction: ty::AliasRelationDirection,
) -> QueryResult<'tcx> {
self.probe(|r| CandidateKind::Candidate { name: "bidir normalizes-to".into(), result: *r })
.enter(|ecx| {
ecx.normalizes_to_inner(
param_env,
lhs.to_alias_ty(ecx.tcx()).unwrap(),
rhs,
direction,
Invert::No,
)?;
ecx.normalizes_to_inner(
param_env,
rhs.to_alias_ty(ecx.tcx()).unwrap(),
lhs,
direction,
Invert::Yes,
)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
self.probe_candidate("bidir normalizes-to").enter(|ecx| {
ecx.normalizes_to_inner(
param_env,
lhs.to_alias_ty(ecx.tcx()).unwrap(),
rhs,
direction,
Invert::No,
)?;
ecx.normalizes_to_inner(
param_env,
rhs.to_alias_ty(ecx.tcx()).unwrap(),
lhs,
direction,
Invert::Yes,
)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
}

34
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
View File

@ -9,7 +9,7 @@ use rustc_infer::infer::{
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::ObligationCause;
use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
use rustc_middle::traits::solve::inspect::{self, CandidateKind};
use rustc_middle::traits::solve::inspect;
use rustc_middle::traits::solve::{
CanonicalInput, CanonicalResponse, Certainty, IsNormalizesToHack, MaybeCause,
PredefinedOpaques, PredefinedOpaquesData, QueryResult,
@ -895,25 +895,19 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
if candidate_key.def_id != key.def_id {
continue;
}
values.extend(
self.probe(|r| CandidateKind::Candidate {
name: "opaque type storage".into(),
result: *r,
})
.enter(|ecx| {
for (a, b) in std::iter::zip(candidate_key.substs, key.substs) {
ecx.eq(param_env, a, b)?;
}
ecx.eq(param_env, candidate_ty, ty)?;
ecx.add_item_bounds_for_hidden_type(
candidate_key.def_id.to_def_id(),
candidate_key.substs,
param_env,
candidate_ty,
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}),
);
values.extend(self.probe_candidate("opaque type storage").enter(|ecx| {
for (a, b) in std::iter::zip(candidate_key.substs, key.substs) {
ecx.eq(param_env, a, b)?;
}
ecx.eq(param_env, candidate_ty, ty)?;
ecx.add_item_bounds_for_hidden_type(
candidate_key.def_id.to_def_id(),
candidate_key.substs,
param_env,
candidate_ty,
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}));
}
values
}

22
compiler/rustc_trait_selection/src/solve/eval_ctxt/probe.rs
View File

@ -1,5 +1,5 @@
use super::EvalCtxt;
use rustc_middle::traits::solve::inspect;
use rustc_middle::traits::solve::{inspect, QueryResult};
use std::marker::PhantomData;
pub(in crate::solve) struct ProbeCtxt<'me, 'a, 'tcx, F, T> {
@ -44,4 +44,24 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
{
ProbeCtxt { ecx: self, probe_kind, _result: PhantomData }
}
pub(in crate::solve) fn probe_candidate(
&mut self,
name: &'static str,
) -> ProbeCtxt<
'_,
'a,
'tcx,
impl FnOnce(&QueryResult<'tcx>) -> inspect::CandidateKind<'tcx>,
QueryResult<'tcx>,
> {
ProbeCtxt {
ecx: self,
probe_kind: move |result: &QueryResult<'tcx>| inspect::CandidateKind::Candidate {
name: name.to_string(),
result: *result,
},
_result: PhantomData,
}
}
}

171
compiler/rustc_trait_selection/src/solve/project_goals.rs
View File

@ -112,23 +112,18 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
) -> QueryResult<'tcx> {
if let Some(projection_pred) = assumption.as_projection_clause() {
if projection_pred.projection_def_id() == goal.predicate.def_id() {
ecx.probe(|r| CandidateKind::Candidate { name: "assumption".into(), result: *r })
.enter(|ecx| {
let assumption_projection_pred =
ecx.instantiate_binder_with_infer(projection_pred);
ecx.eq(
goal.param_env,
goal.predicate.projection_ty,
assumption_projection_pred.projection_ty,
)?;
ecx.eq(
goal.param_env,
goal.predicate.term,
assumption_projection_pred.term,
)
ecx.probe_candidate("assumption").enter(|ecx| {
let assumption_projection_pred =
ecx.instantiate_binder_with_infer(projection_pred);
ecx.eq(
goal.param_env,
goal.predicate.projection_ty,
assumption_projection_pred.projection_ty,
)?;
ecx.eq(goal.param_env, goal.predicate.term, assumption_projection_pred.term)
.expect("expected goal term to be fully unconstrained");
then(ecx)
})
then(ecx)
})
} else {
Err(NoSolution)
}
@ -328,69 +323,53 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
goal: Goal<'tcx, Self>,
) -> QueryResult<'tcx> {
let tcx = ecx.tcx();
ecx.probe(|r| CandidateKind::Candidate { name: "builtin pointee".into(), result: *r })
.enter(|ecx| {
let metadata_ty = match goal.predicate.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::Infer(ty::IntVar(..) | ty::FloatVar(..))
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::GeneratorWitnessMIR(..)
| ty::Never
| ty::Foreign(..) => tcx.types.unit,
ecx.probe_candidate("builtin pointee").enter(|ecx| {
let metadata_ty = match goal.predicate.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::Infer(ty::IntVar(..) | ty::FloatVar(..))
| ty::Generator(..)
| ty::GeneratorWitness(..)
| ty::GeneratorWitnessMIR(..)
| ty::Never
| ty::Foreign(..) => tcx.types.unit,
ty::Error(e) => tcx.ty_error(*e),
ty::Error(e) => tcx.ty_error(*e),
ty::Str | ty::Slice(_) => tcx.types.usize,
ty::Str | ty::Slice(_) => tcx.types.usize,
ty::Dynamic(_, _, _) => {
let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
tcx.type_of(dyn_metadata)
.subst(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
}
ty::Dynamic(_, _, _) => {
let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
tcx.type_of(dyn_metadata)
.subst(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
}
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
// FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints.
let sized_predicate = ty::TraitRef::from_lang_item(
tcx,
LangItem::Sized,
DUMMY_SP,
[ty::GenericArg::from(goal.predicate.self_ty())],
);
ecx.add_goal(goal.with(tcx, sized_predicate));
tcx.types.unit
}
ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
// FIXME(ptr_metadata): It would also be possible to return a `Ok(Ambig)` with no constraints.
let sized_predicate = ty::TraitRef::from_lang_item(
tcx,
LangItem::Sized,
DUMMY_SP,
[ty::GenericArg::from(goal.predicate.self_ty())],
);
ecx.add_goal(goal.with(tcx, sized_predicate));
tcx.types.unit
}
ty::Adt(def, substs) if def.is_struct() => {
match def.non_enum_variant().fields.raw.last() {
None => tcx.types.unit,
Some(field_def) => {
let self_ty = field_def.ty(tcx, substs);
ecx.add_goal(goal.with(
tcx,
ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)),
));
return ecx.evaluate_added_goals_and_make_canonical_response(
Certainty::Yes,
);
}
}
}
ty::Adt(_, _) => tcx.types.unit,
ty::Tuple(elements) => match elements.last() {
ty::Adt(def, substs) if def.is_struct() => {
match def.non_enum_variant().fields.raw.last() {
None => tcx.types.unit,
Some(&self_ty) => {
Some(field_def) => {
let self_ty = field_def.ty(tcx, substs);
ecx.add_goal(goal.with(
tcx,
ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)),
@ -398,21 +377,35 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
return ecx
.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
}
},
}
}
ty::Adt(_, _) => tcx.types.unit,
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()
),
};
ty::Tuple(elements) => match elements.last() {
None => tcx.types.unit,
Some(&self_ty) => {
ecx.add_goal(goal.with(
tcx,
ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)),
));
return ecx
.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
}
},
ecx.eq(goal.param_env, goal.predicate.term, metadata_ty.into())
.expect("expected goal term to be fully unconstrained");
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
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.eq(goal.param_env, goal.predicate.term, metadata_ty.into())
.expect("expected goal term to be fully unconstrained");
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_future_candidate(
@ -547,11 +540,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
),
};
ecx.probe(|r| CandidateKind::Candidate {
name: "builtin discriminant kind".into(),
result: *r,
})
.enter(|ecx| {
ecx.probe_candidate("builtin discriminant kind").enter(|ecx| {
ecx.eq(goal.param_env, goal.predicate.term, discriminant_ty.into())
.expect("expected goal term to be fully unconstrained");
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)

275
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -6,7 +6,6 @@ use rustc_hir::def_id::DefId;
use rustc_hir::{LangItem, Movability};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::util::supertraits;
use rustc_middle::traits::solve::inspect::CandidateKind;
use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections};
use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
@ -62,7 +61,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
},
};
ecx.probe(|r| CandidateKind::Candidate { name: "impl".into(), result: *r }).enter(|ecx| {
ecx.probe_candidate("impl").enter(|ecx| {
let impl_substs = ecx.fresh_substs_for_item(impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
@ -90,16 +89,15 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
&& trait_clause.polarity() == goal.predicate.polarity
{
// FIXME: Constness
ecx.probe(|r| CandidateKind::Candidate { name: "assumption".into(), result: *r })
.enter(|ecx| {
let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause);
ecx.eq(
goal.param_env,
goal.predicate.trait_ref,
assumption_trait_pred.trait_ref,
)?;
then(ecx)
})
ecx.probe_candidate("assumption").enter(|ecx| {
let assumption_trait_pred = ecx.instantiate_binder_with_infer(trait_clause);
ecx.eq(
goal.param_env,
goal.predicate.trait_ref,
assumption_trait_pred.trait_ref,
)?;
then(ecx)
})
} else {
Err(NoSolution)
}
@ -136,15 +134,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
let tcx = ecx.tcx();
ecx.probe(|r| CandidateKind::Candidate { name: "trait alias".into(), result: *r }).enter(
|ecx| {
let nested_obligations = tcx
.predicates_of(goal.predicate.def_id())
.instantiate(tcx, goal.predicate.trait_ref.substs);
ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
},
)
ecx.probe_candidate("trait alias").enter(|ecx| {
let nested_obligations = tcx
.predicates_of(goal.predicate.def_id())
.instantiate(tcx, goal.predicate.trait_ref.substs);
ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
fn consider_builtin_sized_candidate(
@ -350,115 +346,109 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
if b_ty.is_ty_var() {
return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
}
ecx.probe(|r| CandidateKind::Candidate { name: "builtin unsize".into(), result: *r }).enter(
|ecx| {
match (a_ty.kind(), b_ty.kind()) {
// Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b`
(&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => {
// Dyn upcasting is handled separately, since due to upcasting,
// when there are two supertraits that differ by substs, we
// may return more than one query response.
Err(NoSolution)
ecx.probe_candidate("builtin unsize").enter(|ecx| {
match (a_ty.kind(), b_ty.kind()) {
// Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b`
(&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => {
// Dyn upcasting is handled separately, since due to upcasting,
// when there are two supertraits that differ by substs, we
// may return more than one query response.
Err(NoSolution)
}
// `T` -> `dyn Trait` unsizing
(_, &ty::Dynamic(data, region, ty::Dyn)) => {
// Can only unsize to an object-safe type
if data
.principal_def_id()
.is_some_and(|def_id| !tcx.check_is_object_safe(def_id))
{
return Err(NoSolution);
}
// `T` -> `dyn Trait` unsizing
(_, &ty::Dynamic(data, region, ty::Dyn)) => {
// Can only unsize to an object-safe type
if data
.principal_def_id()
.is_some_and(|def_id| !tcx.check_is_object_safe(def_id))
{
return Err(NoSolution);
}
let Some(sized_def_id) = tcx.lang_items().sized_trait() else {
let Some(sized_def_id) = tcx.lang_items().sized_trait() else {
return Err(NoSolution);
};
// Check that the type implements all of the predicates of the def-id.
// (i.e. the principal, all of the associated types match, and any auto traits)
ecx.add_goals(
data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
);
// The type must be Sized to be unsized.
ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])));
// The type must outlive the lifetime of the `dyn` we're unsizing into.
ecx.add_goal(
goal.with(tcx, ty::Binder::dummy(ty::OutlivesPredicate(a_ty, region))),
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
// `[T; n]` -> `[T]` unsizing
(&ty::Array(a_elem_ty, ..), &ty::Slice(b_elem_ty)) => {
// We just require that the element type stays the same
ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
// Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>`
(&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
if a_def.is_struct() && a_def.did() == b_def.did() =>
{
let unsizing_params = tcx.unsizing_params_for_adt(a_def.did());
// We must be unsizing some type parameters. This also implies
// that the struct has a tail field.
if unsizing_params.is_empty() {
return Err(NoSolution);
}
let tail_field = a_def
.non_enum_variant()
.fields
.raw
.last()
.expect("expected unsized ADT to have a tail field");
let tail_field_ty = tcx.type_of(tail_field.did);
let a_tail_ty = tail_field_ty.subst(tcx, a_substs);
let b_tail_ty = tail_field_ty.subst(tcx, b_substs);
// Substitute just the unsizing params from B into A. The type after
// this substitution must be equal to B. This is so we don't unsize
// unrelated type parameters.
let new_a_substs =
tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| {
if unsizing_params.contains(i as u32) { b_substs[i] } else { a }
}));
let unsized_a_ty = tcx.mk_adt(a_def, new_a_substs);
// Finally, we require that `TailA: Unsize<TailB>` for the tail field
// types.
ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
ecx.add_goal(goal.with(
tcx,
ty::TraitRef::new(tcx, goal.predicate.def_id(), [a_tail_ty, b_tail_ty]),
));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
// Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize<U>`
(&ty::Tuple(a_tys), &ty::Tuple(b_tys))
if a_tys.len() == b_tys.len() && !a_tys.is_empty() =>
{
let (a_last_ty, a_rest_tys) = a_tys.split_last().unwrap();
let b_last_ty = b_tys.last().unwrap();
// Substitute just the tail field of B., and require that they're equal.
let unsized_a_ty =
tcx.mk_tup_from_iter(a_rest_tys.iter().chain([b_last_ty]).copied());
ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
// Similar to ADTs, require that the rest of the fields are equal.
ecx.add_goal(goal.with(
tcx,
ty::TraitRef::new(
tcx,
goal.predicate.def_id(),
[*a_last_ty, *b_last_ty],
),
));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
_ => Err(NoSolution),
// Check that the type implements all of the predicates of the def-id.
// (i.e. the principal, all of the associated types match, and any auto traits)
ecx.add_goals(
data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
);
// The type must be Sized to be unsized.
ecx.add_goal(goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])));
// The type must outlive the lifetime of the `dyn` we're unsizing into.
ecx.add_goal(
goal.with(tcx, ty::Binder::dummy(ty::OutlivesPredicate(a_ty, region))),
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
},
)
// `[T; n]` -> `[T]` unsizing
(&ty::Array(a_elem_ty, ..), &ty::Slice(b_elem_ty)) => {
// We just require that the element type stays the same
ecx.eq(goal.param_env, a_elem_ty, b_elem_ty)?;
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
// Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>`
(&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
if a_def.is_struct() && a_def.did() == b_def.did() =>
{
let unsizing_params = tcx.unsizing_params_for_adt(a_def.did());
// We must be unsizing some type parameters. This also implies
// that the struct has a tail field.
if unsizing_params.is_empty() {
return Err(NoSolution);
}
let tail_field = a_def
.non_enum_variant()
.fields
.raw
.last()
.expect("expected unsized ADT to have a tail field");
let tail_field_ty = tcx.type_of(tail_field.did);
let a_tail_ty = tail_field_ty.subst(tcx, a_substs);
let b_tail_ty = tail_field_ty.subst(tcx, b_substs);
// Substitute just the unsizing params from B into A. The type after
// this substitution must be equal to B. This is so we don't unsize
// unrelated type parameters.
let new_a_substs =
tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| {
if unsizing_params.contains(i as u32) { b_substs[i] } else { a }
}));
let unsized_a_ty = tcx.mk_adt(a_def, new_a_substs);
// Finally, we require that `TailA: Unsize<TailB>` for the tail field
// types.
ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
ecx.add_goal(goal.with(
tcx,
ty::TraitRef::new(tcx, goal.predicate.def_id(), [a_tail_ty, b_tail_ty]),
));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
// Tuple unsizing `(.., T)` -> `(.., U)` where `T: Unsize<U>`
(&ty::Tuple(a_tys), &ty::Tuple(b_tys))
if a_tys.len() == b_tys.len() && !a_tys.is_empty() =>
{
let (a_last_ty, a_rest_tys) = a_tys.split_last().unwrap();
let b_last_ty = b_tys.last().unwrap();
// Substitute just the tail field of B., and require that they're equal.
let unsized_a_ty =
tcx.mk_tup_from_iter(a_rest_tys.iter().chain([b_last_ty]).copied());
ecx.eq(goal.param_env, unsized_a_ty, b_ty)?;
// Similar to ADTs, require that the rest of the fields are equal.
ecx.add_goal(goal.with(
tcx,
ty::TraitRef::new(tcx, goal.predicate.def_id(), [*a_last_ty, *b_last_ty]),
));
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
}
_ => Err(NoSolution),
}
})
}
fn consider_builtin_dyn_upcast_candidates(
@ -488,11 +478,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
}
let mut unsize_dyn_to_principal = |principal: Option<ty::PolyExistentialTraitRef<'tcx>>| {
ecx.probe(|r| CandidateKind::Candidate {
name: "upcast dyn to principle".into(),
result: *r,
})
.enter(|ecx| -> Result<_, NoSolution> {
ecx.probe_candidate("upcast dyn to principle").enter(|ecx| -> Result<_, NoSolution> {
// Require that all of the trait predicates from A match B, except for
// the auto traits. We do this by constructing a new A type with B's
// auto traits, and equating these types.
@ -714,21 +700,20 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
goal: Goal<'tcx, TraitPredicate<'tcx>>,
constituent_tys: impl Fn(&EvalCtxt<'_, 'tcx>, Ty<'tcx>) -> Result<Vec<Ty<'tcx>>, NoSolution>,
) -> QueryResult<'tcx> {
self.probe(|r| CandidateKind::Candidate { name: "constituent tys".into(), result: *r })
.enter(|ecx| {
ecx.add_goals(
constituent_tys(ecx, goal.predicate.self_ty())?
.into_iter()
.map(|ty| {
goal.with(
ecx.tcx(),
ty::Binder::dummy(goal.predicate.with_self_ty(ecx.tcx(), ty)),
)
})
.collect::<Vec<_>>(),
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
self.probe_candidate("constituent tys").enter(|ecx| {
ecx.add_goals(
constituent_tys(ecx, goal.predicate.self_ty())?
.into_iter()
.map(|ty| {
goal.with(
ecx.tcx(),
ty::Binder::dummy(goal.predicate.with_self_ty(ecx.tcx(), ty)),
)
})
.collect::<Vec<_>>(),
);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
#[instrument(level = "debug", skip(self))]