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Instantiate binders when checking supertrait upcasting
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@compiler-errors
compiler-errors committed Sep 27, 2024
1 parent d4ee408 commit 4fb097a
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Showing 4 changed files with 132 additions and 48 deletions.
19 changes: 18 additions & 1 deletion compiler/rustc_infer/src/infer/at.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -159,7 +159,24 @@ impl<'a, 'tcx> At<'a, 'tcx> {
ToTrace::to_trace(self.cause, true, expected, actual),
self.param_env,
define_opaque_types,
);
ToTrace::to_trace(self.cause, expected, actual),
expected,
actual,
)
}

/// Makes `expected == actual`.
pub fn eq_trace<T>(
self,
define_opaque_types: DefineOpaqueTypes,
trace: TypeTrace<'tcx>,
expected: T,
actual: T,
) -> InferResult<'tcx, ()>
where
T: Relate<TyCtxt<'tcx>>,
{
let mut fields = CombineFields::new(self.infcx, trace, self.param_env, define_opaque_types);
fields.equate(StructurallyRelateAliases::No).relate(expected, actual)?;
Ok(InferOk {
value: (),
Expand Down
16 changes: 9 additions & 7 deletions compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -448,10 +448,10 @@ where
}
}
} else {
self.delegate.enter_forall(kind, |kind| {
let goal = goal.with(self.cx(), ty::Binder::dummy(kind));
self.add_goal(GoalSource::InstantiateHigherRanked, goal);
self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
self.enter_forall(kind, |ecx, kind| {
let goal = goal.with(ecx.cx(), ty::Binder::dummy(kind));
ecx.add_goal(GoalSource::InstantiateHigherRanked, goal);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
}
Expand Down Expand Up @@ -840,12 +840,14 @@ where
self.delegate.instantiate_binder_with_infer(value)
}

/// `enter_forall`, but takes `&mut self` and passes it back through the
/// callback since it can't be aliased during the call.
pub(super) fn enter_forall<T: TypeFoldable<I> + Copy, U>(
&self,
&mut self,
value: ty::Binder<I, T>,
f: impl FnOnce(T) -> U,
f: impl FnOnce(&mut Self, T) -> U,
) -> U {
self.delegate.enter_forall(value, f)
self.delegate.enter_forall(value, |value| f(self, value))
}

pub(super) fn resolve_vars_if_possible<T>(&self, value: T) -> T
Expand Down
49 changes: 29 additions & 20 deletions compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -895,10 +895,13 @@ where
source_projection.item_def_id() == target_projection.item_def_id()
&& ecx
.probe(|_| ProbeKind::UpcastProjectionCompatibility)
.enter(|ecx| -> Result<(), NoSolution> {
ecx.sub(param_env, source_projection, target_projection)?;
let _ = ecx.try_evaluate_added_goals()?;
Ok(())
.enter(|ecx| -> Result<_, NoSolution> {
ecx.enter_forall(target_projection, |ecx, target_projection| {
let source_projection =
ecx.instantiate_binder_with_infer(source_projection);
ecx.eq(param_env, source_projection, target_projection)?;
ecx.try_evaluate_added_goals()
})
})
.is_ok()
};
Expand All @@ -909,11 +912,14 @@ where
// Check that a's supertrait (upcast_principal) is compatible
// with the target (b_ty).
ty::ExistentialPredicate::Trait(target_principal) => {
ecx.sub(
param_env,
upcast_principal.unwrap(),
bound.rebind(target_principal),
)?;
let source_principal = upcast_principal.unwrap();
let target_principal = bound.rebind(target_principal);
ecx.enter_forall(target_principal, |ecx, target_principal| {
let source_principal =
ecx.instantiate_binder_with_infer(source_principal);
ecx.eq(param_env, source_principal, target_principal)?;
ecx.try_evaluate_added_goals()
})?;
}
// Check that b_ty's projection is satisfied by exactly one of
// a_ty's projections. First, we look through the list to see if
Expand All @@ -934,7 +940,12 @@ where
Certainty::AMBIGUOUS,
);
}
ecx.sub(param_env, source_projection, target_projection)?;
ecx.enter_forall(target_projection, |ecx, target_projection| {
let source_projection =
ecx.instantiate_binder_with_infer(source_projection);
ecx.eq(param_env, source_projection, target_projection)?;
ecx.try_evaluate_added_goals()
})?;
}
// Check that b_ty's auto traits are present in a_ty's bounds.
ty::ExistentialPredicate::AutoTrait(def_id) => {
Expand Down Expand Up @@ -1187,17 +1198,15 @@ where
) -> Result<Vec<ty::Binder<I, I::Ty>>, NoSolution>,
) -> Result<Candidate<I>, NoSolution> {
self.probe_trait_candidate(source).enter(|ecx| {
ecx.add_goals(
GoalSource::ImplWhereBound,
constituent_tys(ecx, goal.predicate.self_ty())?
.into_iter()
.map(|ty| {
ecx.enter_forall(ty, |ty| {
goal.with(ecx.cx(), goal.predicate.with_self_ty(ecx.cx(), ty))
})
let goals = constituent_tys(ecx, goal.predicate.self_ty())?
.into_iter()
.map(|ty| {
ecx.enter_forall(ty, |ecx, ty| {
goal.with(ecx.cx(), goal.predicate.with_self_ty(ecx.cx(), ty))
})
.collect::<Vec<_>>(),
);
})
.collect::<Vec<_>>();
ecx.add_goals(GoalSource::ImplWhereBound, goals);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
}
Expand Down
96 changes: 76 additions & 20 deletions compiler/rustc_trait_selection/src/traits/select/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ use rustc_hir::LangItem;
use rustc_hir::def_id::DefId;
use rustc_infer::infer::BoundRegionConversionTime::{self, HigherRankedType};
use rustc_infer::infer::DefineOpaqueTypes;
use rustc_infer::infer::at::ToTrace;
use rustc_infer::infer::relate::TypeRelation;
use rustc_infer::traits::TraitObligation;
use rustc_middle::bug;
Expand Down Expand Up @@ -44,7 +45,7 @@ use super::{
TraitQueryMode, const_evaluatable, project, util, wf,
};
use crate::error_reporting::InferCtxtErrorExt;
use crate::infer::{InferCtxt, InferCtxtExt, InferOk, TypeFreshener};
use crate::infer::{InferCtxt, InferOk, TypeFreshener};
use crate::solve::InferCtxtSelectExt as _;
use crate::traits::normalize::{normalize_with_depth, normalize_with_depth_to};
use crate::traits::project::{ProjectAndUnifyResult, ProjectionCacheKeyExt};
Expand Down Expand Up @@ -2579,16 +2580,32 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
// Check that a_ty's supertrait (upcast_principal) is compatible
// with the target (b_ty).
ty::ExistentialPredicate::Trait(target_principal) => {
let hr_source_principal = upcast_principal.map_bound(|trait_ref| {
ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
});
let hr_target_principal = bound.rebind(target_principal);

nested.extend(
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(
DefineOpaqueTypes::Yes,
bound.rebind(target_principal),
upcast_principal.map_bound(|trait_ref| {
ty::ExistentialTraitRef::erase_self_ty(tcx, trait_ref)
}),
)
.enter_forall(hr_target_principal, |target_principal| {
let source_principal =
self.infcx.instantiate_binder_with_fresh_vars(
obligation.cause.span,
HigherRankedType,
hr_source_principal,
);
self.infcx.at(&obligation.cause, obligation.param_env).eq_trace(
DefineOpaqueTypes::Yes,
ToTrace::to_trace(
&obligation.cause,
true,
hr_target_principal,
hr_source_principal,
),
target_principal,
source_principal,
)
})
.map_err(|_| SelectionError::Unimplemented)?
.into_obligations(),
);
Expand All @@ -2599,28 +2616,67 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
// return ambiguity. Otherwise, if exactly one matches, equate
// it with b_ty's projection.
ty::ExistentialPredicate::Projection(target_projection) => {
let target_projection = bound.rebind(target_projection);
let hr_target_projection = bound.rebind(target_projection);

let mut matching_projections =
a_data.projection_bounds().filter(|source_projection| {
a_data.projection_bounds().filter(|&hr_source_projection| {
// Eager normalization means that we can just use can_eq
// here instead of equating and processing obligations.
source_projection.item_def_id() == target_projection.item_def_id()
&& self.infcx.can_eq(
obligation.param_env,
*source_projection,
target_projection,
)
hr_source_projection.item_def_id() == hr_target_projection.item_def_id()
&& self.infcx.probe(|_| {
self.infcx
.enter_forall(hr_target_projection, |target_projection| {
let source_projection =
self.infcx.instantiate_binder_with_fresh_vars(
obligation.cause.span,
HigherRankedType,
hr_source_projection,
);
self.infcx
.at(&obligation.cause, obligation.param_env)
.eq_trace(
DefineOpaqueTypes::Yes,
ToTrace::to_trace(
&obligation.cause,
true,
hr_target_projection,
hr_source_projection,
),
target_projection,
source_projection,
)
})
.is_ok()
})
});
let Some(source_projection) = matching_projections.next() else {

let Some(hr_source_projection) = matching_projections.next() else {
return Err(SelectionError::Unimplemented);
};
if matching_projections.next().is_some() {
return Ok(None);
}
nested.extend(
self.infcx
.at(&obligation.cause, obligation.param_env)
.sup(DefineOpaqueTypes::Yes, target_projection, source_projection)
.enter_forall(hr_target_projection, |target_projection| {
let source_projection =
self.infcx.instantiate_binder_with_fresh_vars(
obligation.cause.span,
HigherRankedType,
hr_source_projection,
);
self.infcx.at(&obligation.cause, obligation.param_env).eq_trace(
DefineOpaqueTypes::Yes,
ToTrace::to_trace(
&obligation.cause,
true,
hr_target_projection,
hr_source_projection,
),
target_projection,
source_projection,
)
})
.map_err(|_| SelectionError::Unimplemented)?
.into_obligations(),
);
Expand Down

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