diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 47fc5f00755..915d722dd02 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -253,17 +253,6 @@ pub(super) trait GoalKind<'tcx>:
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Vec<(CanonicalResponse<'tcx>, BuiltinImplSource)>;
-
- /// Consider the `Unsize` candidate corresponding to coercing a sized type
- /// into a `dyn Trait`.
- ///
- /// This is computed separately from the rest of the `Unsize` candidates
- /// since it is only done once per self type, and not once per
- /// *normalization step* (in `assemble_candidates_via_self_ty`).
- fn consider_unsize_to_dyn_candidate(
- ecx: &mut EvalCtxt<'_, 'tcx>,
- goal: Goal<'tcx, Self>,
- ) -> QueryResult<'tcx>;
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
@@ -306,8 +295,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
self.assemble_object_bound_candidates(goal, &mut candidates);
- self.assemble_unsize_to_dyn_candidate(goal, &mut candidates);
-
self.assemble_blanket_impl_candidates(goal, &mut candidates);
self.assemble_param_env_candidates(goal, &mut candidates);
@@ -422,24 +409,6 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
- #[instrument(level = "debug", skip_all)]
- fn assemble_unsize_to_dyn_candidate<G: GoalKind<'tcx>>(
- &mut self,
- goal: Goal<'tcx, G>,
- candidates: &mut Vec<Candidate<'tcx>>,
- ) {
- let tcx = self.tcx();
- if tcx.lang_items().unsize_trait() == Some(goal.predicate.trait_def_id(tcx)) {
- match G::consider_unsize_to_dyn_candidate(self, goal) {
- Ok(result) => candidates.push(Candidate {
- source: CandidateSource::BuiltinImpl(BuiltinImplSource::Misc),
- result,
- }),
- Err(NoSolution) => (),
- }
- }
- }
-
#[instrument(level = "debug", skip_all)]
fn assemble_blanket_impl_candidates<G: GoalKind<'tcx>>(
&mut self,
diff --git a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
index ccee6f8eb29..9f1b4a09a20 100644
--- a/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalizes_to/mod.rs
@@ -603,13 +603,6 @@ impl<'tcx> assembly::GoalKind<'tcx> for NormalizesTo<'tcx> {
)
}
- fn consider_unsize_to_dyn_candidate(
- _ecx: &mut EvalCtxt<'_, 'tcx>,
- goal: Goal<'tcx, Self>,
- ) -> QueryResult<'tcx> {
- bug!("`Unsize` does not have an associated type: {:?}", goal)
- }
-
fn consider_structural_builtin_unsize_candidates(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index be079275684..b185e4e5f8e 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -490,53 +490,6 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
ecx.evaluate_added_goals_and_make_canonical_response(certainty)
}
- fn consider_unsize_to_dyn_candidate(
- ecx: &mut EvalCtxt<'_, 'tcx>,
- goal: Goal<'tcx, Self>,
- ) -> QueryResult<'tcx> {
- ecx.probe(|_| ProbeKind::UnsizeAssembly).enter(|ecx| {
- let a_ty = goal.predicate.self_ty();
- // We need to normalize the b_ty since it's destructured as a `dyn Trait`.
- let Some(b_ty) =
- ecx.try_normalize_ty(goal.param_env, goal.predicate.trait_ref.args.type_at(1))
- else {
- return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::OVERFLOW);
- };
-
- let ty::Dynamic(b_data, b_region, ty::Dyn) = *b_ty.kind() else {
- return Err(NoSolution);
- };
-
- let tcx = ecx.tcx();
-
- // Can only unsize to an object-safe trait.
- if b_data.principal_def_id().is_some_and(|def_id| !tcx.check_is_object_safe(def_id)) {
- return Err(NoSolution);
- }
-
- // Check that the type implements all of the predicates of the trait object.
- // (i.e. the principal, all of the associated types match, and any auto traits)
- ecx.add_goals(
- GoalSource::ImplWhereBound,
- b_data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
- );
-
- // The type must be `Sized` to be unsized.
- if let Some(sized_def_id) = tcx.lang_items().sized_trait() {
- ecx.add_goal(
- GoalSource::ImplWhereBound,
- goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])),
- );
- } else {
- return Err(NoSolution);
- }
-
- // The type must outlive the lifetime of the `dyn` we're unsizing into.
- ecx.add_goal(GoalSource::Misc, goal.with(tcx, ty::OutlivesPredicate(a_ty, b_region)));
- ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
- })
- }
-
/// ```ignore (builtin impl example)
/// trait Trait {
/// fn foo(&self);
@@ -588,8 +541,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
goal, a_data, a_region, b_data, b_region,
),
- // `T` -> `dyn Trait` unsizing is handled separately in `consider_unsize_to_dyn_candidate`
- (_, &ty::Dynamic(..)) => vec![],
+ // `T` -> `dyn Trait` unsizing.
+ (_, &ty::Dynamic(b_region, b_data, ty::Dyn)) => result_to_single(
+ ecx.consider_builtin_unsize_to_dyn_candidate(goal, b_region, b_data),
+ BuiltinImplSource::Misc,
+ ),
// `[T; N]` -> `[T]` unsizing
(&ty::Array(a_elem_ty, ..), &ty::Slice(b_elem_ty)) => result_to_single(
@@ -691,6 +647,42 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
responses
}
+ fn consider_builtin_unsize_to_dyn_candidate(
+ &mut self,
+ goal: Goal<'tcx, (Ty<'tcx>, Ty<'tcx>)>,
+ b_data: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
+ b_region: ty::Region<'tcx>,
+ ) -> QueryResult<'tcx> {
+ let tcx = self.tcx();
+ let Goal { predicate: (a_ty, _), .. } = goal;
+
+ // Can only unsize to an object-safe trait.
+ if b_data.principal_def_id().is_some_and(|def_id| !tcx.check_is_object_safe(def_id)) {
+ return Err(NoSolution);
+ }
+
+ // Check that the type implements all of the predicates of the trait object.
+ // (i.e. the principal, all of the associated types match, and any auto traits)
+ self.add_goals(
+ GoalSource::ImplWhereBound,
+ b_data.iter().map(|pred| goal.with(tcx, pred.with_self_ty(tcx, a_ty))),
+ );
+
+ // The type must be `Sized` to be unsized.
+ if let Some(sized_def_id) = tcx.lang_items().sized_trait() {
+ self.add_goal(
+ GoalSource::ImplWhereBound,
+ goal.with(tcx, ty::TraitRef::new(tcx, sized_def_id, [a_ty])),
+ );
+ } else {
+ return Err(NoSolution);
+ }
+
+ // The type must outlive the lifetime of the `dyn` we're unsizing into.
+ self.add_goal(GoalSource::Misc, goal.with(tcx, ty::OutlivesPredicate(a_ty, b_region)));
+ self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
+ }
+
fn consider_builtin_upcast_to_principal(
&mut self,
goal: Goal<'tcx, (Ty<'tcx>, Ty<'tcx>)>,