Rollup merge of #112665 - compiler-errors:assumption-takes-clause, r=lcnr

Make assumption functions in new solver take `Binder<'tcx, Clause<'tcx>>`

We just use an if-let to match on an optional clause at all the places where we transition from `Predicate` -> `Clause`, but I assume that when things like item-bounds and param-env start to only store `Clause`s then those can just be trivially dropped.

r? ``@lcnr``

4 files changed, 98 insertions, 26 deletions

diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index 72341e656e2..ff5d99794f1 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -586,6 +586,24 @@ pub enum Clause<'tcx> {
     ConstArgHasType(Const<'tcx>, Ty<'tcx>),
 }
 
+impl<'tcx> Binder<'tcx, Clause<'tcx>> {
+    pub fn as_trait_clause(self) -> Option<Binder<'tcx, TraitPredicate<'tcx>>> {
+        if let ty::Clause::Trait(trait_clause) = self.skip_binder() {
+            Some(self.rebind(trait_clause))
+        } else {
+            None
+        }
+    }
+
+    pub fn as_projection_clause(self) -> Option<Binder<'tcx, ProjectionPredicate<'tcx>>> {
+        if let ty::Clause::Projection(projection_clause) = self.skip_binder() {
+            Some(self.rebind(projection_clause))
+        } else {
+            None
+        }
+    }
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub enum PredicateKind<'tcx> {
@@ -1203,6 +1221,17 @@ impl<'tcx> ToPredicate<'tcx> for TraitRef<'tcx> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Binder<'tcx, Clause<'tcx>>> for TraitRef<'tcx> {
+    #[inline(always)]
+    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Binder<'tcx, Clause<'tcx>> {
+        Binder::dummy(Clause::Trait(TraitPredicate {
+            trait_ref: self,
+            constness: ty::BoundConstness::NotConst,
+            polarity: ty::ImplPolarity::Positive,
+        }))
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
@@ -1211,6 +1240,14 @@ impl<'tcx> ToPredicate<'tcx> for Binder<'tcx, TraitRef<'tcx>> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Binder<'tcx, Clause<'tcx>>> for Binder<'tcx, TraitRef<'tcx>> {
+    #[inline(always)]
+    fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Binder<'tcx, Clause<'tcx>> {
+        let pred: PolyTraitPredicate<'tcx> = self.to_predicate(tcx);
+        pred.to_predicate(tcx)
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx, PolyTraitPredicate<'tcx>> for Binder<'tcx, TraitRef<'tcx>> {
     #[inline(always)]
     fn to_predicate(self, _: TyCtxt<'tcx>) -> PolyTraitPredicate<'tcx> {
@@ -1240,6 +1277,12 @@ impl<'tcx> ToPredicate<'tcx> for PolyTraitPredicate<'tcx> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Binder<'tcx, Clause<'tcx>>> for PolyTraitPredicate<'tcx> {
+    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Binder<'tcx, Clause<'tcx>> {
+        self.map_bound(|p| Clause::Trait(p))
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for PolyRegionOutlivesPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         self.map_bound(|p| PredicateKind::Clause(Clause::RegionOutlives(p))).to_predicate(tcx)
@@ -1258,6 +1301,12 @@ impl<'tcx> ToPredicate<'tcx> for PolyProjectionPredicate<'tcx> {
     }
 }
 
+impl<'tcx> ToPredicate<'tcx, Binder<'tcx, Clause<'tcx>>> for PolyProjectionPredicate<'tcx> {
+    fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> Binder<'tcx, Clause<'tcx>> {
+        self.map_bound(|p| Clause::Projection(p))
+    }
+}
+
 impl<'tcx> ToPredicate<'tcx> for TraitPredicate<'tcx> {
     fn to_predicate(self, tcx: TyCtxt<'tcx>) -> Predicate<'tcx> {
         PredicateKind::Clause(Clause::Trait(self)).to_predicate(tcx)
@@ -1327,6 +1376,23 @@ impl<'tcx> Predicate<'tcx> {
             | PredicateKind::TypeWellFormedFromEnv(..) => None,
         }
     }
+
+    pub fn as_clause(self) -> Option<Binder<'tcx, Clause<'tcx>>> {
+        let predicate = self.kind();
+        match predicate.skip_binder() {
+            PredicateKind::Clause(clause) => Some(predicate.rebind(clause)),
+            PredicateKind::AliasRelate(..)
+            | PredicateKind::Subtype(..)
+            | PredicateKind::Coerce(..)
+            | PredicateKind::WellFormed(..)
+            | PredicateKind::ObjectSafe(..)
+            | PredicateKind::ClosureKind(..)
+            | PredicateKind::ConstEvaluatable(..)
+            | PredicateKind::ConstEquate(..)
+            | PredicateKind::Ambiguous
+            | PredicateKind::TypeWellFormedFromEnv(..) => None,
+        }
+    }
 }
 
 /// Represents the bounds declared on a particular set of type
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index 1b749b9c854..e6eddf24844 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -105,7 +105,7 @@ pub(super) trait GoalKind<'tcx>:
     fn probe_and_match_goal_against_assumption(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
         then: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
     ) -> QueryResult<'tcx>;
 
@@ -115,7 +115,7 @@ pub(super) trait GoalKind<'tcx>:
     fn consider_implied_clause(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
         requirements: impl IntoIterator<Item = Goal<'tcx, ty::Predicate<'tcx>>>,
     ) -> QueryResult<'tcx> {
         Self::probe_and_match_goal_against_assumption(ecx, goal, assumption, |ecx| {
@@ -131,7 +131,7 @@ pub(super) trait GoalKind<'tcx>:
     fn consider_alias_bound_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
     ) -> QueryResult<'tcx> {
         Self::probe_and_match_goal_against_assumption(ecx, goal, assumption, |ecx| {
             ecx.validate_alias_bound_self_from_param_env(goal)
@@ -144,7 +144,7 @@ pub(super) trait GoalKind<'tcx>:
     fn consider_object_bound_candidate(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
     ) -> QueryResult<'tcx> {
         Self::probe_and_match_goal_against_assumption(ecx, goal, assumption, |ecx| {
             let tcx = ecx.tcx();
@@ -467,11 +467,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         candidates: &mut Vec<Candidate<'tcx>>,
     ) {
         for (i, assumption) in goal.param_env.caller_bounds().iter().enumerate() {
-            match G::consider_implied_clause(self, goal, assumption, []) {
-                Ok(result) => {
-                    candidates.push(Candidate { source: CandidateSource::ParamEnv(i), result })
+            if let Some(clause) = assumption.as_clause() {
+                match G::consider_implied_clause(self, goal, clause, []) {
+                    Ok(result) => {
+                        candidates.push(Candidate { source: CandidateSource::ParamEnv(i), result })
+                    }
+                    Err(NoSolution) => (),
                 }
-                Err(NoSolution) => (),
             }
         }
     }
@@ -517,11 +519,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
 
         for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
         {
-            match G::consider_alias_bound_candidate(self, goal, assumption) {
-                Ok(result) => {
-                    candidates.push(Candidate { source: CandidateSource::AliasBound, result })
+            if let Some(clause) = assumption.as_clause() {
+                match G::consider_alias_bound_candidate(self, goal, clause) {
+                    Ok(result) => {
+                        candidates.push(Candidate { source: CandidateSource::AliasBound, result })
+                    }
+                    Err(NoSolution) => (),
                 }
-                Err(NoSolution) => (),
             }
         }
     }
@@ -675,18 +679,20 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             // projection predicates that we reach by elaborating the principal trait ref,
             // since that'll cause ambiguity.
             //
-            // We can remove this when we have implemented intersections in responses.
+            // We can remove this when we have implemented lifetime intersections in responses.
             if assumption.to_opt_poly_projection_pred().is_some()
                 && !own_bounds.contains(&assumption)
             {
                 continue;
             }
 
-            match G::consider_object_bound_candidate(self, goal, assumption) {
-                Ok(result) => {
-                    candidates.push(Candidate { source: CandidateSource::BuiltinImpl, result })
+            if let Some(clause) = assumption.as_clause() {
+                match G::consider_object_bound_candidate(self, goal, clause) {
+                    Ok(result) => {
+                        candidates.push(Candidate { source: CandidateSource::BuiltinImpl, result })
+                    }
+                    Err(NoSolution) => (),
                 }
-                Err(NoSolution) => (),
             }
         }
     }
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index 242f9ba8747..8303bab4c36 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -105,15 +105,15 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
     fn probe_and_match_goal_against_assumption(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
         then: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
     ) -> QueryResult<'tcx> {
-        if let Some(poly_projection_pred) = assumption.to_opt_poly_projection_pred()
-            && poly_projection_pred.projection_def_id() == goal.predicate.def_id()
+        if let Some(projection_pred) = assumption.as_projection_clause()
+            && projection_pred.projection_def_id() == goal.predicate.def_id()
         {
             ecx.probe(|ecx| {
                 let assumption_projection_pred =
-                    ecx.instantiate_binder_with_infer(poly_projection_pred);
+                    ecx.instantiate_binder_with_infer(projection_pred);
                 ecx.eq(
                     goal.param_env,
                     goal.predicate.projection_ty,
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index f722f281314..60cf386a289 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -81,17 +81,17 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
     fn probe_and_match_goal_against_assumption(
         ecx: &mut EvalCtxt<'_, 'tcx>,
         goal: Goal<'tcx, Self>,
-        assumption: ty::Predicate<'tcx>,
+        assumption: ty::Binder<'tcx, ty::Clause<'tcx>>,
         then: impl FnOnce(&mut EvalCtxt<'_, 'tcx>) -> QueryResult<'tcx>,
     ) -> QueryResult<'tcx> {
-        if let Some(poly_trait_pred) = assumption.to_opt_poly_trait_pred()
-            && poly_trait_pred.def_id() == goal.predicate.def_id()
-            && poly_trait_pred.polarity() == goal.predicate.polarity
+        if let Some(trait_clause) = assumption.as_trait_clause()
+            && trait_clause.def_id() == goal.predicate.def_id()
+            && trait_clause.polarity() == goal.predicate.polarity
         {
             // FIXME: Constness
             ecx.probe(|ecx| {
                 let assumption_trait_pred =
-                    ecx.instantiate_binder_with_infer(poly_trait_pred);
+                    ecx.instantiate_binder_with_infer(trait_clause);
                 ecx.eq(
                     goal.param_env,
                     goal.predicate.trait_ref,