obligations_for_self_ty: skip irrelevant goals

Author: lcnr

compiler/rustc_hir_typeck/src/fn_ctxt/inspect_obligations.rs

@@ -37,10 +37,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> bool {
         match predicate.kind().skip_binder() {
             ty::PredicateKind::Clause(ty::ClauseKind::Trait(data)) => {
-                self.type_matches_expected_vid(expected_vid, data.self_ty())
+                self.type_matches_expected_vid(data.self_ty(), expected_vid)
             }
             ty::PredicateKind::Clause(ty::ClauseKind::Projection(data)) => {
-                self.type_matches_expected_vid(expected_vid, data.projection_term.self_ty())
+                self.type_matches_expected_vid(data.projection_term.self_ty(), expected_vid)
             }
             ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(..))
             | ty::PredicateKind::Subtype(..)
@@ -60,7 +60,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self), ret)]
-    fn type_matches_expected_vid(&self, expected_vid: ty::TyVid, ty: Ty<'tcx>) -> bool {
+    fn type_matches_expected_vid(&self, ty: Ty<'tcx>, expected_vid: ty::TyVid) -> bool {
         let ty = self.shallow_resolve(ty);
         debug!(?ty);
 
@@ -125,6 +125,18 @@ impl<'a, 'tcx> ProofTreeVisitor<'tcx> for NestedObligationsForSelfTy<'a, 'tcx> {
             return;
         }
 
+        // We don't care about any pending goals which don't actually
+        // use the self type.
+        if !inspect_goal
+            .orig_values()
+            .iter()
+            .filter_map(|arg| arg.as_type())
+            .any(|ty| self.fcx.type_matches_expected_vid(ty, self.self_ty))
+        {
+            debug!(goal = ?inspect_goal.goal(), "goal does not mention self type");
+            return;
+        }
+
         let tcx = self.fcx.tcx;
         let goal = inspect_goal.goal();
         if self.fcx.predicate_has_self_ty(goal.predicate, self.self_ty)

compiler/rustc_trait_selection/src/solve/inspect/analyse.rs

@@ -317,6 +317,10 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
         self.depth
     }
 
+    pub fn orig_values(&self) -> &[ty::GenericArg<'tcx>] {
+        &self.orig_values
+    }
+
     fn candidates_recur(
         &'a self,
         candidates: &mut Vec<InspectCandidate<'a, 'tcx>>,