From f6bfe283ddbd31a0cc91c50fe53ddbffd59f5884 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 2 May 2024 13:51:13 -0400
Subject: [PATCH] Super visitor

---
 compiler/rustc_trait_selection/src/solve/fulfill.rs | 13 ++++---------
 .../src/solve/inspect/analyse.rs                    |  8 ++++++++
 2 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/compiler/rustc_trait_selection/src/solve/fulfill.rs b/compiler/rustc_trait_selection/src/solve/fulfill.rs
index d4fde60fd4a72..8e1095e0353dd 100644
--- a/compiler/rustc_trait_selection/src/solve/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/solve/fulfill.rs
@@ -219,14 +219,14 @@ fn fulfillment_error_for_no_solution<'tcx>(
         }
         ty::PredicateKind::Subtype(pred) => {
             let (a, b) = infcx.enter_forall_and_leak_universe(
-                root_obligation.predicate.kind().rebind((pred.a, pred.b)),
+                obligation.predicate.kind().rebind((pred.a, pred.b)),
             );
             let expected_found = ExpectedFound::new(true, a, b);
             FulfillmentErrorCode::SubtypeError(expected_found, TypeError::Sorts(expected_found))
         }
         ty::PredicateKind::Coerce(pred) => {
             let (a, b) = infcx.enter_forall_and_leak_universe(
-                root_obligation.predicate.kind().rebind((pred.a, pred.b)),
+                obligation.predicate.kind().rebind((pred.a, pred.b)),
             );
             let expected_found = ExpectedFound::new(false, a, b);
             FulfillmentErrorCode::SubtypeError(expected_found, TypeError::Sorts(expected_found))
@@ -298,13 +298,8 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
     }
 
     fn visit_goal(&mut self, goal: &super::inspect::InspectGoal<'_, 'tcx>) -> Self::Result {
-        let candidates = goal.candidates();
         // FIXME: Throw out candidates that have no failing WC and >1 failing misc goal.
-
-        // HACK:
-        if self.obligation.recursion_depth > 3 {
-            return ControlFlow::Break(self.obligation.clone());
-        }
+        let candidates = goal.candidates();
 
         let [candidate] = candidates.as_slice() else {
             return ControlFlow::Break(self.obligation.clone());
@@ -376,7 +371,7 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
                         recursion_depth: self_.obligation.recursion_depth + 1,
                     }
                 },
-                |self_| self_.visit_goal(&nested_goal),
+                |self_| nested_goal.visit_with(self),
             )?;
         }
 
diff --git a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
index de6c2322e8d8d..70a52d9fe7f53 100644
--- a/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
+++ b/compiler/rustc_trait_selection/src/solve/inspect/analyse.rs
@@ -360,6 +360,14 @@ impl<'a, 'tcx> InspectGoal<'a, 'tcx> {
             source,
         }
     }
+
+    pub(crate) fn visit_with<V: ProofTreeVisitor<'tcx>>(&self, visitor: &mut V) -> V::Result {
+        if self.goal.depth < visitor.config().max_depth {
+            try_visit!(visitor.visit_goal(self));
+        }
+
+        V::Result::output()
+    }
 }
 
 /// The public API to interact with proof trees.