From 4b16ae1609c65d337d4f22e2f4ddea0c4c467b3b Mon Sep 17 00:00:00 2001
From: Remy Rakic <remy.rakic@gmail.com>
Date: Tue, 19 Nov 2019 16:53:52 +0100
Subject: [PATCH] Add a way to list the base non-transitive edges in
 `TransitiveRelation`

---
 src/librustc_data_structures/transitive_relation.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/librustc_data_structures/transitive_relation.rs b/src/librustc_data_structures/transitive_relation.rs
index a3926c155517..bbf6999b9837 100644
--- a/src/librustc_data_structures/transitive_relation.rs
+++ b/src/librustc_data_structures/transitive_relation.rs
@@ -373,6 +373,14 @@ impl<T: Clone + Debug + Eq + Hash> TransitiveRelation<T> {
         }
         matrix
     }
+
+    /// Lists all the base edges in the graph: the initial _non-transitive_ set of element
+    /// relations, which will be later used as the basis for the transitive closure computation.
+    pub fn base_edges(&self) -> impl Iterator<Item=(&T, &T)> {
+        self.edges
+            .iter()
+            .map(move |edge| (&self.elements[edge.source.0], &self.elements[edge.target.0]))
+    }
 }
 
 /// Pare down is used as a step in the LUB computation. It edits the