From 2cb85bda1bcf38b2d9f190531cace3c13b0b7f58 Mon Sep 17 00:00:00 2001
From: Dylan McGannon <me@dyl.dog>
Date: Sat, 1 Sep 2018 10:30:09 +1000
Subject: [PATCH] Maintain a list of visited FQNs while following extends to
 avoid loops.

---
 fixtures/self_referencing_class.php | 22 +++++++++++++++++++---
 src/DefinitionResolver.php          |  6 +++++-
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/fixtures/self_referencing_class.php b/fixtures/self_referencing_class.php
index 287fc25..06dc8f0 100644
--- a/fixtures/self_referencing_class.php
+++ b/fixtures/self_referencing_class.php
@@ -1,4 +1,20 @@
 <?php
-class C extends C {}
-$c = new C;
-$c->undef_prop = 1;
\ No newline at end of file
+namespace RecursiveTest;
+
+class A extends A {}
+
+class B extends C {}
+class C extends B {}
+
+class D extends E {}
+class E extends F {}
+class F extends D {}
+
+$a = new A;
+$a->undef_prop = 1;
+
+$b = new B;
+$b->undef_prop = 1;
+
+$d = new D;
+$d->undef_prop = 1;
diff --git a/src/DefinitionResolver.php b/src/DefinitionResolver.php
index 163000f..08b82aa 100644
--- a/src/DefinitionResolver.php
+++ b/src/DefinitionResolver.php
@@ -437,6 +437,7 @@ class DefinitionResolver
 
         // Find the right class that implements the member
         $implementorFqns = [$classFqn];
+        $visitedFqns = [];
 
         while ($implementorFqn = array_shift($implementorFqns)) {
             // If the member FQN exists, return it
@@ -449,10 +450,13 @@ class DefinitionResolver
             if ($implementorDef === null) {
                 break;
             }
+            // Note the FQN as visited
+            $visitedFqns[] = $implementorFqn;
             // Repeat for parent class
             if ($implementorDef->extends) {
                 foreach ($implementorDef->extends as $extends) {
-                    if ($extends !== $implementorFqn) {
+                    // Don't add the parent FQN if it's already been visited
+                    if (!\in_array($extends, $visitedFqns)) {
                         $implementorFqns[] = $extends;
                     }
                 }