From dc0f2e7e462b19ca83b835f61dbe55063f30bdb0 Mon Sep 17 00:00:00 2001
From: Nils Adermann <naderman@naderman.de>
Date: Tue, 12 Nov 2019 22:19:32 +0100
Subject: [PATCH] Ensure multi conflict rules are only used for 3+ literals

Implements the equals method correctly on multi conflict rules. If there
are fewer literals a regular Rule2Literals is enough to represent the
basic conflict rule.
---
 src/Composer/DependencyResolver/MultiConflictRule.php | 9 ++++++++-
 src/Composer/DependencyResolver/RuleSetGenerator.php  | 4 ++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/Composer/DependencyResolver/MultiConflictRule.php b/src/Composer/DependencyResolver/MultiConflictRule.php
index 8ec6b46c0..d564ced2e 100644
--- a/src/Composer/DependencyResolver/MultiConflictRule.php
+++ b/src/Composer/DependencyResolver/MultiConflictRule.php
@@ -34,6 +34,10 @@ class MultiConflictRule extends Rule
     {
         parent::__construct($reason, $reasonData, $job);
 
+        if (count($literals) < 3) {
+            throw new \RuntimeException("multi conflict rule requires at least 3 literals");
+        }
+
         // sort all packages ascending by id
         sort($literals);
 
@@ -62,7 +66,10 @@ class MultiConflictRule extends Rule
      */
     public function equals(Rule $rule)
     {
-        return $this->literals === $rule->getLiterals();
+        if ($rule instanceof MultiConflictRule) {
+            return $this->literals === $rule->getLiterals();
+        }
+        return false;
     }
 
     public function isAssertion()
diff --git a/src/Composer/DependencyResolver/RuleSetGenerator.php b/src/Composer/DependencyResolver/RuleSetGenerator.php
index aaa253bed..442be135c 100644
--- a/src/Composer/DependencyResolver/RuleSetGenerator.php
+++ b/src/Composer/DependencyResolver/RuleSetGenerator.php
@@ -136,6 +136,10 @@ class RuleSetGenerator
             $literals[] = -$package->id;
         }
 
+        if (count($literals) == 2) {
+            return new Rule2Literals($literals[0], $literals[1], $reason, $reasonData);
+        }
+
         return new MultiConflictRule($literals, $reason, $reasonData);
     }