From 82e0bcafac723fdf5007a31a7ae74af1736c9f6f Mon Sep 17 00:00:00 2001
From: Matthew Brown <github@muglug.com>
Date: Fri, 26 Apr 2019 00:47:32 -0400
Subject: [PATCH] Fix #1578 - fix empty array error

---
 src/Psalm/Type/Union.php       |  2 +-
 tests/FileManipulationTest.php | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/Psalm/Type/Union.php b/src/Psalm/Type/Union.php
index 8d26489ba..ac6e1a250 100644
--- a/src/Psalm/Type/Union.php
+++ b/src/Psalm/Type/Union.php
@@ -1071,7 +1071,7 @@ class Union
                                     $new_generic_params = [];
 
                                     foreach ($extends_list as $key => $value) {
-                                        if (is_int($key)) {
+                                        if (is_string($key)) {
                                             $new_generic_params[] = $value;
                                         }
                                     }
diff --git a/tests/FileManipulationTest.php b/tests/FileManipulationTest.php
index 9a29866db..353964add 100644
--- a/tests/FileManipulationTest.php
+++ b/tests/FileManipulationTest.php
@@ -1796,6 +1796,27 @@ class FileManipulationTest extends TestCase
                 ['PossiblyUnusedMethod'],
                 true,
             ],
+            'dontRemovePossiblyUnusedMethodWithCallUserFuncCall' => [
+                '<?php
+                    class A {
+                        public function foo() : void {}
+                    }
+
+                    function foo(A $a, string $var) {
+                        call_user_func([$a, $var]);
+                    }',
+                '<?php
+                    class A {
+                        public function foo() : void {}
+                    }
+
+                    function foo(A $a, string $var) {
+                        call_user_func([$a, $var]);
+                    }',
+                '7.1',
+                ['PossiblyUnusedMethod'],
+                true,
+            ],
             'dontRemovePossiblyUnusedMethodWithVariableCallableLhsCall' => [
                 '<?php
                     class A {