From fcf0a681d94e97a8a329a0aa8d66a68f900a16b2 Mon Sep 17 00:00:00 2001
From: Brown <github@muglug.com>
Date: Sat, 6 Jun 2020 10:33:49 -0400
Subject: [PATCH] Fix #3531 - ignore mixed returns from template

---
 .../Analyzer/Statements/ReturnAnalyzer.php    |  4 ++++
 tests/Template/ClassTemplateExtendsTest.php   | 24 +++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php
index d6fc70af7..cfdb3952b 100644
--- a/src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/ReturnAnalyzer.php
@@ -289,6 +289,10 @@ class ReturnAnalyzer
                         return null;
                     }
 
+                    if ($local_return_type->isMixed()) {
+                        return null;
+                    }
+
                     if (!$context->collect_initializations
                         && !$context->collect_mutations
                         && $statements_analyzer->getFilePath() === $statements_analyzer->getRootFilePath()
diff --git a/tests/Template/ClassTemplateExtendsTest.php b/tests/Template/ClassTemplateExtendsTest.php
index d01d8da1a..71a0644c5 100644
--- a/tests/Template/ClassTemplateExtendsTest.php
+++ b/tests/Template/ClassTemplateExtendsTest.php
@@ -4114,6 +4114,30 @@ class ClassTemplateExtendsTest extends TestCase
                         takesSubjects($subjects);
                     }'
             ],
+            'implementMixedReturnNull' => [
+                '<?php
+                    /** @template T */
+                    interface Templated {
+                        /** @return T */
+                        public function foo();
+                    }
+
+                    class Concrete implements Templated {
+                        private array $t;
+
+                        public function __construct(array $t) {
+                            $this->t = $t;
+                        }
+
+                        public function foo() {
+                            if (rand(0, 1)) {
+                                return null;
+                            }
+
+                            return $this->t;
+                        }
+                    }'
+            ],
         ];
     }