From 1c2bc49838cb4d2bf45027b57e7e133d965263bf Mon Sep 17 00:00:00 2001
From: Bruce Weirdan <weirdan@gmail.com>
Date: Thu, 16 Feb 2023 01:28:47 -0400
Subject: [PATCH] Forbid non-null defaults for callable parameters

Fixes vimeo/psalm#3284
---
 .../Internal/Analyzer/FunctionLikeAnalyzer.php    | 15 +++++++++++++++
 tests/FunctionCallTest.php                        |  6 ++++++
 tests/MethodCallTest.php                          |  8 ++++++++
 3 files changed, 29 insertions(+)

diff --git a/src/Psalm/Internal/Analyzer/FunctionLikeAnalyzer.php b/src/Psalm/Internal/Analyzer/FunctionLikeAnalyzer.php
index 357bf57326b..152565c2862 100644
--- a/src/Psalm/Internal/Analyzer/FunctionLikeAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/FunctionLikeAnalyzer.php
@@ -1256,6 +1256,21 @@ private function processParams(
                         ),
                     );
                 }
+
+                if ($default_type
+                    && !$default_type->isNull()
+                    && $param_type->isSingleAndMaybeNullable()
+                    && $param_type->getCallableTypes()
+                ) {
+                    IssueBuffer::maybeAdd(
+                        new InvalidParamDefault(
+                            'Default value type for ' . $param_type->getId() . ' argument ' . ($offset + 1)
+                                . ' of method ' . $cased_method_id
+                                . ' can only be null, ' . $default_type->getId() . ' specified',
+                            $function_param->type_location,
+                        ),
+                    );
+                }
             }
 
             if ($has_template_types) {
diff --git a/tests/FunctionCallTest.php b/tests/FunctionCallTest.php
index 6c0a4f8a643..751590c7b1c 100644
--- a/tests/FunctionCallTest.php
+++ b/tests/FunctionCallTest.php
@@ -2741,6 +2741,12 @@ function takesArrayShapeWithZeroOrPositiveInt(array $foo): void
                 ',
                 'error_message' => 'RedundantFunctionCall',
             ],
+            'incorrectCallableParamDefault' => [
+                'code' => '<?php
+                    function foo(callable $_a = "strlen"): void {}
+                ',
+                'error_message' => 'InvalidParamDefault',
+            ],
         ];
     }
 
diff --git a/tests/MethodCallTest.php b/tests/MethodCallTest.php
index e308dbd6f08..e2030863f24 100644
--- a/tests/MethodCallTest.php
+++ b/tests/MethodCallTest.php
@@ -1562,6 +1562,14 @@ public function foo(): string {
                     }',
                 'error_message' => 'UndefinedMethod',
             ],
+            'incorrectCallableParamDefault' => [
+                'code' => '<?php
+                    class A {
+                        public function foo(callable $_a = "strlen"): void {}
+                    }
+                ',
+                'error_message' => 'InvalidParamDefault',
+            ],
         ];
     }
 }