Hook callback false positives for mixed return type

composer.json

@@ -56,7 +56,7 @@
         "test:cs": "phpcs",
         "test:cs:fix": "phpcbf",
         "test:phpstan": "phpstan analyze",
-        "test:phpunit": "phpunit",
+        "test:phpunit": "phpunit -d memory_limit=1G",
         "test:syntax": "parallel-lint bootstrap.php src/ tests/"
     }
 }

tests/HookCallbackRuleTest.php

@@ -116,6 +116,14 @@ public function testRule(): void
                     'Filter callback return statement is missing.',
                     99,
                 ],
+                [
+                    'Action callback returns mixed but should not return anything.',
+                    102,
+                ],
+                [
+                    'Action callback returns mixed but should not return anything.',
+                    105,
+                ],
             ]
         );
     }

tests/data/hook-callback.php

@@ -98,6 +98,12 @@
 // Filter callback return statement is missing.
 add_filter('filter', __NAMESPACE__ . '\\no_return_value_untyped');
 
+// Action callback returns mixed but should not return anything.
+add_action('action', __NAMESPACE__ . '\\return_value_mixed');
+
+// Action callback returns mixed but should not return anything.
+add_action('action', __NAMESPACE__ . '\\return_value_implicit_mixed');
+
 /**
  * Incorrect usage that's handled by PHPStan:
  *
@@ -214,6 +220,11 @@
 
 // Various callback types
 add_filter('filter', '__return_false');
+add_filter('filter', __NAMESPACE__ . '\\return_value_mixed');
+add_filter('filter', __NAMESPACE__ . '\\return_value_implicit_mixed');
+add_filter('filter', __NAMESPACE__ . '\\return_value_mixed_union');
+add_filter('filter', __NAMESPACE__ . '\\return_value_documented');
+add_filter('filter', __NAMESPACE__ . '\\return_value_untyped');
 add_filter('filter', __NAMESPACE__ . '\\return_value_typed');
 add_filter('filter', new TestInvokableTyped(), 10, 2);
 add_filter('filter', [new TestClassTyped, 'foo']);
@@ -240,6 +251,33 @@ function return_value_typed() : int {
 
 function no_return_value_untyped( $value ) {}
 
+/**
+ * @return mixed
+ */
+function return_value_mixed() {
+    return 123;
+}
+
+function return_value_implicit_mixed( $value ) {
+    return $value;
+}
+
+/**
+ * Return type documented as a union that includes mixed.
+ *
+ * @return int|mixed
+ */
+function return_value_mixed_union() {
+    return 123;
+}
+
+/**
+ * @return int
+ */
+function return_value_documented() {
+    return 123;
+}
+
 function return_value_untyped() {
     return 123;
 }