Fix #2481

stubs/CoreGenericFunctions.phpstub

@@ -347,6 +347,22 @@ function array_merge_recursive(array ...$arrays)
 {
 }
 
+/**
+ * @psalm-pure
+ * 
+ * @no-named-arguments
+ *
+ * @psalm-template TKey as array-key
+ * @psalm-template TValue
+ *
+ * @param array<TKey, TValue> ...$arrays
+ *
+ * @return array<TKey, TValue>
+ */
+function array_merge(array ...$arrays)
+{
+}
+
 /**
  * @psalm-pure
  *

tests/ArrayFunctionCallTest.php

@@ -2768,6 +2768,13 @@ class ArrayFunctionCallTest extends TestCase
                     array_combine(["a", "b"], [1, 2, 3]);',
                 'error_message' => 'InvalidArgument',
             ],
+            'arrayMergeNoNamed' => [
+                'code' => '<?php
+                    $map = ["a" => []];
+                    array_merge(...$map);
+                ',
+                'error_message' => 'NamedArgumentNotAllowed'
+            ]
         ];
     }
 }