Initial support for named parameters for callables

src/Psalm/Internal/Type/ParseTree/CallableParamTree.php

@@ -12,4 +12,11 @@ final class CallableParamTree extends ParseTree
     public bool $variadic = false;
 
     public bool $has_default = false;
+
+    /**
+     * Param name, without the $ prefix
+     *
+     * @var null|non-empty-string
+     */
+    public ?string $name = null;
 }

src/Psalm/Internal/Type/ParseTreeCreator.php

@@ -30,6 +30,7 @@
 use function preg_match;
 use function strlen;
 use function strtolower;
+use function substr;
 
 /**
  * @internal
@@ -258,13 +259,17 @@ private function parseCallableParam(array $current_token, ParseTree $current_par
             $current_token = $this->t < $this->type_token_count ? $this->type_tokens[$this->t] : null;
         }
 
-        if (!$current_token || $current_token[0][0] !== '$') {
+        if (!$current_token || $current_token[0][0] !== '$' || strlen($current_token[0]) < 2) {
             throw new TypeParseTreeException('Unexpected token after space');
         }
 
         $new_leaf = new CallableParamTree($current_parent);
         $new_leaf->has_default = $has_default;
         $new_leaf->variadic = $variadic;
+        $potential_name = substr($current_token[0], 1);
+        if ($potential_name !== false && $potential_name !== '') {
+            $new_leaf->name = $potential_name;
+        }
 
         if ($current_parent !== $this->current_leaf) {
             $new_leaf->children = [$this->current_leaf];

src/Psalm/Internal/Type/TypeParser.php

@@ -1277,6 +1277,7 @@ private static function getTypeFromCallableTree(
         foreach ($parse_tree->children as $child_tree) {
             $is_variadic = false;
             $is_optional = false;
+            $param_name = '';
 
             if ($child_tree instanceof CallableParamTree) {
                 if (isset($child_tree->children[0])) {
@@ -1294,6 +1295,7 @@ private static function getTypeFromCallableTree(
 
                 $is_variadic = $child_tree->variadic;
                 $is_optional = $child_tree->has_default;
+                $param_name = $child_tree->name ?? '';
             } else {
                 if ($child_tree instanceof Value && strpos($child_tree->value, '$') > 0) {
                     $child_tree->value = preg_replace('/(.+)\$.*/', '$1', $child_tree->value);
@@ -1310,7 +1312,7 @@ private static function getTypeFromCallableTree(
             }
 
             $param = new FunctionLikeParameter(
-                '',
+                $param_name,
                 false,
                 $tree_type instanceof Union ? $tree_type : new Union([$tree_type]),
                 null,

src/Psalm/Storage/FunctionLikeParameter.php

@@ -15,6 +15,8 @@ final class FunctionLikeParameter implements HasAttributesInterface, TypeNode
     use UnserializeMemoryUsageSuppressionTrait;
 
     /**
+     * Parameter name, without `$`
+     *
      * @var string
      */
     public $name;

tests/CallableTest.php

@@ -1908,6 +1908,18 @@ function bar($cb_arg) {}
 
                     foo("bar");',
             ],
+            'callableWithNamedArguments' => [
+                'code' => <<<'PHP'
+                <?php
+                /** @param callable(int $i) $c */
+                function f(callable $c): void {
+                    $c(i: 1);
+                }
+                PHP,
+                'assertions' => [],
+                'ignored_issues' => [],
+                'php_version' => '8.0',
+            ],
         ];
     }
 
@@ -2494,6 +2506,18 @@ function int_int_int_int_string(Closure $f): void {}
                 'ignored_issues' => [],
                 'php_version' => '8.0',
             ],
+            'callableWithInvalidNamedArguments' => [
+                'code' => <<<'PHP'
+                <?php
+                /** @param callable(int $a) $c */
+                function f(callable $c): void {
+                    $c(b: 1);
+                }
+                PHP,
+                'error_message' => 'InvalidNamedArgument',
+                'ignored_issues' => [],
+                'php_version' => '8.0',
+            ],
         ];
     }
 }