fix negated predicate decorated callable

phpstan-baseline.neon

@@ -108,12 +108,6 @@ parameters:
 			count: 2
 			path: src/Predicate/ConstantPredicate.php
 
-		-
-			message: '#^Expression "\$this\-\>negated" on a separate line does not do anything\.$#'
-			identifier: expr.resultUnused
-			count: 1
-			path: src/Predicate/NegatedPredicate.php
-
 		-
 			message: '#^Method Kadet\\Functional\\Predicate\\NegatedPredicate\:\:__invoke\(\) has parameter \$args with no type specified\.$#'
 			identifier: missingType.parameter

src/Predicate/NegatedPredicate.php

@@ -39,6 +39,6 @@ class NegatedPredicate extends AbstractPredicate implements Decorator
 
     public function getDecorated()
     {
-        $this->negated;
+        return $this->negated;
     }
 }

tests/Collections/LibraryCallablesTest.php

@@ -0,0 +1,40 @@
+<?php
+/**
+ * Copyright 2026 Kacper Donat
+ *
+ * @author Kacper "Kadet" Donat <kacper@kadet.net>
+ *
+ * Full license available in separate LICENSE file
+ */
+
+use Kadet\Functional as f;
+use Kadet\Functional\Collections as c;
+use Kadet\Functional\Predicates as p;
+
+/**
+ * The library's own callables (predicates, pipes, decorators) used as collection callbacks.
+ */
+class LibraryCallablesTest extends \PHPUnit\Framework\TestCase
+{
+    // negated predicates
+
+    public function testFilterWithNegatedInternalFunction()
+    {
+        $this->assertSame([1 => 'x'], c\filter(f\not(is_numeric(...)))(['1', 'x']));
+    }
+
+    public function testFilterWithNegatedClosure()
+    {
+        $this->assertSame([1], c\filter(f\not(fn ($x) => $x > 1))([1, 2]));
+    }
+
+    public function testFilterWithNegatedPredicateMethod()
+    {
+        $this->assertSame([1], c\filter(p\gt(1)->not())([1, 2]));
+    }
+
+    public function testRejectWithNegatedPredicate()
+    {
+        $this->assertSame([1 => 2], c\reject(p\gt(1)->not())([1, 2]));
+    }
+}