[DX] Early check nullable any type on Filter

Author: samsonasik

src/Assert/Filter.php

@@ -61,17 +61,17 @@ public static function boolean(callable $filter): void
 
         $returnTypeName = $returnType->getName();
 
-        if ($returnTypeName !== 'bool') {
+        if ($returnType->allowsNull()) {
             throw new InvalidArgumentException(sprintf(
                 self::MESSAGE,
-                $returnTypeName
+                '?' . $returnTypeName
             ));
         }
 
-        if ($returnType->allowsNull()) {
+        if ($returnTypeName !== 'bool') {
             throw new InvalidArgumentException(sprintf(
                 self::MESSAGE,
-                '?' . $returnTypeName
+                $returnTypeName
             ));
         }
     }

tests/FilterTest.php

@@ -85,6 +85,22 @@ public function __invoke(int $datum): ?bool
         AtLeast::once($data, $filter);
     }
 
+    public function testWithNullableReturnNonBoolTypeCallable(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        $this->expectExceptionMessage('Expected a bool return type on callable filter, ?string given');
+
+        $data   = [1, 2, 3];
+        $filter = new class {
+            public function __invoke(int $datum): ?string
+            {
+                return 'test';
+            }
+        };
+
+        AtLeast::once($data, $filter);
+    }
+
     public function testWithUnionReturnTypeCallable(): void
     {
         $this->expectException(InvalidArgumentException::class);