mixed ReflectionNamedType does allow null values

src/Reflection/Adapter/ReflectionNamedType.php

@@ -7,6 +7,8 @@
 use ReflectionNamedType as CoreReflectionNamedType;
 use Roave\BetterReflection\Reflection\ReflectionNamedType as BetterReflectionNamedType;
 
+use function strtolower;
+
 /**
  * @psalm-suppress MissingImmutableAnnotation
  */
@@ -23,7 +25,7 @@ public function getName(): string
 
     public function __toString(): string
     {
-        return ($this->allowsNull ? '?' : '')
+        return ($this->allowsNull && strtolower($this->betterReflectionType->getName()) !== 'mixed' ? '?' : '')
             . $this->betterReflectionType->__toString();
     }
 

src/Reflection/Adapter/ReflectionType.php

@@ -43,6 +43,6 @@ public static function fromTypeOrNull(BetterReflectionNamedType|BetterReflection
             return new ReflectionIntersectionType($betterReflectionType);
         }
 
-        return new ReflectionNamedType($betterReflectionType, false);
+        return new ReflectionNamedType($betterReflectionType, $betterReflectionType->allowsNull());
     }
 }

src/Reflection/ReflectionNamedType.php

@@ -103,7 +103,7 @@ public function getClass(): ReflectionClass
 
     public function allowsNull(): bool
     {
-        return false;
+        return strtolower($this->name) === 'mixed';
     }
 
     public function __toString(): string

test/unit/Reflection/Adapter/ReflectionTypeTest.php

@@ -4,16 +4,21 @@
 
 namespace Roave\BetterReflectionTest\Reflection\Adapter;
 
+use PhpParser\Node\Identifier;
 use PHPUnit\Framework\TestCase;
 use ReflectionClass as CoreReflectionClass;
 use ReflectionType as CoreReflectionType;
 use Roave\BetterReflection\Reflection\Adapter\ReflectionIntersectionType as ReflectionIntersectionTypeAdapter;
 use Roave\BetterReflection\Reflection\Adapter\ReflectionNamedType as ReflectionNamedTypeAdapter;
+use Roave\BetterReflection\Reflection\Adapter\ReflectionType;
 use Roave\BetterReflection\Reflection\Adapter\ReflectionType as ReflectionTypeAdapter;
 use Roave\BetterReflection\Reflection\Adapter\ReflectionUnionType as ReflectionUnionTypeAdapter;
 use Roave\BetterReflection\Reflection\ReflectionIntersectionType as BetterReflectionIntersectionType;
+use Roave\BetterReflection\Reflection\ReflectionNamedType;
 use Roave\BetterReflection\Reflection\ReflectionNamedType as BetterReflectionNamedType;
+use Roave\BetterReflection\Reflection\ReflectionParameter;
 use Roave\BetterReflection\Reflection\ReflectionUnionType as BetterReflectionUnionType;
+use Roave\BetterReflection\Reflector\Reflector;
 
 use function array_combine;
 use function array_map;
@@ -83,4 +88,14 @@ public function testFromTypeOrNullWithIntersectionType(): void
     {
         self::assertInstanceOf(ReflectionIntersectionTypeAdapter::class, ReflectionTypeAdapter::fromTypeOrNull($this->createMock(BetterReflectionIntersectionType::class)));
     }
+
+    public function testMixedAllowsNull(): void
+    {
+        $type = ReflectionType::fromTypeOrNull(new ReflectionNamedType(
+            $this->createMock(Reflector::class),
+            $this->createMock(ReflectionParameter::class),
+            new Identifier('mixed'),
+        ));
+        self::assertTrue($type->allowsNull());
+    }
 }

test/unit/Reflection/ReflectionNamedTypeTest.php

@@ -51,6 +51,12 @@ public function testAllowsNull(): void
         self::assertFalse($noNullType->allowsNull());
     }
 
+    public function testMixedAllowsNull(): void
+    {
+        $noNullType = $this->createType('mixed');
+        self::assertTrue($noNullType->allowsNull());
+    }
+
     public function isBuildinProvider(): Generator
     {
         yield ['string'];