Support nullable class type hints (#182)

Dice.php

@@ -237,7 +237,12 @@ private function getParams(\ReflectionMethod $method, array $rule) {
 				}
 				// When nothing from $args or $share matches but a class is type hinted, create an instance to use, using a substitution if set
 				else if ($class)	try {
-					$parameters[] = $sub ? $this->expand($rule['substitutions'][$class], $share, true) : $this->create($class, [], $share);
+					if ($sub) {
+						$parameters[] = $this->expand($rule['substitutions'][$class], $share, true);
+					}
+					else {
+						$parameters[] = !$param->allowsNull() ? $this->create($class, [], $share) : null;
+					}
 				}
 				catch (\InvalidArgumentException $e) {
 				}

tests/ConstructParamsTest.php

@@ -132,4 +132,10 @@ public function testNullScalarNested() {
 		$this->assertEquals(null, $obj->nullScalar->string);
 	}
 
+	public function testNullableClassTypeHint() {
+		$nullableClassTypeHint = $this->dice->create('NullableClassTypeHint');
+
+		$this->assertEquals(null, $nullableClassTypeHint->obj);
+	}
+
 }

tests/TestData/ConstructParams.php

@@ -90,3 +90,11 @@ public function __construct($a = null, NB $b = null, NC $c = null) {
 	}
 }
 
+
+class NullableClassTypeHint {
+	public $obj;
+
+	public function __construct(?D $obj) {
+		$this->obj = $obj;
+	}
+}