src/Reflection/ReflectionParameter.php
public function allowsNull() : bool
    {
        if (! $this->hasType()) {
            return true;
        }

        if ($this->node->type instanceof NullableType) {
            return true;
        }

        if (! $this->isDefaultValueAvailable()) {
            return false;
        }

        return $this->getDefaultValue() === null;
    }
public function allowsNull() : bool
    {
        if (! $this->hasType()) {
            return true;
        }

        if ($this->node->type instanceof NullableType) {
            return true;
        }

        if (! $this->isDefaultValueAvailable()) {
            return false;
        }

        return $this->getDefaultValue() === null;
    }
Does this method allow null for a parameter?