Phan\Language\Element\Parameter::setDefaultValueType PHP Method

    public function setDefaultValueType(UnionType $type)
    {
        $this->default_value_type = $type;
    }

 /**
  * @return Parameter
  * A parameter built from a node
  *
  * @see \Phan\Deprecated\Pass1::node_param
  * Formerly `function node_param`
  */
 public static function fromNode(Context $context, CodeBase $code_base, Node $node) : Parameter
 {
     assert($node instanceof Node, "node was not an \\ast\\Node");
     // Get the type of the parameter
     $union_type = UnionType::fromNode($context, $code_base, $node->children['type']);
     // Create the skeleton parameter from what we know so far
     $parameter = new Parameter($context, (string) $node->children['name'], $union_type, $node->flags ?? 0);
     // If there is a default value, store it and its type
     if (($default_node = $node->children['default']) !== null) {
         // We can't figure out default values during the
         // parsing phase, unfortunately
         if (!$default_node instanceof Node || $default_node->kind == \ast\AST_CONST || $default_node->kind == \ast\AST_UNARY_OP || $default_node->kind == \ast\AST_ARRAY) {
             // Get the type of the default
             $union_type = UnionType::fromNode($context, $code_base, $default_node);
             // Set the default value
             $parameter->setDefaultValueType($union_type);
         } else {
             try {
                 // Get the type of the default
                 $union_type = UnionType::fromNode($context, $code_base, $default_node, false);
             } catch (IssueException $exception) {
                 // If we're in the parsing phase and we
                 // depend on a constant that isn't yet
                 // defined, give up and set it to
                 // bool|float|int|string to avoid having
                 // to handle a future type.
                 $union_type = new UnionType([BoolType::instance(), FloatType::instance(), IntType::instance(), StringType::instance()]);
             }
             // Set the default value
             $parameter->setDefaultValueType($union_type);
         }
     }
     return $parameter;
 }