Type Hint private variables

Using PHPStorm 9.0.1.

I'm having an issue which works but I get  a warning messasge. Here is an example class that give the warning:

<?php
    include_once "rw.fielddefs.class.php";
    class TTest {
        private $FieldDefs;
        public function __construct()
        {
            $this->FieldDefs = new TFieldDefs();
            // load some info into FieldDefs.
        }
        public function GetFieldValue($aColumnName)
        {
            return $this->FieldDefs->Value($aColumnName); // I am getting a warning: Method 'Value' not found in class, however this does work.
        }
    }

However, if I do the funciton this way I get not error:

public function GetFieldValuie(TFieldDefs $aFieldDefs, $aColumnName)
{
    return $aFieldDefs->Value($aColumnName); // No warning message but I have to pass the class as a parameter.
}

Is there a way to Type Hint a variable, for example:

private TFieldDefs $FieldDefs;

Using this method gives me an error, but this is an example only.

Regards,
Rich