Description:
------------
The documentation does not say that interfaces can be extended, see the example code below for an example.

An error is being throwed because the secondary interface declares baz()

Reproduce code:
---------------
interface a
{
	public function foo();
}

interface b extends a
{
	public function baz(Baz $baz);
}

class c implements b
{
	public function foo()
	{
	}

	public function baz(Foo $foo)
	{
	}
}