Consider adding a support for duplicated interfaces in the "implements" chain

[quasilyte]

This code won't compile with KPHP:

interface Node {}
interface FunctionLike extends Node {}

class Expr implements Node {}
class ArrowFunc extends Expr implements FunctionLike {}

https://github.com/nikic/PHP-Parser/blob/4848a0d734833003eebc969ab395f36b44419f85/lib/PhpParser/Node/Expr/ArrowFunction.php

Error message:

duplicated class: PhpParser\Node in hierarchy from class: PhpParser\Node\Expr\ArrowFunction

I haven't done any investigations yet; just reporting an obstacle I faced. :)