If I have a function:
function call_me( callable $function ) {}
And I have code to call it like call_me( 'var_dump' ) then the string "var_dump" should add go-to definition / treat it as a first class reference to the function similar to var_dump(...) (first-class callable syntax). Given call_me() has types for callable it seems within reason that intellisense should be able to resolve string and [ $this, 'my_method' ] style callable values to their definitions / rich hover information.
