Is the receiver self?

If "for_self", virtual types of the signature are kept If "not_for_self", virtual type are erased

Property definitions

nitc $ CallSite :: recv_is_self
	# Is the receiver self?
	# If "for_self", virtual types of the signature are kept
	# If "not_for_self", virtual type are erased
	var recv_is_self: Bool
src/semantize/typing.nit:789,2--792,23