# A kind of class.
#
#  * `abstract_kind`
#  * `concrete_kind`
#  * `interface_kind`
#  * `enum_kind`
#  * `extern_kind`
#
# Note this class is basically an enum.
# FIXME: use a real enum once user-defined enums are available
class MClassKind
	redef var to_s

	# Can a class of kind `self` define a membership predicate?
	var can_customize_isa: Bool

	# Can a class of kind `self` define a constructor?
	var can_init: Bool

	# Is a constructor required?
	var need_init: Bool

	# TODO: private init because enumeration.

	# Can a class of kind `self` specializes a class of kind `other`?
	fun can_specialize(other: MClassKind): Bool
	do
		if other == interface_kind then
			# everybody can specialize interfaces
			return true
		else if self == interface_kind or self == enum_kind then
			# no other case for interfaces and enums
			return false
		else if self == subset_kind then
			# A subset may specialize anything, except another subset.
			# TODO: Allow sub-subsets once we can handle them.
			return other != subset_kind
		else if self == extern_kind then
			# only compatible with themselves
			return self == other
		else
			# assert self == abstract_kind or self == concrete_kind
			return other == abstract_kind or other == concrete_kind
		end
	end
end