+ # Is the type a `MErrorType` or contains an `MErrorType`?
+ #
+ # `MErrorType` are used in result with conflict or inconsistencies.
+ #
+ # See `is_legal_in` to check conformity with generic bounds.
+ fun is_ok: Bool do return true
+
+ # Is the type legal in a given `mmodule` (with an optional `anchor`)?
+ #
+ # A type is valid if:
+ #
+ # * it does not contain a `MErrorType` (see `is_ok`).
+ # * its generic formal arguments are within their bounds.
+ fun is_legal_in(mmodule: MModule, anchor: nullable MClassType): Bool do return is_ok
+