In the class file format, many values are u1 and u2, which are consistently represented in the Class-File API as int. However, such representation omitted that the actual values have a more narrow range, and performs no value restriction when users create API models via factories.

Since for these values, almost all usages of unrepresentable values indicate a user error, I propose to eagerly check for them and throw IllegalArgumentException. For some common aliases, such as using -1 for "all bits set" class file minor version, we can have exceptions.

Note that some values are illegal but representable - this proposal does not intend to restrict those values.