Inherit classes defined in variables.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>
Raise upon inheriting a non constant.

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>
Properly inherit data when creating sclass objects

Signed-off-by: Yorick Peterse <yorickpeterse@gmail.com>