Load subclasses from global classes

[fabiopagoti]

Simple inheritance

Given
Class CL_SUB is a subclass of CL_SUPER

When
CL_SUPER is loaded

Then
New attribute 'subclasses' should be loaded with this information

Multiple inheritance

Given
Class CL_SUB is a subclass of CL_SUPER AND
Class CL_SUB_SUB is a subclass of CL_SUB.

When
CL_SUPER is loaded

Then
New attribute 'subclasses' should be loaded with this information.
There should be an indirect link between CL_SUPER and CL_SUB_SUB (via CL_SUB)