Prior to this commit, an infinite recursion would occur if a
@Configuration class were nested within its superclass, e.g.
abstract class Parent {
@Configuration
static class Child extends Parent { ... }
}
This is because the processing of the nested class automatically
checks the superclass hierarchy for certain reasons, and each
superclass is in turn checked for nested @Configuration classes.
The ConfigurationClassParser implementation now prevents this by
keeping track of known superclasses, i.e. once a superclass has been
processed, it is never again checked for nested classes, etc.
Issue: SPR-8955
08e2669b84