A memoized lookup of an enclosing non local class.

Let's consider an example of an owner chain:

pkg1 <- pkg2 <- class A <- object B <- class C <- def foo <- class Foo <- class Bar

For an object, we work with its moduleClass so we can refer to everything as classes.

Classes A, B, C are non local so they are mapped to themselves. Classes Foo and Bar are local because they are defined within method foo.

Let's define non local class more precisely. A non local class is a class that is owned by either a package or another non local class. This gives rise to a recursive definition of a non local class that is used in the implementation of the mapping.

Thanks to memoization, the amortized cost of a lookup is O(1). We amortize over lookups of all class symbols in the current compilation run.

Additionally, you can query whether a given class is local. Check isLocal's documentation.