Issue Description:

I have a Swift class "CoreStoreManagedObject" which subclasses NSManagedObject. More subclasses of this type are created with "objc_allocateClassPair()", and then some NSObject methods are overrided dynamically using "class_addMethod()", in my particular case, "keyPathsForValuesAffectingValueForKey:".

Until Swift 4.1,

type(of: object).keyPathsForValuesAffectingValueForKey("someKeyPath")

always worked as expected, returning values funneled through the created subclasses. In Swift 4.2, "type(of🙂" seems to return the compile-time class (which returns nothing). I am not sure if this is by design or if I hit a rare edge case.

For now I work around this by writing

func cs_dynamicType<T: AnyObject>(of instance: T) -> T.Type {
    
    return object_getClass(instance) as! T.Type
}

and using it in place of "type(of🙂"

I reproduced this with the Unit tests in the library https://github.com/JohnEstropia/CoreStore

Commit: 40f458a09c0177d15ceab1561acaede2799c4f2d (post-fix)

Replace "cs_dynamicType(of🙂" usage in "DynamicModelTests.swift" back to "type(of🙂" to reproduce Unit Test failure.