I've come across an issue when trying to use Exact. I've got a hierarchy of types, and i'm also trying to implement classes based on those types. Here's the example (also here's the playground link https://tsplay.dev/w8xKdw) that is about as small as I can make it.

type SmallType = {
  one: string;
}

type IntermediateType = {
  inter_a?: SmallType;
}

type FinalType = {
  final_a?: IntermediateType;
}

class SmallClass implements Exact<SmallType, SmallClass> {
  one: string;

  constructor(one: string){
    this.one = one;
  }
}

class IntermediateClass implements Exact<IntermediateType, IntermediateClass> {
  inter_a?: SmallClass;
}

class FinalClass implements Exact<FinalType, FinalClass> {
  final_a?: IntermediateClass; // <-- this field generates a typescript error
}

The bug is right there with FinalClass. If I use exact, I get a type error:

Property 'final_a' in type 'FinalClass' is not assignable to the same property in base type 'ExactObject<FinalType, FinalClass>'.
  Type 'IntermediateClass | undefined' is not assignable to type 'ExactObject<IntermediateType, IntermediateClass | undefined> | undefined'.
    Type 'IntermediateClass' is not assignable to type 'ExactObject<IntermediateType, IntermediateClass | undefined>'.
      Type 'IntermediateClass' is not assignable to type '{ inter_a?: ExactObject<SmallType, never> | undefined; }'.
        Types of property 'inter_a' are incompatible.
          Type 'SmallClass | undefined' is not assignable to type 'ExactObject<SmallType, never> | undefined'.
            Type 'SmallClass' is not assignable to type 'ExactObject<SmallType, never>'.
              Type 'SmallClass' is not assignable to type 'Record<string | number | symbol, never>'.
                Index signature for type 'string' is missing in type 'SmallClass'.

Should I be able to use Exact like this? Some of the types are coming from a code generator, so that's why i'm trying to make sure my classes match.