static Type resolveTypeVariable(Type context, Class<?> contextRawType, TypeVariable<?> unknown) {
    Class<?> declaredByRaw = declaringClassOf(unknown);

    // we can't reduce this further
    if (declaredByRaw == null) {
      return unknown;
    }

    Type declaredBy = getGenericSupertype(context, contextRawType, declaredByRaw);
    if (declaredBy instanceof ParameterizedType) {
      int index = indexOf(declaredByRaw.getTypeParameters(), unknown);
      return ((ParameterizedType) declaredBy).getActualTypeArguments()[index];
    }

    return unknown;
  }