e loop and how to widen it.
      Given that the constructor is going to be a default constructor,
      a nice 95% solution might be to execute exactly one constructor and
      then default-bind the resulting LazyCompoundVal to the whole array;
      it'll work whenever the default constructor doesn't touch global state
      but only initializes the object to various default values.
      But if, say, we're making an array of strings,
      depending on the implementation you might have to allocate a new