public MutationSignature alsoMutatesArg(int n) {
    if (myParameters.length > n && myParameters[n]) return this;
    boolean[] params = Arrays.copyOf(myParameters, Math.max(n + 1, myParameters.length));
    params[n] = true;
    return new MutationSignature(myThis, myIo, params);
  }
public MutationSignature alsoMutatesArg(int n)