I have heard this before but never really understood it.

Take this:

```

int bar(int arg); // May throw

int foo(int arg) {

    int b = bar(arg);

    return b * 5; 

}

```

VS:

```

Error<int> bar(int arg); // Uses error type

Error<int> foo(int arg) {

  auto b = bar(arg);

  if(b.ok()) { // Happy Path

    return b.unwrap() * 5;
  }

  return e; // Exceptional Path

}

```

In the happy case (no exception) how can the first version be harder to optimize than the second one? In the exceptional case exceptions will probably be slower. You trade fast common case for slow exceptional case so it makes sense to me. Is the slower one the one that is hard to optimize? Is this what we are talking about when optimizations are harder to reason about? Or are there some other things that become harder because of exception? Things like RAII, defer, goto stuff?