Huh, I didn't know about `return` in `defer`, but is it really useful?

No, I actually misremembered… you can’t return in a defer.

The magical thing I was misremembering is that you can reference a not-yet-defined value in a defer, so long as all code paths define it once:

  fn callFoo() -> FooResult {
    let fooParam: Int // declared, not defined yet
    defer {
      // fooParam must get defined by the end of the function
      foo(fooParam)
      otherStuffAfterFoo() // …
    }

    // all code paths must assign fooParam
    if cond {
      fooParam = 0
    } else {
      fooParam = 1
      return // early return!
    }

    doOtherStuff()
  }