Why does scope(success) have to use exceptions?

[Andrej Mitrovic]

On 1/17/13, Era Scarecrow <rtcvb32 at yahoo.com> wrote:
> Obviously your code won't throw, however that's now how scope
> works. Only asserts or exceptions would/can manage to decide if the
> block was successful or not.

That's true for scope exit and scope failure, which need a
try/catch/finally. But if an exception is thrown the stack will
unwind, therefore the next statements won't be run, which is
interesting for scope(success).

Let's look at it this way:

void foo()
{
    int x;
    scope(success)
    {
        x = 1;
    }
    // < code which might throw >
    x = 2;
}

try/catch version:

void foo()
{
    int x;
    try
    {
        x = 2;
        // < code which might throw >
        x = 1;
    }
    catch (Throwable e)
    {
        throw e;
    }
}

But there's no need for a try/catch, you can rewrite this to:

void foo()
{
    int x;
    x = 2;
    // < code which might throw >
    x = 1;  // if there's no stack unwind, this gets executed, hence
scope(success)
}