Don't allocate a vec for repeat count if it's not used

[coolreader18]

No description provided.

[kevinmehall]

I think we might already be getting the optimization you're trying to make here. If result_used == false is passed to the inner expression, its return type will be () and Rust is smart enough to not actually allocate for that -- Vec<()> is just a counter.

Is there an example where you've confirmed that it's actually allocating and doesn't need to?

[coolreader18]

Ohhh, I think I missed that; you're right. That's clever, generic programming ftw I suppose.