T[new]

[Walter Bright]

Brad Roberts wrote:
> Yay.  What will happen with slices over a T[new] when the underlying T[new] must
> be moved due to resizing?  The behavior needs to be at least well specified, if
> not well defined.

Great question! It's no different from what happens with any container 
when its contents change and there are references to the old content.

What won't happen is the slice won't be pointing to unallocated memory, 
thanks to the gc. Resizing the T[new] will not cause the old contents to 
be deleted.

The slice will either point to the old content, if the resize caused a 
move, or the new content, if it was resized in place. So it will still 
be implementation-defined behavior.

But the likelihood of getting caught by such behavior is much less 
likely with T[new], as one can clearly see in the code where the 
resizeables are, rather than the current situation where any slice could 
be resized by anyone.

I think that taking a slice of a T[new], then resizing the T[new], will 
be rare (or at least should be). Normally, a T[new] will be built, and 
when it is all done, it is converted to a T[] and there is no longer any 
way to resize it.