Shouldn't invalid references like this fail at compile time?

[Jonathan M Davis]

On Wednesday, January 24, 2018 18:46:38 Walter Bright via Digitalmars-d 
wrote:
> On 1/23/2018 7:22 PM, Jonathan M Davis wrote:
> > We need to do that anyway for the overly large
> > objects (and unfortunately don't last I heard).
>
> I put a limit in at one time for struct/class sizes to prevent this issue,
> but got a lot of pushback on it and it was reverted.
>
> Perhaps we can revisit that - and have large struct/classes be allow only
> in non- at safe code.
>
> In general, though, if you don't have struct/class object sizes larger
> than the protected memory at null, you're safe with null dereferences.

Yes, but we need to do _something_ about the overly large structs/classes if
we want @safe to be bulletproof like it's supposed to be (barring misuse of
@trusted, of course). I'd be inclined towards adding extra null-checks in
those cases just because you'd end up with a balooning of @system code in
your code if we made dereferencing pointers/references to them @system, but
regardless, the important thing is that we do something with them (whatever
that may be) so that we don't have code that the compiler claims to be @safe
and then goes and does something naughty with memory. Right now, those types
are a lot like dynamic arrays with -noboundscheck except that the programmer
didn't knowingly choose to be unsafe.

Personally, I doubt that I've ever written code with types that large, but I
really have no idea, because I don't know what the boundary is. I just know
that I don't usually have really large types. But right now, it probably
wouldn't be all that hard to shoot yourself in the foot by having a
particularly large static array, and most folks would probably have no idea
that they were making it so that they wouldn't get segfaults on null. The
only reason that I know that that's possible is because of previous
discussions on the topic here in the newsgroup, and I'm sure that plenty of
other folks are in the same boat except that they haven't read those
discussions and so still have no clue about it.

- Jonathan M Davis