[Issue 15685] &slice[$] should be allowed

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=15685

Mathias LANG <pro.mathias.lang at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |pro.mathias.lang at gmail.com
         Resolution|---                         |INVALID

--- Comment #1 from Mathias LANG <pro.mathias.lang at gmail.com> ---
In order to get this address, you should do `slice.ptr + slice.length`.
`&slice[$]` would give you an element *after* the array, so it's potentially
pointing to unallocated / invalid / protected memory. It's a pointer you should
*never* access.
When writing C-style code, it's common to do `while (p++ < pend)` where `pend`
is this pointer, but the type system can't guarantee you'll use it correctly.

Also, that would break `@safe` code. So marking as `INVALID` since we don't
want to allow it, and there's an easy workaround: use `ptr + length`.

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