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February 11, 2013
Re: DIP25 draft available for destruction
On Wednesday, February 06, 2013 02:38:17 Andrei Alexandrescu wrote:
> Probably it'll need a fair amount of tweaking. Anyhow it's in
> destroyable form.
> 
> http://wiki.dlang.org/DIP25

Overall, the ref part seems good, but I'm highly skeptical of the part on 
addresses.

The main point I'd raise about the ref portion is that module-level variables 
need to be grouped in with the static variables. You seem to have marked some 
module-level variables as scope in the examples, but static has no effect on 
module-level variables.

As for the addresses, it seems very bizarre to create a function for doing 
what & does and then make & legal only in very restricted circumstances. 
Having a safeAddressOf for some set of restricted circumstances might make 
sense, but couldn't the compiler just detect that & was safe under those 
circumstances? If the compiler can determine that it's @safe using the 
function, it should be possible for it to determine it without. And 
disallowing & even in @system code is _way_ overkill. The compiler is already 
able to detect at least some unsafe cases (e.g. taking the address of a local 
variable), and it's incredibly common to need to do some of those when 
interacting with C code (e.g. taking the address of a local variable and 
passing it to a C function).

If the problem is ambiguities between taking the address of a function and the 
address of its return value, then I'd think that it would be much cleaner to 
just create a __trait for getting the address of a function. It's needed far 
less than taking the address of a variable, and the difference between & and 
addressOf is just going to sow confusion. It definitely seems like overkill to 
me to introduce a function for doing what & already does just to deal with the 
difference between taking the address of a function and taking the address of 
its return value.

So, I'm in favor of the changes to ref, but I definitely don't like what this
DIP does with &.

- Jonathan M Davis
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