Call site 'ref'

[Mail Mantis]

2012/1/15 Alex Rønne Petersen <xtzgzorex at gmail.com>:
> Hi,
>
> I don't know how many times I've made the mistake of passing a local
> variable to a function which takes a 'ref' parameter. Suddenly, local
> variables/fields are just mutating out of nowhere, because it's not at all
> obvious that a function you're calling is taking a 'ref' parameter. This is
> particularly true for std.utf.decode().
>
> Yes, I realize I could look at the function declaration. Yes, I could read
> the docs too. But that doesn't prevent me from forgetting that a function
> takes a 'ref' parameter, and then doing the mistake again. The damage is
> done, and the time is wasted.
>
> I think D should allow 'ref' on call sites to prevent these mistakes. For
> example:
>
> string str = ...;
> size_t pos;
> auto chr = std.utf.decode(str, ref pos);
>
> Now it's much more obvious that the parameter is passed by reference and is
> going to be mutated.
>
> Ideally, this would not be optional, but rather *required*, but I realize
> that such a change would break a *lot* of code, so that's probably not a
> good idea.
>
> Thoughts?
>
> --
> - Alex

I don't see how call cite ref will help the issue. If you don't read
ddoc, how will you know what exactly function does with it's ref
parameter - statistically? Knowing that function takes parameter by
ref doesn't help understanding it's logic. Also, knowing that function
doesn't take any ref parameters doesn't mean you don't need to read
it's documentation.