On Sat, 21 Apr 2012 15:46:29 -0400, Mehrdad <[email protected]> wrote:
alias int delegate(out ItemGetter next) ItemGetter;
We currently can't do the above^ in D, but what do people think about
allowing it?
i.e. More specifically, I think an alias expression should be able to
refer to the identifier (unless it doesn't make sense, like including a
struct inside itself).
(It would require a look-ahead.)
It doesn't work.
If I do this:
alias int delegate() dtype;
alias int delegate(dtype d) ddtype;
pragma(msg, ddtype.stringof);
I get:
int delegate(int delegate() d)
Note how it's not:
int delegate(dtype d)
Why? Because alias does not create a new type. It's a new symbol that
*links* to the defined type.
How shall the compiler expand your example so it can know the type? It
works for classes because classes are a new type which do not need to have
another type backing it.
The solution? Well, there are two possible ones. One is you create a
ficticious type (or use void *) and cast when inside the delegate. The
other is to not use delegates, but use types instead. Either a struct or
a class/interface will do, something for the compiler to anchor on.
-Steve
