What is this strange alias syntax?

[Stewart Gordon]

On 22/05/2011 21:51, Timon Gehr wrote:
<snip>
>> I suspect what Andrej actually meant is to kill treating function
>> signatures as types in this way.  And possibly "enhancement
>> request" rather than "bug".
>
> It is the opposite of an enhancement request.  It means removing a
> feature that cannot be meaningfully substituted by other features.

Unless you know a use case I've never heard of, it's no more "a feature that cannot be 
meaningfully substituted by other features" than the C preprocessor.

> (also, removing it increases the inconsistency of the language and
> makes the compiler more complex).

I disagree.  My point is that function types and data types have practically nothing in 
common.  So your argument seems to me like claiming that D is inconsistent because classes 
and functions aren't interchangeable.

<snip>
>> True, if you use "type" in a broad sense.  But it doesn't declare
>> a variable of that type, and you can't use it as a type as such.
>> Really, function signatures and data types are distinct entities
>> and ought not to be interchangeable.
>
> You can alias any symbol.  Data types and other symbols are
> distinct entities too.  By your arguments, this is a bad thing to
> have.

But do function signatures count as symbols?  I'm not sure.

> Also, a function signature, while not a data type is still a _type_
> (the "broad sense" is the D sense.  You can do
> typeof(some_function)).

And do what _with_ it, let alone that cannot be done by any other means?

<snip>
> alias int func();
>
> int main(){
>      static assert(is(typeof(main)==func);

alias int function() func;
static assert (is(typeof(&main) == func));

>      return 0;
> }
>
> I do not get why anybody would want to remove the possibility to
> refer to function signatures.  It can be handy for template
> constraining.
<snip>

Can you give an example?

Stewart.