Using delegates in callbacks for extern(C) functions

[Timon Gehr]

On 02/24/2012 07:22 PM, simendsjo wrote:
> I have a C function taking a callback function as a parameter. My
> thought was to wrap this up using a template, but I cannot get it to work:
>
> extern(C) alias void function() Callback;
>
> template Wrap(alias dg)
> {
> extern(C) void Wrap()
> {
> dg();
> }
> }
>
> void main()
> {
> Callback cb = &Wrap!( () {} );
> }
>
> Error: cannot implicitly convert expression (&Wrap) of type void
> delegate() pure nothrow @safe to extern (C) void function()

This is a bug. '() {}' should be inferred as void function()pure nothrow 
@safe. Workaround: The code compiles if you use function() {} instead. I 
don't know if a bug report exists already.