delegate issue

[via Digitalmars-d-learn]

On Monday, 2 June 2014 at 06:56:54 UTC, captaindet wrote:
> hi,
>
> i stumbled upon something weird - it looks like a bug to me but 
> maybe it is a "feature" that is unclear to me.
>
> so i know i can declare function and delegate pointers at 
> module level.
> for function pointers, i can initialize with a lambda.
> BUT for delegates i get an error - see below
>
> i found out that using module static this(){...} provides a 
> workaround, but why is this necessary?
>
> also, if there is a good reason after all then the error 
> message should make more sense.
>
> /det
>
> ps: i know there is a shorthand syntax for this.
>
> ----
> module demo;
>
> int function(int) fn = function int(int){ return 42; };
> // ok
>
> int delegate(int) dg = delegate int(int){ return 666; };
> // demo.d(6): Error: non-constant nested delegate literal 
> expression __dgliteral6
>
> void main(){}

This doesn't work, because a delegate needs a context it can 
capture, which is available only inside of a function.

The workaround is either, as Mr Smith suggests, to use a static 
constructor, or you can use std.functional.toDelegate() 
(probably, didn't test).