how to compose delegate type

[Ellery Newcomer]

On Sunday, 8 December 2013 at 00:43:51 UTC, Jesse Phillips wrote:
>
> What is wrong with the current template which returns an 
> immutable delegate type? It still store you're immutable member 
> function.

It composes the wrong type. It composes a type that has different 
constness than the target type, which will likely cause problems 
due to transitive const.

Anyways, I'm trying to find a workaround to

https://d.puremagic.com/issues/show_bug.cgi?id=11694