Re: functors with template lambdas

[weaselcat via Digitalmars-d-learn]

On Saturday, 16 May 2015 at 02:04:39 UTC, Vlad Levenfeld wrote:

I think this code should be allowed, but it isn't:

        struct Functor (T)
        {
                T a;

                auto ref fmap (alias f)()
                {
                        return Functor (f(a));
                }
        }

        auto ref identity (T)(auto ref T a)
        {
                return a;
        }

        void main()
        {
                Functor!int a;

                static auto id (T)(T x)
                {return x;}

                a.fmap!identity; // ok

                a.fmap!id; // ok

                a.fmap!((int x) => x); // ok

a.fmap!(x => x); // Error: template instance fmap!((x) => x) cannot use local '__lambda1' as parameter to non-global template fmap(alias f)()

        }

This seems like one of those things that doesn't work because of some compiler implementation detail rather than a consequence of the language rules but I'm not sure. Opinion?

very long standing compiler bug
https://issues.dlang.org/show_bug.cgi?id=3051