member function as template parameter workaround needed

[bearophile]

timotheecour:

>         //attempt#2
>         //also tried to just pass x=>a.fun2(x), but then 
> ParameterTypeTuple doesn't work with lambdas.

I think "x => a.fun2(x)" isn't an anonymous function, it's 
templated.

Bye,
bearophile