On Sunday, 4 December 2022 14:40:25 PST Frederick Virchanza Gotham via Std-
Proposals wrote:
> Is there some how some way that we can allow 'if constexpr' inside a
> fold expression? I know that we can have a fold expression containing
> a lambda (and that the lambda can contain 'if constexpr'), but in this
> example we need 'if constexpr' by itself.

Not the if, but the requires can be in a constant expression (I think)

    if constexpr ((requires{ get<Types>(p)->Method(a); } || ...))
        return tailcall(a...);

You can probably simply solve your problem by writing a recursive function
instead.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel DCAI Cloud Engineering