passindro

struct Fn{A, B}
    f :: Function
end

function (f::Fn{A, B})(a :: A) :: B where {A, B}
    f.f(a)
end

abstract type Sig end

passindro

function emmmm(expr, guard)
    @match expr begin
       :(function $_(a, b, $(_...), $last)
           $(block...) end) 
        where guard(last) => (last, block)
    end
end

head = x->x[1]