Runtime error trying to call opCall on variant array of objects

[aliak via Digitalmars-d-learn]

Hey, so I'm trying to make an variant array of objects (each one 
has an opCall defined) and then call each of them in succession. 
It doesn't seem to be working. The error I get is:

"Cannot apply `()' to a value of type `Command!(__lambda1, int)". 
I think it's failing when it checks for "!isFunctionPointer!A && 
!isDelegate!A".

Here's the bit of code:

struct Command(alias fun, Args...) {
    Args args;
    this(Args args) {
        args = args;
    }
    auto opCall() {
        return fun(args);
    }
}

auto command(alias fun, Args...)(Args args) {
    return Command!(fun, Args)(args);
}

void main() {
    auto commands = variantArray(
        command!(a => a + 1)(1),
        command!(a => a + 2)(1),
        command!(a => a + 3)(1),
    );

   // commands.each!(a => a()); // <-- crashes runtime

    typeid(commands[0]).writeln; // 
std.variant.VariantN!32LU.VariantN

    auto cmd = command!(a => a + 1)(1);
    typeid(cmd).writeln; // scratchpad.main.Command!(__lambda4, 
int).Command
}

Is there a way to do what I'm trying to do?

Cheers!