This seems like a really roundabout formulation. `variadicFunctionStyle!T` is known at compile-time, so the runtime variable `requiredArgs` and the runtime `if`-statement is misleading.

A more proper formulation would probably be:
```d
static if(variadicFunctionStyle!T == Variadic.no)
    enum requiredArgs = Args.length + 1;
else
    enum requiredArgs = Args.length;
```