std.sumtype?

[Paul Backus]

On Monday, 22 March 2021 at 19:24:54 UTC, JN wrote:
> Does anyone know if it would be possible to make it support (it 
> doesn't support it now) this kind of syntax:
>
> Temperature t1 = Fahrenheit(98.6);
> isFahrenheit(t1); // works
> isFahrenheit(Fahrenheit(98.6)); // doesn't work :(

You can do this by adding an additional overload to isFahrenheit:

bool isFahrenheit(T)(T t)
     if (staticIndexOf!(T, Temperature.Types) >= 0)
{
     return is(T == Fahrenheit);
}

bool isFahrenheit(Temperature temp)
{
     // Forward to template overload
     return temp.match!isFahrenheit;
}