Generically call a function on Variant's payload?

[Nick Sabalausky (Abscissa)]

On 08/19/2018 10:23 PM, Jonathan M Davis wrote:
> On Sunday, August 19, 2018 6:33:06 PM MDT Nick Sabalausky (Abscissa) via
> Digitalmars-d-learn wrote:
>>
>> Maybe something involving using Variant.coerce to convert the payload to
>> a single common type? Not sure how I would do that though.
> 
> You could always create a wrapper type. Whatever code you're dealing with is
> going to need to statically know what type it's using even that's a base
> type in a class hierarchy. So, you need to present a type which actually has
> the appropriate API even if internally, it can dynamically handle several
> types which have that API, and it's not known ahead of time which type that
> is.
> 

I guess the parts I'm unclear on are:

1. What mechanism does Variant.coerce!SomeType use to attempt conversion 
to SomeType?

2. How (if possible) can I provide a way to convert something to type 
SomeType which Variant.coerce!SomeType will then recognize and use?