Add TryMap (Runtime Target Type)

[randellhodges]

Just like the existing map that can be generated:
https://mapperly.riok.app/docs/configuration/generic-mapping/#runtime-target-type-parameter

Add ability to generate a TryMap, something like:

public static partial bool TryMap(object source, Type targetType, out object result);

Why?
I'm playing around with replacing Automapper and we use DI and IMapper everywhere. I can't quickly just remove that, so I started using the ideas here, which is mostly working for me:
#397 (comment)

Inside the MapperlyMapperAsAutomapper there is just a single private MapperlyMapper _mapper = new();

Ideally, I'd use DI to inject X number of map classes and then I can try do a TryMap call on each of them until I get a result. These would be discovered when setting up the DI container and some of them could be inside various assemblies.

I would probably cache which instance resolved my map so that next time I can just look that up and not have to loop thru everything, but that is an optimization on my side.

[latonz]

Thanks for the suggestion. Since Mapperly is source-generated (all mappings need to be known at compile-time), a TryMap approach doesn’t fit well with the design and use cases we target, and this scenario seems like an edge case rather than a common need. Adding it would introduce significant complexity to Mapperly, which we want to avoid in order to keep the library maintainable. Therefore, we don’t plan to implement a TryMap method.

[randellhodges]

Ok. I didn't really see it as much different than the existing runtime Map pattern that generates a big switch expression, just changing it to a switch statement and not throwing an Exception. I did submit a working PR and I do see how implementing the out parameter does indeed permeate thru the library.

I had sort of decided against a pseudo DI pattern and just take the time to rip out all traces of the automapper way and go to a static mapperly class anyway, so it isn't a big deal anyway.