Dtype_dispatch: a macro that defines macros that define enums and match them

[mwlon]

https://graphallthethings.com/posts/dtype-dispatch

[artemonster]

this is an obvious case of battling the type system that just gets in the way. The "before" version obviously sucks, but the "after" with magic sprinkled in - sucks even more! is there an alternative solution?

[smusamashah → artemonster]

I dont understand what's going on but it looks like a hack to avoid code duplication. We should be OK with duplication sometimes because it's more explicit and straightforward to mingle and debug.