frees-rpc new Generation

[juanpedromoreno]

frees-rpc will adopt the new generation of Scala Macros in the Freestyle ecosystem. This new version of the scala macros will be supported natively by the compiler in 2.13, under the scalac option -Ymacro-annotations, thanks to scala/scala#6606.

However, the migration of the current scalameta macros (no longer under development and won't support 2.13.x) to the new Scala Macros can be huge, mainly taking into account both https://github.com/frees-io/freestyle and https://github.com/frees-io/freestyle-rpc.

As you probably know, frees-rpc is currently depending on frees-core for defining the tagless final algebras, so we are suggesting two steps work to achieve this migration.

1. First, in order to parallelize the work, we need to decouple temporarily frees-rpc from frees-core. The reason would be just to minimize the potential blockers from the migration in frees-core side, which presumably would be bigger, so we could migrate Freestyle RPC faster and independently from the core. As you can imagine, we want frees-core back to frees-rpc as soon as both are inline in terms of binary compatibility (it could be considered the third stage).

2. As part of the second step, we'll do the migration itself, where the RPC @service macro annotation will be migrated to use the new generation of Scala Macros.

The Freestyle Maintainers team hope this makes sense and want to say that any kind of feedback is very welcomed :)

• Related to SPIKE: Replacements for scalameta-based macros frees-io/freestyle#539.

[juanpedromoreno]

Closed by #339