Type Parameters on Scala Macro Annotations

Question

I\'m trying to use macro annotations in scala, where my macro annotation would take an argument of another type. It would then use scala reflection to look at the passed in

Answer 1

In macro paradise 2.0.0-SNAPSHOT we have quite a tricky way of accessing type parameters for macro annotations (the situation will improve later on when we have dedicated APIs for that, but right now it's very difficult to introduce new functionality to scala-reflect.jar in macro paradise, so the current API is a bit rough).

For now it's necessary to specify the type parameter on the annotation class and not to declare any type parameters on the macroTransform method. Then, in macro expansion, access c.macroApplication and extract the untyped tree corresponding to the passed type parameter. Afterwards, do c.typeCheck as described in Can't access Parent's Members while dealing with Macro Annotations.