Scala Language Macros Macro Annotation
Example
This simple macro annotation outputs the annotated item as-is.
import scala.annotation.{compileTimeOnly, StaticAnnotation}
import scala.reflect.macros.whitebox.Context
@compileTimeOnly("enable macro paradise to expand macro annotations")
class noop extends StaticAnnotation {
def macroTransform(annottees: Any*): Any = macro linkMacro.impl
}
object linkMacro {
def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
import c.universe._
c.Expr[Any](q"{..$annottees}")
}
}
The @compileTimeOnly annotation generates an error with a message indicating that the paradise compiler plugin must be included to use this macro. Instructions to include this via SBT are here.
You can use the above-defined macro like this:
@noop
case class Foo(a: String, b: Int)
@noop
object Bar {
def f(): String = "hello"
}
@noop
def g(): Int = 10
