So I have an annotation on a function (DefDef). This annotation has parameters. However, I am confused on how to get the parameters from the constructor.
Usage example:
class TestMacro {
@Foo(true)
def foo(): String = ""
foo
}
Here's the code for the annotation:
class Foo(b: Boolean) extends StaticAnnotation {
def macroTransform(annottees: Any*) = macro Foo.impl
}
object Foo {
def impl(c: whitebox.Context)(annottees: c.Tree*): c.Expr[Any] = {
import c.universe._
//how do I get value of `b` here???
c.abort(c.enclosingPosition, "message")
}
}
What about this:
val b: Boolean = c.prefix.tree match {
case q"new Foo($b)" => c.eval[Boolean](c.Expr(b))
}
For sake of completeness this is the full source:
import scala.reflect.macros.Context
import scala.language.experimental.macros
import scala.annotation.StaticAnnotation
import scala.annotation.compileTimeOnly
import scala.reflect.api.Trees
import scala.reflect.runtime.universe._
class Foo(b: Boolean) extends StaticAnnotation {
def macroTransform(annottees: Any*) :Any = macro FooMacro.impl
}
object FooMacro {
def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
import c.universe._
val b: Boolean = c.prefix.tree match {
case q"new Foo($b)" => c.eval[Boolean](c.Expr(b))
}
c.abort(c.enclosingPosition, "message")
}
}