"debugging" scala annotation macros - scala

Question

some of my scala annotation macro do not seem to get expanded, is there a way to inspect/log which expression gets passed to my annotation macro at compile time, because right now the code doesn't even compile...
def virtualize(tree: Tree): Tree = atPos(tree.pos) {
tree match {
case x =>
println("LOG: "+tree) //will only be printed during runtime
c.warning(tree.pos, "LOG: "+tree) //will only generate code for a warning
super.transform(tree)
}
}
Is there a way to issue compiler warnings in annotation macros?
Thanks a lot!

Answer 1

if you use idea then open terminal enter sbt ~compilewill Time compilation
then you can see compilation info log like follow in the terminal :
D:\git\scala-macro-example>sbt ~compile
[info] Loading project definition from D:\git\scala-macro-example\project
[info] Set current project to scala-macro-example (in build file:/D:/git/scala-macro-example/)
[info] Updating {file:/D:/git/scala-macro-example/}root...
[info] Resolving jline#jline;2.12.1 ...
[info] Done updating.
[info] Compiling 2 Scala sources to D:\git\scala-macro-example\module\macros\target\scala-2.11\classes...
[error] D:\git\scala-macro-example\module\macros\src\main\scala\macross\teach\WithHello.scala:16: type ClassWithFunc is not a member of package macross.annotat
ion
[error] class WithHelloImpl(val c: Context) extends macross.annotation.ClassWithFunc{
[error]
after
object ShowInfo {
class Show extends StaticAnnotation {
def macroTransform(annottees: Any*): Any = macro ShowImpl.apply
}
class ShowImpl(val c: Context) {
import c.universe._
def showInfo(s: String) =
c.info(c.enclosingPosition, s.split("\n").mkString("\n |---macro info---\n |", "\n |", ""), true)
def apply(annottees: c.Expr[Any]*): c.Expr[Any] = {
val a: Seq[c.universe.Tree] = annottees.map(_.tree)
showInfo(show(a.head))
c.Expr[Any](Block(a.toList, Literal(Constant(()))))
}
}
}
useing like following:
object ShowInfoUsing {
trait SuperTrait
class SuperClass
#ShowInfo.Show
class ShowInfoUsing(val i: Int = 1) extends SuperClass with SuperTrait {
def f = 1
val a = 1
}
}
you can see info logo in the terminal
[info] |---macro info---
[info] |class ShowInfoUsing extends SuperClass with SuperTrait {
[info] | <paramaccessor> val i: Int = _;
[info] | def <init>(i: Int = 1) = {
[info] | super.<init>();
[info] | ()
[info] | };
[info] | def f = 1;
[info] | val a = 1
[info] |}
[info] #ShowInfo.Show
[info]