反射 – Scala宏注释上的类型参数

trait MyTrait {
  def x: Int
  def y: Float
}

@MyAnnotation class MyClass //<-- somehow,this annotation should reference MyTrait

class MyAnnotation(val target: Any) extends StaticAnnotation {
  def macroTransform(annottees: Any*) = macro MyAnnotationImpl.impl
}
object MyAnnotationImpl {
  def impl(c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
    // if I can get a handle on the type MyTrait in here
    // then I can call .members on it,etc.
    ...
  }
}

基本上,与Using Scala reflection in Scala macros相同,除了使用宏注释.但是,当我尝试使用TypeTag模拟我的宏注释时

class MyAnnotation[T](val target: Any) extends StaticAnnotation {
  def macroTransform[T](annottees: Any*) = macro MyAnnotationImpl.impl[T]
}
object MyAnnotationImpl {
  def impl[T: c.WeakTypeTag](c: Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
    ...
  }
}

我明白了

[error] /Users/imran/other_projs/learn_macros/macros/src/main/scala/com/imranrashid/oleander/macros/MacrosWithReflection.scala:7: macro annotation has wrong shape:
[error]   required: def macroTransform(annottees: Any*) = macro ...
[error]   found   : def macroTransform[T](annottees: Any*) = macro ...
[error] class MyAnnotation[T](val target: Any) extends StaticAnnotation {
[error]       ^

我也尝试将类型作为我的注释的参数,所以我会使用它像@MyAnnotation(MyTrait)类Foo ….我可以将名称提取为类似于字符串的类似

val targetTrait = c.prefix.tree match {
  case Apply(Select(New(Ident(_)),nme.CONSTRUCTOR),List(Ident(termName))) => termName
}

但是,我不知道我能做什么,而那个String可以取回完整的类型.我也试过像@MyAnnotation(typeOf [MyTrait])类Foo …这样的变种,然后在我的宏里面的typeOf上使用c.eval,但是它也没有编译.