How to manipulate modifiers in annotation macros

Question

How to manipulate modifiers? For example, I want to exclude Flaga.CASE in ClassDef modifiers. However, following causes a compile error.

case q"$mods class $name [..$tp](..$vals) extends ..$exts { ..$defs }" if mods.hasFlag(Flag.CASE) =>
       val m = mods - Flag.CASE
       q"$m class $name [..$tp](..$vals) { ..$defs }"

error is

[error] ...: value - is not a member of c.universe.Modifiers
[error]         val m = mods - Flag.CASE
[error]                      ^
[error] one error found

Ok, Modifiers api does not have - to exclude specified element (I expected this method works like Set's - if exists).

My question is, as I mentioned above, is there a method to manipulate Modifiers?

Answer 1

Try

import c.universe._

implicit class ModifiersOps(left: Modifiers) {
  def & (right: FlagSet): Modifiers = left match {
    case Modifiers(flags, privateWithin, annots) => Modifiers(flags & right, privateWithin, annots)
  }
}

implicit class FlagSetOps(left: FlagSet) {
  def & (right: FlagSet): FlagSet = (left.asInstanceOf[Long] & right.asInstanceOf[Long]).asInstanceOf[FlagSet]
  def unary_~ : FlagSet = (~ left.asInstanceOf[Long]).asInstanceOf[FlagSet]
}

annottees.head match {
  case q"${mods: Modifiers} class $name [..$tp](..$vals) extends ..$exts { ..$defs }" if mods.hasFlag(Flag.CASE) =>
    val m = mods & ~Flag.CASE
    q"$m class $name [..$tp](..$vals) { ..$defs }"
}