class Yo[Unused] {
  def yo(hasDefault: Any = ""): String = ""
}
 
class MacroNotExpanded {
  def toYo[Unused](a: Any)(implicit ct: reflect.ClassTag[Unused]): Yo[Unused] = new Yo[Unused]
  toYo("").yo()  
}

  /** Performs macro expansion on all subtrees of a given tree.
   *  Innermost macros are expanded first, outermost macros are expanded last.
   *  See the documentation for `macroExpand` for more information.
   */
  def macroExpandAll(typer: Typer, expandee: Tree): Tree =
    new Transformer {
      override def transform(tree: Tree) = super.transform(tree match {
        // todo. expansion should work from the inside out
        case tree if (delayed contains tree) && calculateUndetparams(tree).isEmpty && !tree.isErroneous =>
          val context = tree.attachments.get[MacroRuntimeAttachment].get.typerContext
          delayed -= tree
          context.implicitsEnabled = typer.context.implicitsEnabled
          context.enrichmentEnabled = typer.context.enrichmentEnabled
          context.macrosEnabled = typer.context.macrosEnabled
          macroExpand(newTyper(context), tree, EXPRmode, WildcardType)
        case _ =>
          tree
      })
    }.transform(expandee)

  /** Without any restrictions on macro expansion, macro applications will expand at will,
   *  and when type inference is involved, expansions will end up using yet uninferred type params.
   *
   *  For some macros this might be ok (thanks to TreeTypeSubstituter that replaces
   *  the occurrences of undetparams with their inferred values), but in general case this won't work.
   *  E.g. for reification simple substitution is not enough - we actually need to re-reify inferred types.
   *
   *  Luckily, there exists a very simple way to fix the problem: delay macro expansion until everything is inferred.
   *  Here are the exact rules. Macro application gets delayed if any of its subtrees contain:
   *    1) type vars (tpe.isInstanceOf[TypeVar]) // [Eugene] this check is disabled right now, because TypeVars seem to be created from undetparams anyways
   *    2) undetparams (sym.isTypeParameter && !sym.isSkolem)
   */
  var hasPendingMacroExpansions = false
  private val forced = perRunCaches.newWeakSet[Tree]
  private val delayed = perRunCaches.newWeakMap[Tree, scala.collection.mutable.Set[Int]]()