Try to use '{...} rather than '[...]

x.asType match {
  case '[t] => '{tag[t]} match {
    case '{type t1 <: S; tag[`t1`]} =>
      '{ apply[t] }.asExprOf[Any]
  }

// outside macro impl
def tag[A] = ???

In scala 3.6.4, how to call a polymorphic method with type bounds from inside a quoted expression?