Is it possible to generate Apply from WeakTypeTag inside a scala macro?

Question

I have a WeakTypeTag of some type in my macro, and I want to generate code as follows:

macroCreate[SomeObject] // => SomeObject(1)


        

Answer 1

You can get the symbol of the companion object and then use the universe's Ident(sym: Symbol): Ident factory method:

def macroCreate[A] = macro _macroCreate[A]

def _macroCreate[A](c: Context)(implicit wtt: c.WeakTypeTag[A]) = {
  import c.universe._

  c.Expr(
    Apply(
      Select(Ident(wtt.tpe.typeSymbol.companionSymbol), newTermName("apply")),
      c.literal(1).tree :: Nil
    )
  )
}

And then:

scala> case class SomeObject(i: Int)
defined class SomeObject

scala> macroCreate[SomeObject]
res0: SomeObject = SomeObject(1)

scala> macroCreate[List[Int]]
res1: List[Int] = List(1)

If you really mean that SomeObject is the type of the object (i.e., not the type of its companion class), just remove the .companionSymbol above.