implicit val intToNumeric = new ToAst[Int] {
    type TypeMember = Numeric

  }

type Sequence[T]

type Produce{

def as[T](name: String)(implicit ast: ToAst[T]): ast.TypeMember = field(name).asInstanceOf[ast.TypeMember]
}

Seq(Produce[Int].as("foo"),Produce[Int].as("bar"))

MakeArray[(ToAst[Int] with Object {type TypeMember = Numeric})#TypeMember] which == Sequence[T]