type arguments are not substited in macroses defined inside type provider: https://issues.scala-lang.org/browse/SI-7849

gistfile1.txt

import org.scalatest._
import x._
import language.experimental.macros


class TieSpec extends FlatSpec  {

  "X" should "substitute macro argument" in {
    val x = X.xProvider;
    val a = new Arg[Int] {}
    x.f(a)
  }

}
~                      

gistfile2.txt

Output is

xtag = WeakTypeTag[H]
atag = WeakTypeTag[A]

//(must be Int instead A)

type aliases not substitied

package x

import language.experimental.macros
import scala.reflect.macros._
import scala.reflect.api._

trait Arg[A]
{
}


object X
{

  def xProvider = macro xProviderImpl

  def xProviderImpl(c:Context) =
  {
   import c.universe._
   /*
   val rtree = q"""
   {
    class H {
       def f[A](x:Arg[A]): Unit = macro X.fImpl[H,A]
    }
    new H { }
   }
   """
   */
   import Flag._
   val rtree=Block(List(ClassDef(Modifiers(), newTypeName("H"), List(), Template(List(Select(Ident(newTermName("scala")),
             newTypeName("AnyRef"))), emptyValDef, List(DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(),
             Block(List(Apply(Select(Super(This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())), Literal(Constant(())))),
             DefDef(Modifiers(MACRO), newTermName("f"), List(TypeDef(Modifiers(PARAM), newTypeName("A"), List(), TypeBoundsTree(
             Select(Select(Ident(nme.ROOTPKG), newTermName("scala")), newTypeName("Nothing")), Select(Select(Ident(nme.ROOTPKG),
             newTermName("scala")), newTypeName("Any"))))), List(List(ValDef(Modifiers(PARAM), newTermName("x"), AppliedTypeTree(
             Ident(newTypeName("Arg")), List(Ident(newTypeName("A")))), EmptyTree))), Ident(newTypeName("Unit")), TypeApply(
             Select(Ident(newTermName("X")), newTermName("fImpl")), List(Ident(newTypeName("H")), Ident(newTypeName("A"))))))))),
             Block(List(ClassDef(Modifiers(FINAL), newTypeName("$anon"), List(), Template(List(Ident(newTypeName("H"))), emptyValDef,
             List(DefDef(Modifiers(), nme.CONSTRUCTOR, List(), List(List()), TypeTree(), Block(List(Apply(Select(Super(
             This(tpnme.EMPTY), tpnme.EMPTY), nme.CONSTRUCTOR), List())), Literal(Constant(())))), EmptyTree)))), Apply(Select(New(
             Ident(newTypeName("$anon"))), nme.CONSTRUCTOR), List())))
   //System.err.println(showRaw(rtree))
   c.Expr[Any](rtree)
  }

  def fImpl[X,A](c:Context)(x: c.Expr[A])(implicit xtag: c.WeakTypeTag[X], atag: c.WeakTypeTag[A]) =
  {
    import c.universe._
    val xType = xtag.tpe
    val aType = atag.tpe
    Console.println("xtag = " + xtag)
    Console.println("atag = " + atag)
    reify{ () }
  }



}