divergence.log

% tail -n100 sandbox/{macro,client}.scala && scalac sandbox/macro.scala && scalac sandbox/client.scala
==> sandbox/macro.scala <==
class TC[T]
case class C(nodes: List[C])
object Macro {
  import language.experimental.macros
  import reflect.macros.whitebox.Context
  def impl[T <: C: c.WeakTypeTag](c: Context): c.Expr[TC[T]] = {
    import c.universe._
    def proposal = q"""{
      implicit def m: TC[C] = ???
      implicitly[TC[List[C]]]
      ???
    }"""
    println("typechecked: " + c.typeCheck(proposal, silent = true, withMacrosDisabled = true))
    c.Expr[TC[T]](proposal)
  }

  implicit def m[T <: C]: TC[T] = macro impl[T]
  implicit def listTC[T: TC]: TC[List[T]] = new TC[List[T]]
}

==> sandbox/client.scala <==
class Client {
  import Macro._
  implicitly[TC[List[C]]]
}

warning: there was one deprecation warning; re-run with -deprecation for details
one warning found
typechecked: <empty>
typechecked: {
  implicit def m: TC[C] = scala.this.Predef.???;
  scala.this.Predef.implicitly[TC[List[C]]](Macro.listTC[C](m));
  scala.this.Predef.???
}
%