gistfile1.txt

import scala.reflect.macros.Context

object Macros {
  implicit class NumericExtensions[T : Numeric](self: T) {
    def squared: T = macro squaredImpl[T]
  }

  def squaredImpl[T : c.WeakTypeTag](c: Context): c.Expr[T] = {
    import c.universe._
    val Apply(_, List(selfTree)) = c.prefix.tree
    val self = c.Expr[T](selfTree)
    val ev = c.Expr[Numeric[T]](c.inferImplicitValue(weakTypeTag[Numeric[T]].tpe))
    reify {
      implicit val n = ev.splice
      self.splice * self.splice
    }
  }
}

02:52 ~/Projects/Kepler_snippet01/sandbox (topic/snippet01)$ scalac Test.scala 
Test.scala:15: error: value * is not a member of type parameter T
      self.splice * self.splice
                  ^
one error found