Not all implicits should be able to influence type inference

[scabug]

As discussed in http://groups.google.com/group/scala-internals/browse_thread/thread/90927a689028dfe4

import scala.reflect.{ClassTag, classTag}
import scala.reflect.runtime.universe.{TypeTag, typeTag}

class C

object Test extends App {
  implicit val cctag: ClassTag[C] = ClassTag[C](classOf[C])
  def foo[T: ClassTag](xs: T*) = println(classTag[T])
  foo(1, 2)
  foo()

  implicit val cttag: TypeTag[C] = { val cttag = "shadow cttag"; typeTag[C] }
  def bar[T: TypeTag](xs: T*) = println(typeTag[T])
  bar(1, 2)
  bar()
}

10:15 ~/Projects/Kepler_5923/sandbox (ticket/5923)$ sr
Int
C
TypeTag[Int]
TypeTag[C]

Whereas one would expect the second and the fourth line to print Nothing and TypeTag[Nothing].

[scabug]

Imported From: https://issues.scala-lang.org/browse/SI-7454?orig=1
Reporter: @xeno-by

[scabug]

@xeno-by said (edited on May 7, 2013 10:41:39 AM UTC):
Let's try to pursue a better error message for the ambiguous implicit error. That's probably a lint material.