Implicit type conversion

I have found what appears to be an anomaly in implicit type coercion. I
have attempted to trivialise my example, but it is still 50 or so LOC. I
have annotated the code with the relevant question in the relevant place
in the code with comments. The problem is that this code will not
compile. I expect that the code will compile successfully, or fail to
compile with 2 errors, yet it seems to fail only with 1 error. That is
to say, a contradiction exists from my perspective and I'd appreciate
any explanation that clarifies this situation for me, thanks.

Search for:
"why does this compile..."
and
"...while this does not compile?"

sealed abstract class CList[+A]
case object Nil extends CList[Nothing]
final case class Cons[+A](head: A, tail: CList[A]) extends CList[A]

sealed abstract class TriState
final case object ON extends TriState
final case object OFF extends TriState
final case object NEUTRAL extends TriState

object CList {
  implicit def string2CList(xs: String): CList[Char] = {
    // todo
    // inefficient, write imperative code
    // go on, you can do it.
    if(xs isEmpty)
      Nil
    else
      Cons(xs charAt 0, xs substring 1)
  }

  implicit def cList2String (xs: CList[Char]): String = {
    // todo
    ""
  }
}

object TriState {
  import CList._

  implicit def list2TriState(xs: CList[Char]): TriState = {
    if(xs == string2CList("1"))
      ON
    if(xs == string2CList("0"))
      OFF
    else
      NEUTRAL
  }
}

final case class X(ts: TriState) {

}

object Y {
  import CList.string2CList
  import TriState.list2TriState

  def f1(): X = {
    // why does this compile...
    val x: CList[Char] = "x"
    X(x)
  }

  def f2(): X = {
    // ...while this does not compile?
    // error: type mismatch;
    // found   : java.lang.String("x")
    // required: TriState
    X("x")
  }
}

-- 
Tony Morris
http://tmorris.net/

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