Implicit lookup fails for implicit def which returns a path-dependent type

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In the following code, the 2nd call to f at the end fails to find the implicit value of type GetResult[(String, String)]. The version with the explicit getTuple call succeeds.

object TupledEvidenceTest {

  abstract class TupledEvidence[M[_], T] { type T }

  implicit def witnessTuple2[M[_], T1, T2](implicit ev1: M[T1], ev2: M[T2]):
    TupledEvidence[M, (T1, T2)] { type T = (T1, T2) } = sys.error("")

  class GetResult[T]

  implicit val getString = new GetResult[String]

  implicit def getTuple[T](implicit w: TupledEvidence[GetResult, T]): GetResult[w.T] = sys.error("")

  def f[T : GetResult] = ""

  f[(String,String)](getTuple[(String, String)])

  f[(String,String)]
}

Both calls work if you use the following version of getTuple without the path-dependent return type.

  implicit def getTuple[T](implicit w: TupledEvidence[GetResult, T]): GetResult[T] = sys.error("")

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Imported From: https://issues.scala-lang.org/browse/SI-5643?orig=1
Reporter: @szeiger
Affected Versions: 2.9.1, 2.10.0
See #5070

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@retronym said:
Sounds related to {{DependentTypeMap}}, see the comments here: https://issues.scala-lang.org/browse/SI-5070?focusedCommentId=57733&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-57733

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@adriaanm said:
Unassigning and rescheduling to M6 as previous deadline was missed.