Playframework template WTF?

gistfile1.txt

// FINE!

@reports.zip(exec.Comparisons2.totalTimeColors).map { case (r@ElapsedTimeOf(title, elapsed ),color)  =>
      @{oneSeries(elapsed.time, title, "column", color, 0)}
  }.reduce(_ + (new Html(",")) + _)

---------------

// BAD! -> 
@reports.zip(exec.Comparisons2.totalTimeColors).map { 
  case (r@ElapsedTimeOf(title, elapsed ),color)  =>
      @{oneSeries(elapsed.time, title, "column", color, 0)}
  }.reduce(_ + (new Html(",")) + _)
  
Error:
[error] /Users/pedrofurla/dev/projects/slick/slick-perf/src/main/twirl/templates/plots3.scala.html:70: missing arguments for method elapsed in object Chronograph2;
[error] follow this method with `_' if you want to treat it as a partially applied function
[error]                 case (r@ElapsedTimeOf(title, elapsed ),color)  =>
[error]                                              ^