no type arguments for views?

@refried originally filed as https://github.com/playframework/playframework/issues/2194. migrating it here

views/foo1.scala.txt (won't compile)

@[L<:shapeless.Nat:shapeless.ops.nat.ToInt](bar: Bar[L])

@bar has size @shapeless.Nat.toInt[L]

views/foo2.scala.txt (will compile, but silly!)

@(bar: Bar[_<:shapeless.Nat], size: Int)

@bar has size @size

controllers/Application.scala

package controllers

import play.api._
import play.api.mvc._
import shapeless.Nat
import shapeless.ops.nat.ToInt

class Bar[L<:Nat]

object Application extends Controller {

  def index = Action {
    Ok(views.html.index("Your new application is ready."))
  }

  // won't compile
  def foo1 = views.txt.foo1(new Bar[Nat._3])

  // needlessly complicated
  def foo2 = {
    def barSize[L<:Nat:ToInt](bar: Bar[L]): Int = Nat.toInt[L]
    val bar = new Bar[Nat._3]
    val size = barSize(bar)
    views.txt.foo2(bar, size)
  }
}

The reproducer is in views/foo1.scala.txt and controllers/Application.scala; compare it with the compiling workaround in views/foo2.scala.txt. Start by reproducing the template compilation failure and trace how the type argument and context bounds are handled. Done means foo1 compiles without passing the separately calculated size used by foo2.