Type parameter ignored in selectDynamic invocation

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As noticed by Dinko Srkoc in http://thread.gmane.org/gmane.comp.lang.scala.user/58246 sometimes the type parameter on a selectDynamic call gets lost.

With this definition:

import language.dynamics

class C(v: Any) extends Dynamic {
  def selectDynamic[T](n: String): Option[T] = Option(v.asInstanceOf[T])
  def applyDynamic[T](n: String)(): Option[T] = Option(v.asInstanceOf[T])
}

one gets this behaviour:

scala> new C(42).foo[Int].get
java.lang.ClassCastException: java.lang.Integer cannot be cast to scala.runtime.Nothing$

This happens because in Typers.scala, mkInvoke is called with the following cxTree:
new C.(42).foo[Int].get

Note that the outer element of that tree is a Select(..., "get"), and that's not handled by mkInvoke:

  val (outer, explicitTargs) = cxTree1 match {
    case TypeApply(fun, targs)              => (fun, targs)
    case Apply(TypeApply(fun, targs), args) => (Apply(fun, args), targs)
    case t                                  => (t, Nil)
  }

That can be fixed by adding another case:

  val (outer, explicitTargs) = cxTree1 match {
    case TypeApply(fun, targs)              => (fun, targs)
    case Apply(TypeApply(fun, targs), args) => (Apply(fun, args), targs)
    case Select(TypeApply(fun, targs), nme) => (Select(fun, nme), targs)
    case t                                  => (t, Nil)
  }

With that change, the examples work as expected:

scala> new C(42).foo[Int]().get
res0: Int = 42

scala> new C(42).foo[Int].get
res1: Int = 42 

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Imported From: https://issues.scala-lang.org/browse/SI-6663?orig=1
Reporter: Jan Niehusmann (jannic)

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@paulp said:
Nice job, you're almost there! Sending a pull request with the fix and a test case makes our lives tremendously easier.

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Jan Niehusmann (jannic) said:
Maybe a duplicate of #6320

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Jan Niehusmann (jannic) said:
There are similar cases not covered by the mentioned patch:

scala> new C(42).foo[String].get
java.lang.ClassCastException: java.lang.Integer cannot be cast to java.lang.String

scala> new C(42).foo[String].get : Int
res2: Int = 42

Here, the [String] parameter is ignored, again. This time because the cxTree starts with the type annotation: (new C.(42).foo[String].get: Int)

Is there an easy way to find everything which can possibly get attached to cxTree?

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Jan Niehusmann (jannic) said:
scala/scala#1619

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Jan Niehusmann (jannic) said:
I'd guess that there are other possible contents of cxTree not yet handled. Is there a better way to fix this than to add all such cases manually to mkInvoke?

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Jan Niehusmann (jannic) said:
pull request against 2.10.x at scala/scala#1621

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@paulp said:
That PR was merged, but this is not fixed in general; scala/scala#1681 should fix them all.

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@paulp said:
edbcc64