Issue with GADTs tasty types

[nicolasstucki]

trait Map2[K] {
  def get(k: K) = null
  def foo = {
    this match {
      case that: Map2[b] => that.get(3.asInstanceOf[b])
      case that: Map2[c] => that.get(4.asInstanceOf[K])
      case _ => get(5.asInstanceOf[K])
    }
  }
}

gets wrong types for binding in 3.asInstanceOf[b] and 4.asInstanceOf[K] involving b and c.

The full tasty pretty printed is here.

[nicolasstucki]

In the first case the binding of b in missing the inferred upper bound on K.

                          Bind(UTF8: b)
                           type
                            SHARED(15)
                              TypeBounds
                               low:
                                TypeRef(UTF8: Nothing)
                                 qualType:
                                  TermRefPKG: UTF8: scala
                               high:
                                TypeRef(UTF8: Any)
                                 qualType:
                                  SHARED(19)
                                    TermRefPKG: UTF8: scala

[nicolasstucki]

The second case apply the binding instead of the type.

TypeApply
                            fun:
                              Select(Signed orig: [UTF8: asInstanceOf]() :[Qualified [Qualified [UTF8: java].[UTF8: lang]].[UTF8: Object]])
                               qual:
                                ...
                            args:
                              SHARED(154)
                                Bind(UTF8: c)
                                 type
                                  SHARED(15)
                                    TypeBounds
                                     low:
                                      TypeRef(UTF8: Nothing)
                                       qualType:
                                        TermRefPKG: UTF8: scala
                                     high:
                                      TypeRef(UTF8: Any)
                                       qualType:
                                        SHARED(19)
                                          TermRefPKG: UTF8: scala

[nicolasstucki]

These trees fail Ycheck after phase classOf if loaded.

This was discovered in #2910 and can be reproduced with the tests/link/on-custom-lib/map2.scala by uncommenting the code.

[nicolasstucki]

This code in present in strawman.collection.Map.equals.

[DarkDimius]

Taking over this blocker.

[DarkDimius]

Fix ready. It was easy.