Out of memory while producing Type Mismatch error message

[panacekcz]

This code (based on i3965.scala; notice the added intersection) should not compile. However, the compiler seems to get in some sort of infinite recursion, runs for a few minutes and then fails with Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded.

trait T
trait SortedSetOps[CC[X], C]
class TreeSet[A] extends SortedSetOps[TreeSet, TreeSet[A]]

class Test {
  def optionSequence1[CC[X] <: (SortedSetOps[CC, CC[X]] & T) , A](xs: CC[A]): Unit = ()
  def test(xs2: TreeSet[String]) = {
    optionSequence1(xs2)
  }
}

(If & T is removed, or with T is added to TreeSet, it compiles fine.)

This variant also fails, but it possibly could compile by inferring CC to be [X] => (TreeSet[X] & T):

trait T
trait SortedSetOps[CC[X], C]
class TreeSet[A] extends SortedSetOps[[X] => (TreeSet[X] & T), TreeSet[A] & T]

class Test {
  def optionSequence1[CC[X] <: (SortedSetOps[CC, CC[X]] & T) , A](xs: CC[A]): Unit = ()
  def test(xs2: TreeSet[String] & T) = {
    optionSequence1(xs2)
  }
}

When the type parameters are specified explicitly, optionSequence1[[X] => (TreeSet[X] & T), String](xs2), it compiles fine.

[panacekcz]

Actually, in the first case, the intersection is not important. The problem is that there is a type mismatch and the compiler seems to get stuck trying to produce the error message.
Simplified test:

trait SortedSetOps[CC[X], C]
class TreeSet[A] extends SortedSetOps[TreeSet, TreeSet[A]]

class Test {
  def optionSequence1[CC[X] <: SortedSetOps[CC, CC[X]] , A](xs: CC[A]): Unit = ()

  def test(xs2: Int) = {
    optionSequence1(xs2)
  }
}

If I remove the applications of the reported type map in ErrorReporting.Errors.typeMismatchMsg, then I get this type mismatch error:

-- [E007] Type Mismatch Error: i3965Error.scala:8:20 ---------------
8 |    optionSequence1(xs2)
  |                    ^^^
  |found:    Int(xs2)
  |required: CC[A]
  |
  |where:    A  is a type variable
  |          CC is a type variable with constraint <: [X] => SortedSetOps[LazyRef(CC), LazyRef(CC[X])]
one error found

That means reported needs some kind of protection against infinite recursion.