java.lang.ClassCastException on a trivial match

[strelec]

Compiler version

3.2.0-RC1
On 3.1.3 it is a compiler error instead (it should not be)

Minimized code

case class Composite[T](v: T)

def m(composite: Composite[_]): Unit =
  composite match {
    case Composite[Int](v) => println(v)
    case _ => println("OTHER")
  }

m(Composite("This is String"))

Output

java.lang.ClassCastException: class java.lang.String cannot be cast to class java.lang.Integer

Expectation

Print "OTHER"

[som-snytt]

#15356 explains the revised translation.

When written as an extractor, it correctly warns, so "constructor" pattern style should also warn:

-- Unchecked Warning: -------------------------------------------------------------------------------------------------------
3 |    case X[Int](v) => println(v)
  |         ^
  |         the type test for C[Int] cannot be checked at runtime

Edit: actually, I don't understand the new meaning, where the X is a non-case class with an unapply (Baz in the test).