Patmat: dotty does not generate null checks for extractors

[DarkDimius]

object Test {
 case class MyTuple(a: Int, b: Int)
 def foo = MyTuple(1,2)
 def main(args: Array[String]): Unit = {
   val MyTuple(a,b) = null // should throw MatchError. Throws NPE instead.
   println(a + b)
 }
}

Scala2 style option-based pattern matching is handled correctly. This bug only happens with option-less pattern matching.

[DarkDimius]

This is a low-hanging fruit that may be a good introduction into PatternMatcher.

[jvican]

This code snippet doesn't compile in Scala:

<console>:15: error: constructor cannot be instantiated to expected type;
 found   : Test.MyTuple
 required: Null
          val MyTuple(a,b) = null

In my opinion, this shouldn't typecheck, while the following should both typecheck and throw a MatchError as @DarkDimius said:

object Test {
 case class MyTuple(a: Int, b: Int)
 def foo = MyTuple(1,2)
 def main(args: Array[String]): Unit = {
   def bla: MyTuple = null // this is probably gonna be defined in another scope
   val MyTuple(a,b) = bla // should throw MatchError. Throws NPE instead.
   println(a + b)
 }
}

Is there any way we can make the first code snippet fail to typecheck? I'm planning to make Dotty throw a MatchError in my last code snippet.