strange generic types matching

[Georgii Dernovyi]

I found subj for me (sc 2.11.8)

val s = Seq(Some(1))

s match{
  case h: List[String] => h(0)
  case   _ => 8
}

output:

s: Seq[Some[Int]] = List(Some(1))

res0: Any = Some(1) //???? 

Another weirdness

val s = Seq(Some(1))

s match{
  case h: List[Int] => h(0)
  case   _ => 8
}
output:
s: Seq[Some[Int]] = List(Some(1))

java.lang.ClassCastException: scala.Some cannot be cast to java.lang.Integer
	at scala.runtime.BoxesRunTime.unboxToInt(test.sc:97)
	at #worksheet#.#worksheet#(test.sc:4)

Is the compiler able to match generic types?

[Serge]

>Is the compiler able to match generic types?

No.

See warning:

Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_91).
Type in expressions for evaluation. Or try :help.

scala> val s = Seq(Some(1))

s: Seq[Some[Int]] = List(Some(1))

scala> s match{

| case h: List[String] => h(0)
| case _ => 8
| }

<console>:14: warning: non-variable type argument String in type pattern List[String] (the underlying of List[String]) is unchecked since it is eliminated by erasure

case h: List[String] => h(0)

^
res0: Any = Some(1)

[Georgii Dernovyi]

Thanks! Is it only for me obvious that it is a big compiler lack? :) I have to redesign my program, write a lot junk code just because Scala follows the questionable standpoint far from obvious logic ? Hmm 

[Oleksandr Olgashko]

Type erasure is more jvm (rather than scala) issue. For jvm, List[Foo] == List[Bar] == List[String] == List[Object] at runtime.

You can try typetags / classtags, they might be useful.