Runtime error in exhaustive switch

The following code doesn't work well in HL because the switch is not exhaustive at runtime:

```haxe
enum abstract A(String) {
var A;
var B;
}

class Test {
static function foo( e : A ) return { v : switch( e ) { case A: 55; case B: 66; } };
static function main() {
trace(foo(null));
trace(foo(cast "C")); // if loaded from JSON for example
}
}
```

I wonder if some other platforms are concerned - in which case this should be fixed in Haxe - I expect both results to be `{ v : 0 }`. BTW it is not reproducible with simply "return switch"