[ide] switch completion vs GADT-restricted cases

As I [recently learned](https://github.com/haxetink/tink_state/pull/53), it is possible to restrict enum variants to specific GADT instances, e.g. this works fine:

```haxe
enum E {
A;
B;
C:E;
}

function main() {
var o:E = A;
switch o {
case A: trace("a");
case B: trace("b");
}
}
```

However the postfix `.switch` completion still generates `case C` in this case, which will of course fail to compile: