Unsound behaviour allowed with return static

```hack
<<__ConsistentConstruct>>
abstract class C1 {
final public function __construct(private T $value) {}

public static function from(mixed $value): this {
return new static($value);
}

public function getValue() : T {
return $this->value;
}
}

final class C2 extends C1 {}

<<__EntryPoint>>
function main() : string {
return C2::from(10)->getValue();
}
```

**Expected behavior**

Some sort of typechecker error maybe?

**Actual behavior**

No error (but running this produces a `TypeError`)

**Environment**

hhvm 4.100

Would be very interested to know how this might be handled. Related issue here: https://github.com/vimeo/psalm/issues/5383