GADT type params and inlining

enum BinOp {
Like:BinOp;
}

abstract Expr(ExprData) {
inline function new(e) {
this = e;
}

@:from static function ofData(d:ExprData):Expr {
return new Expr(d);
}

public function like(b:Expr):Expr {
return EBinOp(Like, this, b);
}
}
```

My first question is whether the `like` method should compile? Because within that function `this` is `ExprData`, where `T` is supposed to be an unconstrained type parameter and it doesn't sound like it should pass the `T:String` constraint check of `Like`.

Secondly, if we add `inline` to the `ofData` method, we actually get an error talking about this:
```
src/Main.hx:19: characters 23-27 : error: Expr.T should be String
src/Main.hx:19: characters 23-27 : ... have: (ExprData) -> ...
src/Main.hx:19: characters 23-27 : ... want: (ExprData) -> ...
src/Main.hx:19: characters 23-27 : ... For function argument 'a'
```