[display] completion doesn't work for macro function arguments anymore

```haxe
class Main {
public static function main() {
foo("".);
}

static macro function foo(s:String) {
return macro {};
}
}
```

With preview 4, completion worked fine:


Now it errors with the following:

```
>haxe --display Main.hx@57
Main.hx:3: characters 9-10 : haxe.macro.Expr should be String
Main.hx:3: characters 9-10 : For function argument 's'
Main.hx:3: characters 9-10 : haxe.macro.Expr should be String
Main.hx:3: characters 9-10 : For function argument 's'
```