[display] var expressions in metas upset completion

I had some macros in haxe 3 project that used `var x: Type` expressions to specify a list of idents and types to use when generating fields.

For example
```haxe
@:event(var name: Type)
class Example {
}
```

While the code compiles, some weird side effects start happening in completion, for example, the field `name: Type` is suggested as if it were a field of other classes and macro-generated fields stop showing up in completion.

~~@nadako said vscode completion started hanging when trying the example~~

Here's a try-haxe: http://try-haxe.mrcdk.com/#F666c (Make sure to set haxe version to latest commit and try completion on line 13)