Variables not listed after NOT operator

I'm not sure if this is a bug or a missing feature.

Usually, variables get listed for code completion while typing:

```
var is_sunny_weather = true

if is_sun| # | is the text cursor and Zed would list "is_sunny_weather" in the appearing dropdown
```

However, it does not when there is a preceding NOT operator:

```
var is_sunny_weather = true

if !is_sun| # note the "!", and Zed does not list any local variables anymore
```

Any idea?