Missed issues in editor

A little bit strange, but the IDEA editor doesn't show any errors for the following code:
```
var b //must have assignment
func fun(){
return //must return something
}
```

I have checked the same example in ANTLRv4 plugin and it shows 2 errors.

Reproduce the supplied code in the IDEA editor and compare its diagnostics with the ANTLRv4 plugin, which reports two errors. Trace the editor's error-reporting entry point and verify that both missing assignment and missing return diagnostics appear when the issue is fixed.

Written by the indexing model from the issue text.