DSLD: missing content assist proposals for isThisType pointcut

Consider the following:
```dsld
contribute(isScript() & isThisType()) {
  property name: 'xyz'
}
```

```groovy
/*
 * blah blah blah
 */

import java.util.regex.Pattern

def abc = 123

|
```

Invoking content assist (Ctrl+Space) at `|` is not showing a proposal for the DSLD-contributed property "xyz".