Don't put them in a fake expression.
This simplifies a bit the expression handling, and will make
possible to fix analysis that needs a vew into the aliases
As a result
- The error messages will now show the error with `-` instead of `_`
- The LSP will auto-complete with -
- The interpreter's list of properties will list the property with '-'
(but we made the change so that set_property, get_property, and so on
work also if passed a '-')
