Improve the warning/error message, `expected identifier` to correctly identify the issue

[adhadse]

Adding extra , at the end of a widget written inside a view macro generates this vague warning and error: Removing the extra comma make it go away:

Other times, I came across this when trying to add a named child to GtkStack: Which should be resolved using a ::

What can be done to improve the user to understand the underlying problem neatly?

[AaronErhardt]

Thanks for your report! Does this issue still appear in 0.6?

Also, the last error is valid though, no?

[adhadse]

Yes, I'm on 0.6.

The last error does confuse me, probably it could be just Did you confuse with =/: ... warning would have made sense 🤔

[AaronErhardt]

I've just merged #470 which fixes the first issue. The second issue needs a little bit more work, but it is not too bad IMO because it makes sense that the macro expects an identifier after a =.