Add helpful message when using @Assisted with @Inject

[vadym-shavalda]

Been bitten by this (arguably, because of my lack of attention at the moment).

Before:

After:

UPD:

[bcorso]

Thanks for the pull request!

This isn't quite the right place to add this message. The fix here should go into the InjectValidator instead, which is responsible for ensuring the @Inject/@AssistedInject constructor is valid. Reporting the issue in InjectValidator should prevent reaching this checkState when its invalid.

To clarify, the issue with your current solution is that throwing an exception in an annotation processor to report "user issues" is typically bad practice because it immediately stops the compilation and prevents our processor (and others) from reporting any additional issues. Instead there's a special mechanism for reporting errors in annotation processors (e.g. Messager in javac) which should be use to report user issues.

[vadym-shavalda]

Hey, Brad! Thanks for the swift review and pointers on how to implement this properly!
I'm not that familiar with the architecture yet, so opted for quick 'n dirty fix.

Does this look better?

[bcorso]

Yes, this is more like what I was thinking.

Unfortunately, there's no way to merge your PR directly from GitHub, so I'll need to patch in your change (I can still credit you with the commit). I'll try to find some time to do that today.

[vadym-shavalda]

No worries, and thank you!

I'll close the PR, then.
Please, let me know if anything else is needed from my side.
Cheers.