Improve warning for inferring an undesirable type

[jder]

Adds a fixit for the warning about inferring a probably-unexpected type, and adds another case for when inferring a type of [()]. It would be easy to also warn for arrays of any of the existing cases but this seemed like overkill and would require some additional messages.

Taken together, this:

let y = x.map { print($0) }

Now produces:

warning: variable 'y' inferred to have type '[()]'
add an explicit type annotation to silence this warning

With a fixit to add : [()] after y.

Resolves SR-11511.

[theblixguy]

Looks great, thanks!

[theblixguy]

@swift-ci please smoke test

[theblixguy]

You’ve got one failing SourceKit test which needs to be updated

[theblixguy]

@swift-ci please smoke test

[jder]

Thanks, sorry about that. I believe it should be fixed now, but I was just trying to verify locally before pinging you again. Is check-swift the full set that CI runs?

[theblixguy]

No worries... it runs primary tests and validation tests, so check-swift-validation.

[jrose-apple]

cc @hborla @xedin too

[jder]

OK, I just used the version in ConstraintSystem since they're both in sema. If that seems ok, I think this is ready to merge. (cc @theblixguy)

[theblixguy]

Hmm feels a little strange to import the ConstraintSystem just for a small check, but fine, we can change it when #27195 lands...or we can just duplicate the check here. What do others think?

[jder]

Yeah, it's true. I'm happy to change it when the other PR lands, or just copy-paste the code for now if that's preferable.

[jrose-apple]

I was going to say it's simple enough to just expand inline, but this is fine too.

[jder]

OK, then I think this is ready to merge after another smoke test run.

[theblixguy]

@swift-ci please smoke test

[jder]

Thanks, all. I just made the requested change, merged with master and ran check-swift-validation locally if someone (maybe @theblixguy or @xedin) could do a last check & merge.

[theblixguy]

@swift-ci please smoke test

[jder]

Seems like it passed! Would you be able to merge it @theblixguy?

[theblixguy]

Thank you for your contribution! Please don’t forget to mark the JIRA ticket as resolved :)

[jder]

Thank you as well!

[BasThomas]

Awesome!