Hidden code suggestions are not tested

[SNCPlay42]

The enum SuggestionStyle (which is used by DiagnosticBuilder functions like span_suggestion_short) allows for code suggestions to not be displayed in compiler output, but still be made available to tools like IDE quick-fix and cargo fix, if it is obvious from the diagnostics what should be done.

But UI tests only check compiler output, so such suggestions are not being tested to see if they are valid/good/etc.

@rustbot modify labels: +A-diagnostics +A-suggestion-diagnostics +A-testsuite

[estebank]

All span_suggestion_short and span_suggestion_hidden cases should have tests using // run-rustfix to confirm their successful application. We probably need to audit that we are currently doing so.