SA1516 reported twice for the same location in top-level statements

[bjornhellander]

In a comment to #3482, @sharwell noted that some unit tests were expecting two diagnostics for the same location in top-level statements like this:

return 0;
record A(); // Reported twice on the first character of this line

I have debugged a little and see that HandleCompilationUnit in SA1516ElementsMustBeSeparatedByBlankLine is called twice in those tests. The second call only seems to happen on code using top-level statements.

[bjornhellander]

Seems to be bug in earlier Roslyn versions. It is only reported once in the new c# 11 test project (PR #3491).