[23] exhaustiveness signalling difference between javac and ecj

[stephan-herrmann]

• precise implementation of TypePattern.isUnconditional()

  • remove implementations in parent / sibling classes

• defer setting SwitchStatement.totalPattern until we know if a default case is present (otherwise we would generated inconsistent code for default).

• clarify that flagDuplicateDefault() flags only conditionally, renamed to checkDuplicateDefault()

  • inside this method clarify that only one error is reported per loc.

• remove all conflict reporting from CaseStatement.resolveCasePattern

  • will be done within SwitchStatement.resolve() anyway

• remove IProblem.DuplicateTotalPattern and related code

  • all errors reported here coincided with a dominance error

• adjust tests: no longer expect secondary errors

fixes https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2915

[stephan-herrmann]

@mpalat @srikanth-sankaran commit https://github.com/eclipse-jdt/eclipse.jdt.core/pull/2925/commits/f508a96cd748c7809ddb40aea278e7937f250657 fully removes IProblem.DuplicateTotalPattern and related code. This is probably worth another pair of eyeballs looking at that change.

You'll find an explanation in https://github.com/eclipse-jdt/eclipse.jdt.core/issues/2915#issuecomment-2335143598

[stephan-herrmann]

Merged in the interest of time.

Comments are still wellcome.