A new rule to make "else" a mandatory part of "case of"

[jwikman]

In our company we've made it mandatory to always have a else part in all case of statements, even if nothing should be done in that scenario.

If nothing should be done in the else part, we just add an empty statement with a comment, like this example:

case EnumValue of 
    SomeEnum::First:
       Message('Whatever);
    SomeEnum:Second:
        Message('Some message.');
    else
        ; // No other scenarios need a message
end;

(The empty statement with a comment is hopefully allowed soon if #747 gets implemented)

In this way the code reader know that this is fully intentional, compared to a missing else.

I suggest a new rule that makes else mandatory in all case of statements.

We also do a lot of telemetry (that creates alerts, with stack traces etc.) and throw errors in the else parts that should not be possible.
Like this:

case EnumValue of 
    SomeEnum::First:
       Message('Whatever);
    SomeEnum:Second:
        Message('Some message.');
    else
        TelemetryManagement.SendProgrammingErrorTelemetryAndThrowError('SomeEnum "%1" is not supported. This is a programming error.', EnumValue );
end;

A new rule would be a great help to identify if we've missed the else part somewhere.