[Issue 7358] New: `final switch` over enum should add throwing default in debug mode at least

d-bugmail at puremagic.com d-bugmail at puremagic.com
Tue Jan 24 03:52:04 PST 2012


http://d.puremagic.com/issues/show_bug.cgi?id=7358

           Summary: `final switch` over enum should add throwing default
                    in debug mode at least
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: verylonglogin.reg at gmail.com


--- Comment #0 from Denis <verylonglogin.reg at gmail.com> 2012-01-24 14:52:00 MSK ---
Inspired by bug 5713, comment 5

Even if every enum member is present a default statement should be added at
least in debug mode to catch such situation if enum members doesn't cover every
possible value:
---
enum E { a = 1, b }
void f(E e) {
    final switch (e) {
        case E.a:
        case E.b:
    }
}
void g() {
    f(E.a | E.b); // like `f(cast(E)3);`, should throw
}
---

As was written in bug 5713 description:
>The purpose of "final switch" is to increase code safety compared to normal switches on enums.
So it's really bad that it works silently incorrect. Personally I have used
`final switch` carefully and thought about it's behavior in such situation
since it has been introduced because it is undocumented. So the documentation
should be fixed too.

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