[PATCH] Implement DR85: Redeclaration of member class

[David Majnemer]

On Mon, Jun 10, 2013 at 3:44 PM, Richard Smith <richard at metafoo.co.uk>wrote:

> It'd be useful to keep one testcase of this within a class template.
> Also, please keep the diagnostic as an ExtWarn.
>

Done and done.


>
> On Mon, Jun 10, 2013 at 3:21 PM, David Majnemer
> <david.majnemer at gmail.com> wrote:
> > On Mon, Jun 10, 2013 at 12:56 PM, Richard Smith <richard at metafoo.co.uk>
> > wrote:
> >>
> >> On Mon, Jun 10, 2013 at 11:41 AM, David Majnemer
> >> <david.majnemer at gmail.com> wrote:
> >> > On Mon, Jun 10, 2013 at 9:14 AM, Jordan Rose <jordan_rose at apple.com>
> >> > wrote:
> >> >>
> >> >> The text says "already-defined", but in the first case it's merely
> >> >> declared twice.
> >> >
> >> >
> >> > Fixed.
> >> >
> >> >>
> >> >>
> >> >> If there's really no better justification than "because the standard
> >> >> says
> >> >> so", why not make this Ext or ExtWarn instead of Error? Clearly we
> >> >> already
> >> >> have this working.
> >> >
> >> >
> >> > I made it ExtWarn and gave it the flag -Wmember-class-redeclared.
> >>
> >> In C++11, the relevant text is: "A member shall not be declared
> >> twice in the member-specification, except that a nested class or
> >> member class template can be declared and
> >> then later defined, and except that an enumeration can be introduced
> >> with an opaque-enum-declaration and
> >> later redeclared with an enum-specifier."
> >>
> >>
> >> Please add tests for the union and enum cases too, and make sure the
> >> patch correctly handles them.
> >>
> >> struct A {
> >>   union U;
> >>   union U {}; // ok
> >>   union U; // error
> >>
> >>   enum E1 : int;
> >>   enum E1 : int { e1 }; // ok
> >>   enum E1 : int; // error
> >>
> >>   enum class E2;
> >>   enum class E2 { e2 }; // ok
> >>   enum class E2; // error
> >> };
> >
> >
> > Done.
> >
> >>
> >>
> >> >> Jordan
> >> >>
> >> >>
> >> >> On Jun 9, 2013, at 23:51 , David Majnemer <david.majnemer at gmail.com>
> >> >> wrote:
> >> >>
> >> >> The attached patch implements DR85 [*] which disallows the existence
> of
> >> >> a
> >> >> declaration of a member class that isn't a forward declaration before
> >> >> it's
> >> >> definition.
> >> >>
> >> >> This means that the following would be disallowed:
> >> >> class A {
> >> >>   struct B; // note here
> >> >>   struct B; // error here
> >> >> };
> >> >>
> >> >> as well as:
> >> >> class C {
> >> >>   struct B {}; // note here
> >> >>   struct B; // error here
> >> >> };
> >> >>
> >> >> I'm very open to suggestions on the diagnostic, I couldn't think of a
> >> >> great one that doesn't boil down to "this is forbidden because the
> >> >> standard
> >> >> says so."
> >> >>
> >> >> [*] http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#85
> >> >>
> >> >> Thanks
> >> >> --
> >> >> David Majnemer
> >> >>
> >> >>
> >> >> _______________________________________________
> >> >> cfe-commits mailing list
> >> >> cfe-commits at cs.uiuc.edu
> >> >> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> >> >>
> >> >>
> >> >>
> >> >
> >> >
> >> > _______________________________________________
> >> > cfe-commits mailing list
> >> > cfe-commits at cs.uiuc.edu
> >> > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> >> >
> >
> >
>
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