[PATCH] D57438: [Sema][ObjC] Allow declaring ObjC pointer members in C++ unions under ARC

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak added inline comments.


================
Comment at: test/SemaObjCXX/arc-0x.mm:164
+    union {
+      union { // expected-note 2 {{'S1' is implicitly deleted because variant field '' has a non-trivial}} expected-note 4 {{'S1' is implicitly deleted because field '' has a deleted}}
+        id f0; // expected-note 2 {{'' is implicitly deleted because variant field 'f0' is an ObjC pointer}}
----------------
rjmccall wrote:
> ahatanak wrote:
> > The diagnostic message here should say the special function is deleted because the anonymous union's corresponding special function is deleted, but when diagnosing a deleted copy assignment operator, it says the anonymous union's special function is non-trivial. I'm not sure this is a bug, but I see the same diagnostic message when I compile the following non-ObjC code:
> > 
> > ```
> > struct S0 {
> >   S0(const S0 &);
> >   S0 &operator=(const S0 &);
> >   int *p;
> > };
> > 
> > struct S1 {
> >   union {
> >     union { // copy assignment operator of 'S1' is implicitly deleted because variant field '' has a non-trivial copy assignment operator
> >       S0 s10;
> >       int b;
> >     };
> >     int c;
> >   };
> >   ~S1();
> > };
> > 
> > S1 *x0;
> > 
> > void testC1(S1 *a0) {
> >   *a0 = *x0; // error: object of type 'S1' cannot be assigned because its copy assignment operator is implicitly deleted
> >   *a0 = static_cast<S1&&>(*x0); // error: object of type 'S1' cannot be assigned because its copy assignment operator is implicitly deleted
> > }
> > ```
> > 
> > It seems that this happens because the following code in `Sema::ShouldDeleteSpecialMember` is preventing the method declaration from being marked as deleted:
> > 
> > ```
> >   // For an anonymous struct or union, the copy and assignment special members
> >   // will never be used, so skip the check. For an anonymous union declared at
> >   // namespace scope, the constructor and destructor are used.
> >   if (CSM != CXXDefaultConstructor && CSM != CXXDestructor &&
> >       RD->isAnonymousStructOrUnion())
> >     return false;
> > ```
> Well, if it's not different from the ordinary C++ treatment, I think we can justify just improving QoI there separately.
I filed PR40555 to fix the C++ case.


Repository:
  rC Clang

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  https://reviews.llvm.org/D57438/new/

https://reviews.llvm.org/D57438