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[Clang] Implement CWG2496 #142975

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Merged
merged 4 commits into from
Jun 9, 2025
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[Clang] Implement CWG2496 #142975

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d4294fb
[Clang] Implement CWG2496
cor3ntin Jun 5, 2025
1f2f570
more tests
cor3ntin Jun 5, 2025
32d10af
more tests
cor3ntin Jun 5, 2025
6aee385
add tests
cor3ntin Jun 9, 2025
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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -155,6 +155,8 @@ Resolutions to C++ Defect Reports

- Implemented `CWG3005 Function parameters should never be name-independent <https://wg21.link/CWG3005>`_.

- Implemented `CWG2496 ref-qualifiers and virtual overriding <https://wg21.link/CWG2496>`_.

C Language Changes
------------------

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2 changes: 1 addition & 1 deletion clang/lib/Sema/SemaOverload.cpp
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Expand Up @@ -1490,7 +1490,7 @@ static bool IsOverloadOrOverrideImpl(Sema &SemaRef, FunctionDecl *New,
// If the function is a class member, its signature includes the
// cv-qualifiers (if any) and ref-qualifier (if any) on the function itself.
auto DiagnoseInconsistentRefQualifiers = [&]() {
if (SemaRef.LangOpts.CPlusPlus23)
if (SemaRef.LangOpts.CPlusPlus23 && !UseOverrideRules)
return false;
if (OldMethod->getRefQualifier() == NewMethod->getRefQualifier())
return false;
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31 changes: 31 additions & 0 deletions clang/test/CXX/drs/cwg24xx.cpp
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Expand Up @@ -215,3 +215,34 @@ void (*q)() throw() = S();
// since-cxx17-error@-1 {{no viable conversion from 'S' to 'void (*)() throw()'}}
// since-cxx17-note@#cwg2486-conv {{candidate function}}
} // namespace cwg2486


namespace cwg2496 { // cwg2496: 21
#if __cplusplus >= 201102L
struct S {
virtual void f(); // #cwg2496-f
virtual void g() &; // #cwg2496-g
virtual void h(); // #cwg2496-h
virtual void i();
virtual void j() &;
virtual void k() &&;
virtual void l() &;
};

struct T : S {
virtual void f() &;
// expected-error@-1 {{cannot overload a member function with ref-qualifier '&' with a member function without a ref-qualifier}}
// expected-note@#cwg2496-f {{previous declaration is here}}
virtual void g();
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I'd also like to see a case where it's declared as & in the base class and && in the derived class.

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I think this is l() case

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i added the l case afterwards :)

// expected-error@-1 {{cannot overload a member function without a ref-qualifier with a member function with ref-qualifier '&'}}
// expected-note@#cwg2496-g {{previous declaration is here}}
virtual void h() &&;
// expected-error@-1 {{cannot overload a member function with ref-qualifier '&&' with a member function without a ref-qualifier}}
// expected-note@#cwg2496-h {{previous declaration is here}}
virtual void i();
virtual void j() &;
virtual void k() &;
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Shouldn't this be diagnosed? k() && is in the base class.

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No, the two functions don't correspond.

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Ah, I see that wording now, you're right. And since they don't correspond, those are overloads not overrides.

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Can you leave a comment in the test about that?

virtual void l() &&;
};
#endif
}
2 changes: 1 addition & 1 deletion clang/www/cxx_dr_status.html
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Expand Up @@ -14811,7 +14811,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2>
<td><a href="https://cplusplus.github.io/CWG/issues/2496.html">2496</a></td>
<td>CD6</td>
<td><I>ref-qualifier</I>s and virtual overriding</td>
<td class="unknown" align="center">Unknown</td>
<td class="unreleased" align="center">Clang 21</td>
</tr>
<tr class="open" id="2497">
<td><a href="https://cplusplus.github.io/CWG/issues/2497.html">2497</a></td>
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