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[Clang] Only ignore special methods for unused private fields in BuildFieldReferenceExpr #116965

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[Clang] Only ignore special methods for unused private fields in BuildFieldReferenceExpr #116965

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[Clang] Only ignore special methods for unused private fields in Buil…
Maetveis Nov 20, 2024
acffeca
Add Release Notes and comments to test
Maetveis Nov 25, 2024
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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -585,6 +585,8 @@ Improvements to Clang's diagnostics
- For an rvalue reference bound to a temporary struct with an integer member, Clang will detect constant integer overflow
in the initializer for the integer member (#GH46755).

- Fixed a false negative ``-Wunused-private-field`` diagnostic when a defaulted comparison operator is defined out of class (#GH116961).

Improvements to Clang's time-trace
----------------------------------

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12 changes: 10 additions & 2 deletions clang/lib/Sema/SemaExprMember.cpp
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Expand Up @@ -1874,8 +1874,16 @@ Sema::BuildFieldReferenceExpr(Expr *BaseExpr, bool IsArrow,
Context.getAttributedType(attr::NoDeref, MemberType, MemberType);
}

auto *CurMethod = dyn_cast<CXXMethodDecl>(CurContext);
if (!(CurMethod && CurMethod->isDefaulted()))
auto isDefaultedSpecialMember = [this](const DeclContext *Ctx) {
auto *Method = dyn_cast<CXXMethodDecl>(CurContext);
if (!Method || !Method->isDefaulted())
return false;

return getDefaultedFunctionKind(Method).isSpecialMember();
};

// Implicit special members should not mark fields as used.
if (!isDefaultedSpecialMember(CurContext))
UnusedPrivateFields.remove(Field);

ExprResult Base = PerformObjectMemberConversion(BaseExpr, SS.getScopeRep(),
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14 changes: 14 additions & 0 deletions clang/test/SemaCXX/warn-unused-private-field.cpp
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Expand Up @@ -20,6 +20,20 @@ class SpaceShipDefaultCompare {
int operator<=>(const SpaceShipDefaultCompare &) const = default;
};

class EqDefaultCompareOutOfClass {
int used; // no warning
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Please explain a touch better with 'no warning'? Something like, "Test to ensure that the defaulted operator results in this being seen as 'used' despite there not being code to do so."?

bool operator==(const EqDefaultCompareOutOfClass &) const;
};

bool EqDefaultCompareOutOfClass::operator==(const EqDefaultCompareOutOfClass &) const = default;

class FriendEqDefaultCompareOutOfClass {
int used; // no warning
friend bool operator==(const FriendEqDefaultCompareOutOfClass &, const FriendEqDefaultCompareOutOfClass &);
};

bool operator==(const FriendEqDefaultCompareOutOfClass &, const FriendEqDefaultCompareOutOfClass &) = default;

#endif

class NotFullyDefined {
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