FilterKey: fix ambiguous relational operators in C++20

The member operators weren't const, leading them to be ambiguous with
their reversed versions.

Fix by adding a private equals() function (to avoid churning the
implementation) and making the relational operators hidden friends.

Pick-to: 6.4 6.3 6.2 5.15
Task-number: QTBUG-104172
Change-Id: I97e74ef26fc2712d6f97c8f7d7bd61d6a625b42e
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>

2 files changed, 8 insertions, 8 deletions

diff --git a/src/render/materialsystem/filterkey.cpp b/src/render/materialsystem/filterkey.cpp
index 2a3a4d9d0..7429735ef 100644
--- a/src/render/materialsystem/filterkey.cpp
+++ b/src/render/materialsystem/filterkey.cpp
@@ -47,7 +47,7 @@ void FilterKey::syncFromFrontEnd(const QNode *frontEnd, bool firstTime)
     }
 }
 
-bool FilterKey::operator ==(const FilterKey &other)
+bool FilterKey::equals(const FilterKey &other) const
 {
     if (&other == this)
         return true;
@@ -65,11 +65,6 @@ bool FilterKey::operator ==(const FilterKey &other)
             other.value() == value());
 }
 
-bool FilterKey::operator !=(const FilterKey &other)
-{
-    return !operator ==(other);
-}
-
 } // namespace Render
 } // namespace Qt3DRender
 
diff --git a/src/render/materialsystem/filterkey_p.h b/src/render/materialsystem/filterkey_p.h
index bb27c8ced..e8bbf1b9d 100644
--- a/src/render/materialsystem/filterkey_p.h
+++ b/src/render/materialsystem/filterkey_p.h
@@ -36,10 +36,15 @@ public:
     const QVariant &value() const { return m_value; }
     const QString &name() const { return m_name; }
     void syncFromFrontEnd(const Qt3DCore::QNode *frontEnd, bool firstTime) override;
-    bool operator ==(const FilterKey &other);
-    bool operator !=(const FilterKey &other);
+
+    friend bool operator==(const FilterKey &lhs, const FilterKey &rhs)
+    { return lhs.equals(rhs); }
+    friend bool operator !=(const FilterKey &lhs, const FilterKey &rhs)
+    { return !lhs.equals(rhs); }
 
 private:
+    bool equals(const FilterKey &other) const;
+
     QVariant m_value;
     QString m_name;
 };