Everywhere: Remove redundant inequality comparison operators

C++20 can automatically synthesize `operator!=` from `operator==`, so
there is no point in writing such functions by hand if all they do is
call through to `operator==`.

This fixes a compile error with compilers that implement P2468 (Clang
16 currently). This paper restores the C++17 behavior that if both
`T::operator==(U)` and `T::operator!=(U)` exist, `U == T` won't be
rewritten in reverse to call `T::operator==(U)`. Removing `!=` operators
makes the rewriting possible again.
See https://reviews.llvm.org/D134529#3853062

Userland/Libraries/LibDebug/DebugInfo.h

@@ -50,7 +50,6 @@ public:
         }
 
         bool operator==(SourcePosition const& other) const { return file_path == other.file_path && line_number == other.line_number; }
-        bool operator!=(SourcePosition const& other) const { return !(*this == other); }
 
         static SourcePosition from_line_info(Dwarf::LineProgram::LineInfo const&);
     };

Userland/Libraries/LibDeviceTree/FlattenedDeviceTree.h

@@ -34,7 +34,6 @@ struct FlattenedDeviceTreeReserveEntry {
     BigEndian<u64> size;
 
     bool operator==(FlattenedDeviceTreeReserveEntry const& other) const { return other.address == address && other.size == size; }
-    bool operator!=(FlattenedDeviceTreeReserveEntry const& other) const { return !(operator==(other)); }
 };
 static_assert(sizeof(FlattenedDeviceTreeReserveEntry) == 16, "FDT Memory Reservation entry size must match specification");
 

Userland/Libraries/LibGUI/ModelIndex.h

@@ -33,11 +33,6 @@ public:
         return m_model == other.m_model && m_row == other.m_row && m_column == other.m_column && m_internal_data == other.m_internal_data;
     }
 
-    bool operator!=(ModelIndex const& other) const
-    {
-        return !(*this == other);
-    }
-
     Model const* model() const { return m_model; }
 
     Variant data(ModelRole = ModelRole::Display) const;

Userland/Libraries/LibGfx/Color.h

@@ -350,11 +350,6 @@ public:
         return m_value == other.m_value;
     }
 
-    constexpr bool operator!=(Color const& other) const
-    {
-        return m_value != other.m_value;
-    }
-
     String to_string() const;
     String to_string_without_alpha() const;
     static Optional<Color> from_string(StringView);

Userland/Libraries/LibGfx/Point.h

@@ -132,12 +132,6 @@ public:
         return x() == other.x() && y() == other.y();
     }
 
-    template<class U>
-    [[nodiscard]] bool operator!=(Point<U> const& other) const
-    {
-        return !(*this == other);
-    }
-
     [[nodiscard]] Point<T> operator+(Point<T> const& other) const { return { m_x + other.m_x, m_y + other.m_y }; }
 
     Point<T>& operator+=(Point<T> const& other)

Userland/Libraries/LibGfx/Rect.h

@@ -477,12 +477,6 @@ public:
         return location() == other.location() && size() == other.size();
     }
 
-    template<class U>
-    [[nodiscard]] bool operator!=(Rect<U> const& other) const
-    {
-        return !(*this == other);
-    }
-
     [[nodiscard]] Rect<T> operator*(T factor) const { return { m_location * factor, m_size * factor }; }
 
     Rect<T>& operator*=(T factor)

Userland/Libraries/LibGfx/Size.h

@@ -99,12 +99,6 @@ public:
         return width() == other.width() && height() == other.height();
     }
 
-    template<class U>
-    [[nodiscard]] constexpr bool operator!=(Size<U> const& other) const
-    {
-        return !(*this == other);
-    }
-
     constexpr Size<T>& operator-=(Size<T> const& other)
     {
         m_width -= other.m_width;

Userland/Libraries/LibJS/Runtime/PropertyAttributes.h

@@ -59,7 +59,6 @@ public:
     }
 
     bool operator==(PropertyAttributes const& other) const { return m_bits == other.m_bits; }
-    bool operator!=(PropertyAttributes const& other) const { return m_bits != other.m_bits; }
 
     [[nodiscard]] u8 bits() const { return m_bits; }
 

Userland/Libraries/LibLine/KeyCallbackMachine.h

@@ -38,11 +38,6 @@ struct Key {
     {
         return other.key == key && other.modifiers == modifiers;
     }
-
-    bool operator!=(Key const& other) const
-    {
-        return !(*this == other);
-    }
 };
 
 struct KeyCallback {

Userland/Libraries/LibRegex/RegexMatch.h

@@ -310,11 +310,6 @@ public:
             [&](StringView view) { return view == cstring; });
     }
 
-    bool operator!=(char const* cstring) const
-    {
-        return !(*this == cstring);
-    }
-
     bool operator==(String const& string) const
     {
         return m_view.visit(
@@ -333,11 +328,6 @@ public:
             [&](StringView view) { return view == string; });
     }
 
-    bool operator!=(StringView other) const
-    {
-        return !(*this == other);
-    }
-
     bool operator==(Utf32View const& other) const
     {
         return m_view.visit(
@@ -349,11 +339,6 @@ public:
             [&](StringView view) { return view == RegexStringView { other }.to_string(); });
     }
 
-    bool operator!=(Utf32View const& other) const
-    {
-        return !(*this == other);
-    }
-
     bool operator==(Utf16View const& other) const
     {
         return m_view.visit(
@@ -363,11 +348,6 @@ public:
             [&](StringView view) { return view == RegexStringView { other }.to_string(); });
     }
 
-    bool operator!=(Utf16View const& other) const
-    {
-        return !(*this == other);
-    }
-
     bool operator==(Utf8View const& other) const
     {
         return m_view.visit(
@@ -377,11 +357,6 @@ public:
             [&](StringView view) { return other.as_string() == view; });
     }
 
-    bool operator!=(Utf8View const& other) const
-    {
-        return !(*this == other);
-    }
-
     bool equals(RegexStringView other) const
     {
         return other.m_view.visit([this](auto const& view) { return operator==(view); });

Userland/Libraries/LibSQL/HashIndex.h

@@ -118,9 +118,7 @@ public:
     [[nodiscard]] bool is_end() const { return !m_current; }
 
     bool operator==(HashIndexIterator const& other) const;
-    bool operator!=(HashIndexIterator const& other) const { return !(*this == other); }
     bool operator==(Key const& other) const;
-    bool operator!=(Key const& other) const { return !(*this == other); }
 
     HashIndexIterator operator++()
     {

Userland/Libraries/LibVT/Attribute.h

@@ -63,10 +63,6 @@ struct Attribute {
     {
         return foreground_color == other.foreground_color && background_color == other.background_color && flags == other.flags;
     }
-    constexpr bool operator!=(Attribute const& other) const
-    {
-        return !(*this == other);
-    }
 };
 
 }

Userland/Libraries/LibWeb/CSS/Angle.h

@@ -43,11 +43,6 @@ public:
         return m_type == other.m_type && m_value == other.m_value;
     }
 
-    bool operator!=(Angle const& other) const
-    {
-        return !(*this == other);
-    }
-
 private:
     StringView unit_name() const;
 

Userland/Libraries/LibWeb/CSS/Display.h

@@ -35,8 +35,6 @@ public:
         VERIFY_NOT_REACHED();
     }
 
-    bool operator!=(Display const& other) const { return !(*this == other); }
-
     enum class Outside {
         Block,
         Inline,

Userland/Libraries/LibWeb/CSS/Frequency.h

@@ -40,11 +40,6 @@ public:
         return m_type == other.m_type && m_value == other.m_value;
     }
 
-    bool operator!=(Frequency const& other) const
-    {
-        return !(*this == other);
-    }
-
 private:
     StringView unit_name() const;
 

Userland/Libraries/LibWeb/CSS/Length.h

@@ -121,10 +121,6 @@ public:
     // We have a RefPtr<CalculatedStyleValue> member, but can't include the header StyleValue.h as it includes
     // this file already. To break the cyclic dependency, we must move all method definitions out.
     bool operator==(Length const& other) const;
-    bool operator!=(Length const& other) const
-    {
-        return !(*this == other);
-    }
 
     float relative_length_to_px(Gfx::IntRect const& viewport_rect, Gfx::FontPixelMetrics const& font_metrics, float font_size, float root_font_size) const;
 

Userland/Libraries/LibWeb/CSS/Percentage.h

@@ -37,7 +37,6 @@ public:
     }
 
     bool operator==(Percentage const& other) const { return m_value == other.m_value; }
-    bool operator!=(Percentage const& other) const { return !(*this == other); }
 
 private:
     float m_value;
@@ -147,7 +146,6 @@ public:
             return (m_value.template get<Percentage>() == other.m_value.template get<Percentage>());
         return (m_value.template get<T>() == other.m_value.template get<T>());
     }
-    bool operator!=(PercentageOr<T> const& other) const { return !(*this == other); }
 
 protected:
     bool is_t() const { return m_value.template has<T>(); }

Userland/Libraries/LibWeb/CSS/Resolution.h

@@ -32,11 +32,6 @@ public:
         return m_type == other.m_type && m_value == other.m_value;
     }
 
-    bool operator!=(Resolution const& other) const
-    {
-        return !(*this == other);
-    }
-
 private:
     StringView unit_name() const;
 

Userland/Libraries/LibWeb/CSS/StyleProperties.h

@@ -109,7 +109,6 @@ public:
     float line_height(Layout::Node const&) const;
 
     bool operator==(StyleProperties const&) const;
-    bool operator!=(StyleProperties const& other) const { return !(*this == other); }
 
     Optional<CSS::Position> position() const;
     Optional<int> z_index() const;

Userland/Libraries/LibWeb/CSS/StyleValue.h

@@ -402,7 +402,6 @@ public:
     virtual String to_string() const = 0;
 
     bool operator==(StyleValue const& other) const { return equals(other); }
-    bool operator!=(StyleValue const& other) const { return !(*this == other); }
 
     virtual bool equals(StyleValue const& other) const = 0;
 

Userland/Libraries/LibWeb/CSS/Time.h

@@ -41,11 +41,6 @@ public:
         return m_type == other.m_type && m_value == other.m_value;
     }
 
-    bool operator!=(Time const& other) const
-    {
-        return !(*this == other);
-    }
-
 private:
     StringView unit_name() const;
 

Userland/Libraries/LibWeb/DOM/Position.h

@@ -35,11 +35,6 @@ public:
         return m_node.ptr() == other.m_node.ptr() && m_offset == other.m_offset;
     }
 
-    bool operator!=(Position const& other) const
-    {
-        return !(*this == other);
-    }
-
     String to_string() const;
 
 private:

Userland/Libraries/LibWeb/HTML/Origin.h

@@ -106,7 +106,6 @@ public:
     }
 
     bool operator==(Origin const& other) const { return is_same_origin(other); }
-    bool operator!=(Origin const& other) const { return !is_same_origin(other); }
 
 private:
     String m_scheme;