refactor: Remove operator!= overloads that C++20 synthesizes (#7994)

include/xrpl/basics/Buffer.h

@@ -226,10 +226,4 @@ operator==(Buffer const& lhs, Buffer const& rhs) noexcept
     return std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
 }
 
-inline bool
-operator!=(Buffer const& lhs, Buffer const& rhs) noexcept
-{
-    return !(lhs == rhs);
-}
-
 }  // namespace xrpl

include/xrpl/basics/IntrusivePointer.h

@@ -96,9 +96,6 @@ public:
     SharedIntrusive&
     operator=(SharedIntrusive const& rhs);
 
-    bool
-    operator!=(std::nullptr_t) const;
-
     bool
     operator==(std::nullptr_t) const;
 

include/xrpl/basics/IntrusivePointer.ipp

@@ -111,13 +111,6 @@ SharedIntrusive<T>::operator=(SharedIntrusive<TT>&& rhs)
     return *this;
 }
 
-template <class T>
-bool
-SharedIntrusive<T>::operator!=(std::nullptr_t) const
-{
-    return this->get() != nullptr;
-}
-
 template <class T>
 bool
 SharedIntrusive<T>::operator==(std::nullptr_t) const

include/xrpl/basics/Number.h

@@ -449,12 +449,6 @@ public:
             x.exponent_ == y.exponent_;
     }
 
-    friend constexpr bool
-    operator!=(Number const& x, Number const& y) noexcept
-    {
-        return !(x == y);
-    }
-
     friend constexpr bool
     operator<(Number const& l, Number const& r) noexcept
     {

include/xrpl/basics/SHAMapHash.h

@@ -85,12 +85,6 @@ public:
     }
 };
 
-inline bool
-operator!=(SHAMapHash const& x, SHAMapHash const& y)
-{
-    return !(x == y);
-}
-
 template <>
 inline std::size_t
 extract(SHAMapHash const& key)

include/xrpl/basics/Slice.h

@@ -208,12 +208,6 @@ operator==(Slice const& lhs, Slice const& rhs) noexcept
     return std::memcmp(lhs.data(), rhs.data(), lhs.size()) == 0;
 }
 
-inline bool
-operator!=(Slice const& lhs, Slice const& rhs) noexcept
-{
-    return !(lhs == rhs);
-}
-
 inline bool
 operator<(Slice const& lhs, Slice const& rhs) noexcept
 {

include/xrpl/basics/partitioned_unordered_map.h

@@ -116,12 +116,6 @@ public:
         {
             return lhs.map == rhs.map && lhs.ait == rhs.ait && lhs.mit == rhs.mit;
         }
-
-        friend bool
-        operator!=(Iterator const& lhs, Iterator const& rhs)
-        {
-            return !(lhs == rhs);
-        }
     };
 
     struct ConstIterator
@@ -189,12 +183,6 @@ public:
         {
             return lhs.map == rhs.map && lhs.ait == rhs.ait && lhs.mit == rhs.mit;
         }
-
-        friend bool
-        operator!=(ConstIterator const& lhs, ConstIterator const& rhs)
-        {
-            return !(lhs == rhs);
-        }
     };
 
 private:

include/xrpl/beast/container/detail/aged_ordered_container.h

@@ -1038,25 +1038,6 @@ public:
                Compare,
                OtherAllocator> const& other) const;
 
-    template <
-        bool OtherIsMulti,
-        bool OtherIsMap,
-        class OtherT,
-        class OtherDuration,
-        class OtherAllocator>
-    bool
-    operator!=(AgedOrderedContainer<
-               OtherIsMulti,
-               OtherIsMap,
-               Key,
-               OtherT,
-               OtherDuration,
-               Compare,
-               OtherAllocator> const& other) const
-    {
-        return !(this->operator==(other));
-    }
-
     template <
         bool OtherIsMulti,
         bool OtherIsMap,

include/xrpl/beast/container/detail/aged_unordered_container.h

@@ -1340,28 +1340,6 @@ public:
                OtherAllocator> const& other) const
         requires MaybeMulti;
 
-    template <
-        bool OtherIsMulti,
-        bool OtherIsMap,
-        class OtherKey,
-        class OtherT,
-        class OtherDuration,
-        class OtherHash,
-        class OtherAllocator>
-    bool
-    operator!=(AgedUnorderedContainer<
-               OtherIsMulti,
-               OtherIsMap,
-               OtherKey,
-               OtherT,
-               OtherDuration,
-               OtherHash,
-               KeyEqual,
-               OtherAllocator> const& other) const
-    {
-        return !(this->operator==(other));
-    }
-
 private:
     bool
     wouldExceed(size_type additional) const

include/xrpl/beast/core/List.h

@@ -82,13 +82,6 @@ public:
         return node_ == other.node_;
     }
 
-    template <typename M>
-    bool
-    operator!=(ListIterator<M> const& other) const noexcept
-    {
-        return !((*this) == other);
-    }
-
     reference
     operator*() const noexcept
     {

include/xrpl/beast/net/IPEndpoint.h

@@ -110,12 +110,6 @@ public:
     operator==(Endpoint const& lhs, Endpoint const& rhs);
     friend bool
     operator<(Endpoint const& lhs, Endpoint const& rhs);
-
-    friend bool
-    operator!=(Endpoint const& lhs, Endpoint const& rhs)
-    {
-        return !(lhs == rhs);
-    }
     friend bool
     operator>(Endpoint const& lhs, Endpoint const& rhs)
     {

include/xrpl/beast/rfc2616.h

@@ -229,12 +229,6 @@ public:
         return other.it_ == it_ && other.end_ == end_ && other.value_.size() == value_.size();
     }
 
-    bool
-    operator!=(ListIterator const& other) const
-    {
-        return !(*this == other);
-    }
-
     reference
     operator*() const
     {

include/xrpl/conditions/Condition.h

@@ -92,10 +92,4 @@ operator==(Condition const& lhs, Condition const& rhs)
         lhs.fingerprint == rhs.fingerprint;
 }
 
-inline bool
-operator!=(Condition const& lhs, Condition const& rhs)
-{
-    return !(lhs == rhs);
-}
-
 }  // namespace xrpl::cryptoconditions

include/xrpl/conditions/Fulfillment.h

@@ -93,12 +93,6 @@ operator==(Fulfillment const& lhs, Fulfillment const& rhs)
         lhs.fingerprint() == rhs.fingerprint();
 }
 
-inline bool
-operator!=(Fulfillment const& lhs, Fulfillment const& rhs)
-{
-    return !(lhs == rhs);
-}
-
 /**
  * Determine whether the given fulfillment and condition match
  */

include/xrpl/json/json_value.h

@@ -72,36 +72,18 @@ operator==(StaticString x, StaticString y)
     return strcmp(x.cStr(), y.cStr()) == 0;
 }
 
-inline bool
-operator!=(StaticString x, StaticString y)
-{
-    return !(x == y);
-}
-
 inline bool
 operator==(std::string const& x, StaticString y)
 {
     return strcmp(x.c_str(), y.cStr()) == 0;
 }
 
-inline bool
-operator!=(std::string const& x, StaticString y)
-{
-    return !(x == y);
-}
-
 inline bool
 operator==(StaticString x, std::string const& y)
 {
     return y == x;
 }
 
-inline bool
-operator!=(StaticString x, std::string const& y)
-{
-    return !(y == x);
-}
-
 /**
  * @brief Represents a <a HREF="http://www.json.org">JSON</a> value.
  *
@@ -489,12 +471,6 @@ toJson(xrpl::Number const& number)
 bool
 operator==(Value const&, Value const&);
 
-inline bool
-operator!=(Value const& x, Value const& y)
-{
-    return !(x == y);
-}
-
 bool
 operator<(Value const&, Value const&);
 
@@ -562,12 +538,6 @@ public:
         return isEqual(other);
     }
 
-    bool
-    operator!=(SelfType const& other) const
-    {
-        return !isEqual(other);
-    }
-
     /**
      * Return either the index or the member name of the referenced value as a
      * Value.

include/xrpl/ledger/BookDirs.h

@@ -49,12 +49,6 @@ public:
     bool
     operator==(const_iterator const& other) const;
 
-    bool
-    operator!=(const_iterator const& other) const
-    {
-        return !(*this == other);
-    }
-
     reference
     operator*() const;
 

include/xrpl/ledger/CanonicalTXSet.h

@@ -59,12 +59,6 @@ private:
             return lhs.txId_ == rhs.txId_;
         }
 
-        friend bool
-        operator!=(Key const& lhs, Key const& rhs)
-        {
-            return !(lhs == rhs);
-        }
-
         [[nodiscard]] uint256 const&
         getAccount() const
         {

include/xrpl/ledger/Dir.h

@@ -59,12 +59,6 @@ public:
     bool
     operator==(ConstIterator const& other) const;
 
-    bool
-    operator!=(ConstIterator const& other) const
-    {
-        return !(*this == other);
-    }
-
     reference
     operator*() const;
 

include/xrpl/ledger/detail/ReadViewFwdRange.h

@@ -85,9 +85,6 @@ public:
         bool
         operator==(Iterator const& other) const;
 
-        bool
-        operator!=(Iterator const& other) const;
-
         // Can throw
         reference
         operator*() const;

include/xrpl/ledger/detail/ReadViewFwdRange.ipp

@@ -64,13 +64,6 @@ ReadViewFwdRange<ValueType>::Iterator::operator==(Iterator const& other) const
     return impl_ == other.impl_;
 }
 
-template <class ValueType>
-bool
-ReadViewFwdRange<ValueType>::Iterator::operator!=(Iterator const& other) const
-{
-    return !(*this == other);
-}
-
 template <class ValueType>
 auto
 ReadViewFwdRange<ValueType>::Iterator::operator*() const -> reference

include/xrpl/protocol/Quality.h

@@ -75,13 +75,6 @@ operator==(TAmounts<In, Out> const& lhs, TAmounts<In, Out> const& rhs) noexcept
     return lhs.in == rhs.in && lhs.out == rhs.out;
 }
 
-template <class In, class Out>
-bool
-operator!=(TAmounts<In, Out> const& lhs, TAmounts<In, Out> const& rhs) noexcept
-{
-    return !(lhs == rhs);
-}
-
 //------------------------------------------------------------------------------
 
 // XRPL specific constant used for parsing qualities and other things
@@ -271,12 +264,6 @@ public:
         return lhs.value_ == rhs.value_;
     }
 
-    friend bool
-    operator!=(Quality const& lhs, Quality const& rhs) noexcept
-    {
-        return !(lhs == rhs);
-    }
-
     friend std::ostream&
     operator<<(std::ostream& os, Quality const& quality)
     {

include/xrpl/protocol/Rules.h

@@ -98,9 +98,6 @@ public:
      */
     bool
     operator==(Rules const&) const;
-
-    bool
-    operator!=(Rules const& other) const;
 };
 
 std::optional<Rules> const&

include/xrpl/protocol/STAmount.h

@@ -642,12 +642,6 @@ operator==(STAmount const& lhs, STAmount const& rhs);
 bool
 operator<(STAmount const& lhs, STAmount const& rhs);
 
-inline bool
-operator!=(STAmount const& lhs, STAmount const& rhs)
-{
-    return !(lhs == rhs);
-}
-
 inline bool
 operator>(STAmount const& lhs, STAmount const& rhs)
 {

include/xrpl/protocol/STArray.h

@@ -133,9 +133,6 @@ public:
     bool
     operator==(STArray const& s) const;
 
-    bool
-    operator!=(STArray const& s) const;
-
     iterator
     erase(iterator pos);
 
@@ -283,12 +280,6 @@ STArray::operator==(STArray const& s) const
     return v_ == s.v_;
 }
 
-inline bool
-STArray::operator!=(STArray const& s) const
-{
-    return v_ != s.v_;
-}
-
 inline STArray::iterator
 STArray::erase(iterator pos)
 {

include/xrpl/protocol/STBase.h

@@ -140,8 +140,6 @@ public:
 
     bool
     operator==(STBase const& t) const;
-    bool
-    operator!=(STBase const& t) const;
 
     template <class D>
     D&

include/xrpl/protocol/STCurrency.h

@@ -93,12 +93,6 @@ operator==(STCurrency const& lhs, STCurrency const& rhs)
     return lhs.currency() == rhs.currency();
 }
 
-inline bool
-operator!=(STCurrency const& lhs, STCurrency const& rhs)
-{
-    return !operator==(lhs, rhs);
-}
-
 inline bool
 operator<(STCurrency const& lhs, STCurrency const& rhs)
 {

include/xrpl/protocol/STObject.h

@@ -432,8 +432,6 @@ public:
 
     bool
     operator==(STObject const& o) const;
-    bool
-    operator!=(STObject const& o) const;
 
     class FieldErr;
 
@@ -667,36 +665,6 @@ public:
         return !lhs.engaged() || *lhs == *rhs;
     }
 
-    friend bool
-    operator!=(OptionalProxy const& lhs, std::nullopt_t) noexcept
-    {
-        return !(lhs == std::nullopt);
-    }
-
-    friend bool
-    operator!=(std::nullopt_t, OptionalProxy const& rhs) noexcept
-    {
-        return !(rhs == std::nullopt);
-    }
-
-    friend bool
-    operator!=(OptionalProxy const& lhs, optional_type const& rhs) noexcept
-    {
-        return !(lhs == rhs);
-    }
-
-    friend bool
-    operator!=(optional_type const& lhs, OptionalProxy const& rhs) noexcept
-    {
-        return !(lhs == rhs);
-    }
-
-    friend bool
-    operator!=(OptionalProxy const& lhs, OptionalProxy const& rhs) noexcept
-    {
-        return !(lhs == rhs);
-    }
-
     // Emulate std::optional::value_or
     [[nodiscard]] value_type
     valueOr(value_type val) const;
@@ -1202,12 +1170,6 @@ STObject::setFieldH160(SField const& field, BaseUInt<160, Tag> const& v)
     }
 }
 
-inline bool
-STObject::operator!=(STObject const& o) const
-{
-    return !(*this == o);
-}
-
 template <typename T, typename V>
 V
 STObject::getFieldByValue(SField const& field) const

include/xrpl/protocol/STPathSet.h

@@ -115,9 +115,6 @@ public:
     bool
     operator==(STPathElement const& t) const;
 
-    bool
-    operator!=(STPathElement const& t) const;
-
 private:
     static std::size_t
     getHash(STPathElement const& element);
@@ -432,12 +429,6 @@ STPathElement::operator==(STPathElement const& t) const
         accountID_ == t.accountID_ && assetID_ == t.assetID_ && issuerID_ == t.issuerID_;
 }
 
-inline bool
-STPathElement::operator!=(STPathElement const& t) const
-{
-    return !operator==(t);
-}
-
 // ------------ STPath ------------
 
 inline STPath::STPath(std::vector<STPathElement> p) : path_(std::move(p))

include/xrpl/protocol/SeqProxy.h

@@ -123,12 +123,6 @@ public:
         return (lhs.value() == rhs.value());
     }
 
-    friend constexpr bool
-    operator!=(SeqProxy lhs, SeqProxy rhs)
-    {
-        return !(lhs == rhs);
-    }
-
     friend constexpr bool
     operator<(SeqProxy lhs, SeqProxy rhs)
     {

include/xrpl/protocol/Serializer.h

@@ -265,20 +265,10 @@ public:
         return v == data_;
     }
     bool
-    operator!=(Blob const& v) const
-    {
-        return v != data_;
-    }
-    bool
     operator==(Serializer const& v) const
     {
         return v.data_ == data_;
     }
-    bool
-    operator!=(Serializer const& v) const
-    {
-        return v.data_ != data_;
-    }
 
     static int
     decodeLengthLength(int b1);

include/xrpl/protocol/Units.h

@@ -258,13 +258,6 @@ public:
         return value_ == other;
     }
 
-    template <Compatible<ValueUnit> Other>
-    constexpr bool
-    operator!=(ValueUnit<unit_type, Other> const& other) const
-    {
-        return !operator==(other);
-    }
-
     constexpr bool
     operator<(ValueUnit const& other) const
     {

include/xrpl/protocol/detail/STVar.h

@@ -152,10 +152,4 @@ operator==(STVar const& lhs, STVar const& rhs)
     return lhs.get().isEquivalent(rhs.get());
 }
 
-inline bool
-operator!=(STVar const& lhs, STVar const& rhs)
-{
-    return !(lhs == rhs);
-}
-
 }  // namespace xrpl::detail

include/xrpl/server/Manifest.h

@@ -306,12 +306,6 @@ operator==(Manifest const& lhs, Manifest const& rhs)
         lhs.serialized == rhs.serialized;
 }
 
-inline bool
-operator!=(Manifest const& lhs, Manifest const& rhs)
-{
-    return !(lhs == rhs);
-}
-
 struct ValidatorToken
 {
     std::string manifest;

include/xrpl/shamap/SHAMap.h

@@ -789,12 +789,6 @@ operator==(SHAMap::ConstIterator const& x, SHAMap::ConstIterator const& y)
     return x.item_ == y.item_;
 }
 
-inline bool
-operator!=(SHAMap::ConstIterator const& x, SHAMap::ConstIterator const& y)
-{
-    return !(x == y);
-}
-
 inline SHAMap::ConstIterator
 SHAMap::begin() const
 {

include/xrpl/shamap/SHAMapNodeID.h

@@ -3,6 +3,7 @@
 #include <xrpl/basics/CountedObject.h>
 #include <xrpl/basics/base_uint.h>
 
+#include <compare>
 #include <cstddef>
 #include <optional>
 #include <ostream>
@@ -65,45 +66,32 @@ public:
     static SHAMapNodeID
     createID(int depth, uint256 const& key);
 
-    // FIXME-C++20: use spaceship and operator synthesis
     /**
      * Comparison operators
+     *
+     * <, >, <= and >= are synthesized from the spaceship. It is written out
+     * rather than defaulted because the ordering is by depth first, and the
+     * members are not declared in that order.
      */
-    bool
-    operator<(SHAMapNodeID const& n) const
+    std::strong_ordering
+    operator<=>(SHAMapNodeID const& n) const
     {
-        return std::tie(depth_, id_) < std::tie(n.depth_, n.id_);
-    }
-
-    bool
-    operator>(SHAMapNodeID const& n) const
-    {
-        return n < *this;
-    }
-
-    bool
-    operator<=(SHAMapNodeID const& n) const
-    {
-        return !(n < *this);
-    }
-
-    bool
-    operator>=(SHAMapNodeID const& n) const
-    {
-        return !(*this < n);
+        return std::tie(depth_, id_) <=> std::tie(n.depth_, n.id_);
     }
 
+    /**
+     * Equality, which the spaceship above does not provide.
+     *
+     * Only a *defaulted* operator<=> implicitly declares a defaulted
+     * operator==; the one above is user-provided, so == has to be written.
+     * It cannot be defaulted either, because a defaulted == would also compare
+     * the CountedObject base, which is not equality comparable.
+     */
     bool
     operator==(SHAMapNodeID const& n) const
     {
         return (depth_ == n.depth_) && (id_ == n.id_);
     }
-
-    bool
-    operator!=(SHAMapNodeID const& n) const
-    {
-        return !(*this == n);
-    }
 };
 
 inline std::string

include/xrpl/tx/paths/detail/Steps.h

@@ -274,19 +274,6 @@ public:
         return lhs.equal(rhs);
     }
 
-    /**
-     * Return true if lhs != rhs.
-     *
-     * @param lhs Step to compare.
-     * @param rhs Step to compare.
-     * @return true if lhs != rhs.
-     */
-    friend bool
-    operator!=(Step const& lhs, Step const& rhs)
-    {
-        return !(lhs == rhs);
-    }
-
     /**
      * Streaming operator for a Step.
      */

src/libxrpl/protocol/Rules.cpp

@@ -193,12 +193,6 @@ Rules::operator==(Rules const& other) const
     return *impl_ == *other.impl_;
 }
 
-bool
-Rules::operator!=(Rules const& other) const
-{
-    return !(*this == other);
-}
-
 bool
 isFeatureEnabled(uint256 const& feature, bool resultIfNoRules)
 {

src/libxrpl/protocol/STBase.cpp

@@ -38,12 +38,6 @@ STBase::operator==(STBase const& t) const
     return (getSType() == t.getSType()) && isEquivalent(t);
 }
 
-bool
-STBase::operator!=(STBase const& t) const
-{
-    return (getSType() != t.getSType()) || !isEquivalent(t);
-}
-
 STBase*
 STBase::copy(std::size_t n, void* buf) const
 {

src/test/jtx/amount.h

@@ -162,12 +162,6 @@ operator==(PrettyAmount const& lhs, PrettyAmount const& rhs)
     return lhs.value() == rhs.value();
 }
 
-inline bool
-operator!=(PrettyAmount const& lhs, PrettyAmount const& rhs)
-{
-    return !operator==(lhs, rhs);
-}
-
 std::ostream&
 operator<<(std::ostream& os, PrettyAmount const& amount);