From f0b484892ce6e09cf79c858460c96d3540dba1a8 Mon Sep 17 00:00:00 2001
From: Tyler Veness <calcmogul@gmail.com>
Date: Tue, 12 Oct 2021 23:28:26 -0700
Subject: [PATCH] [wpiutil] Fix StringMap iterator equality check (#3629)

This fixes the following warning.
The member function operator== only works in C++17, and the friend operator== only works in C++20.

```
 /Users/runner/.gradle/caches/transforms-2/files-2.1/c671f5a5dff922b8870f4eb33f4c8e2a/wpiutil-cpp-2022.1.1-alpha-3-1-g4e3fd7d-headers/wpi/json.h:1847:46: warning: ISO C++20 considers use of overloaded operator '==' (with operand types 'const typename json::object_t::iterator' (aka 'const StringMapIterator<wpi::json>') and 'const typename json::object_t::iterator') to be ambiguous despite there being a unique best viable function [-Wambiguous-reversed-operator]
                return (m_it.object_iterator == other.m_it.object_iterator);
                        ~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/runner/.gradle/caches/transforms-2/files-2.1/c671f5a5dff922b8870f4eb33f4c8e2a/wpiutil-cpp-2022.1.1-alpha-3-1-g4e3fd7d-headers/wpi/json.h:1863:20: note: in instantiation of member function 'wpi::detail::iter_impl<const wpi::json>::operator==' requested here
        return not operator==(other);
                   ^
/Users/runner/.gradle/caches/transforms-2/files-2.1/c671f5a5dff922b8870f4eb33f4c8e2a/wpiutil-cpp-2022.1.1-alpha-3-1-g4e3fd7d-headers/wpi/json.h:5008:20: note: in instantiation of member function 'wpi::detail::iter_impl<const wpi::json>::operator!=' requested here
            if (it != end())
                   ^
/Users/runner/.gradle/caches/transforms-2/files-2.1/c671f5a5dff922b8870f4eb33f4c8e2a/wpiutil-cpp-2022.1.1-alpha-3-1-g4e3fd7d-headers/wpi/json.h:5025:16: note: in instantiation of function template specialization 'wpi::json::value<std::basic_string<char>, 0>' requested here
        return value(key, std::string(default_value));
               ^
/Users/runner/.gradle/caches/transforms-2/files-2.1/c671f5a5dff922b8870f4eb33f4c8e2a/wpiutil-cpp-2022.1.1-alpha-3-1-g4e3fd7d-headers/wpi/StringMap.h:442:8: note: ambiguity is between a regular call to this operator and a call with the argument order reversed
  bool operator==(const DerivedTy &RHS) const { return Ptr == RHS.Ptr; }
       ^
```
---
 wpiutil/src/main/native/include/wpi/StringMap.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/wpiutil/src/main/native/include/wpi/StringMap.h b/wpiutil/src/main/native/include/wpi/StringMap.h
index 0800efb020..dac2f20914 100644
--- a/wpiutil/src/main/native/include/wpi/StringMap.h
+++ b/wpiutil/src/main/native/include/wpi/StringMap.h
@@ -439,7 +439,13 @@ public:
     return static_cast<DerivedTy &>(*this);
   }
 
+#if __cplusplus < 202002L
   bool operator==(const DerivedTy &RHS) const { return Ptr == RHS.Ptr; }
+#else
+  friend bool operator==(const DerivedTy &LHS, const DerivedTy &RHS) {
+    return LHS.Ptr == RHS.Ptr;
+  }
+#endif
 
   DerivedTy &operator++() { // Preincrement
     ++Ptr;