From e8439c1c9ddc02e8f3aa9726cd765637b34d68fb Mon Sep 17 00:00:00 2001
From: smikims <smikims.me@gmail.com>
Date: Tue, 25 Jan 2022 06:07:40 -0800
Subject: [PATCH] Avoid infinite recursion in comparison operators on
 SmallVector (#4681)

C++20 automatically adds reversed versions of operator overloads for
consideration; in this particular instance this results in infinite
recursion, which has now been pointed out elsewhere as a known issue
when migrating to C++20. Here we just disable one of the overloads in
C++20 mode and let the auto-reversing take care of it for us.
---
 source/util/small_vector.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/source/util/small_vector.h b/source/util/small_vector.h
index f2c1147b..8f56268a 100644
--- a/source/util/small_vector.h
+++ b/source/util/small_vector.h
@@ -175,9 +175,12 @@ class SmallVector {
     return true;
   }
 
+// Avoid infinite recursion from rewritten operators in C++20
+#if __cplusplus <= 201703L
   friend bool operator==(const std::vector<T>& lhs, const SmallVector& rhs) {
     return rhs == lhs;
   }
+#endif
 
   friend bool operator!=(const SmallVector& lhs, const std::vector<T>& rhs) {
     return !(lhs == rhs);