From 550b3479cf066b9e5a435d1cb42240f88021b31f Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 15 Jul 2024 15:46:30 +0200
Subject: [PATCH] Include the accessor in the SourcePath hash

---
 src/libutil/source-path.hh |  6 +++++-
 src/libutil/util.hh        | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/libutil/source-path.hh b/src/libutil/source-path.hh
index 94174412787..d310231a7c9 100644
--- a/src/libutil/source-path.hh
+++ b/src/libutil/source-path.hh
@@ -9,6 +9,8 @@
 #include "canon-path.hh"
 #include "source-accessor.hh"
 
+#include <boost/functional/hash.hpp> // for boost::hash_combine
+
 namespace nix {
 
 /**
@@ -128,6 +130,8 @@ struct std::hash<nix::SourcePath>
 {
     std::size_t operator()(const nix::SourcePath & s) const noexcept
     {
-        return std::hash<decltype(s.path)>{}(s.path);
+        std::size_t hash = 0;
+        hash_combine(hash, s.accessor->number, s.path);
+        return hash;
     }
 };
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 23682ff7ca5..dd113984355 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -360,4 +360,18 @@ inline std::string operator + (std::string_view s1, const char * s2)
     return s;
 }
 
+/**
+ * hash_combine() from Boost. Hash several hashable values together
+ * into a single hash.
+ */
+inline void hash_combine(std::size_t & seed) { }
+
+template <typename T, typename... Rest>
+inline void hash_combine(std::size_t & seed, const T & v, Rest... rest)
+{
+    std::hash<T> hasher;
+    seed ^= hasher(v) + 0x9e3779b9 + (seed<<6) + (seed>>2);
+    hash_combine(seed, rest...);
+}
+
 }