From ffc18583b1a086849ac0efd17da40ff510299b52 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 12 Jul 2020 22:15:14 +0000
Subject: [PATCH] Move C++17 "pattern matching" boilerplat to utils.hh

---
 src/libstore/content-address.cc | 4 ----
 src/libstore/derivations.cc     | 4 ----
 src/libstore/store-api.cc       | 4 ----
 src/libutil/util.hh             | 5 +++++
 4 files changed, 5 insertions(+), 12 deletions(-)

diff --git a/src/libstore/content-address.cc b/src/libstore/content-address.cc
index 6cb69d0a9..f45f77d5c 100644
--- a/src/libstore/content-address.cc
+++ b/src/libstore/content-address.cc
@@ -24,10 +24,6 @@ std::string makeFixedOutputCA(FileIngestionMethod method, const Hash & hash)
         + hash.to_string(Base32, true);
 }
 
-// FIXME Put this somewhere?
-template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
-template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
-
 std::string renderContentAddress(ContentAddress ca) {
     return std::visit(overloaded {
         [](TextHash th) {
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index d267468af..ce2025933 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -8,10 +8,6 @@
 
 namespace nix {
 
-// FIXME Put this somewhere?
-template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
-template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
-
 StorePath DerivationOutput::path(const Store & store, std::string_view drvName) const
 {
     return std::visit(overloaded {
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index 8d46bb436..62514d3be 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -802,10 +802,6 @@ void ValidPathInfo::sign(const Store & store, const SecretKey & secretKey)
     sigs.insert(secretKey.signDetached(fingerprint(store)));
 }
 
-// FIXME Put this somewhere?
-template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
-template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
-
 bool ValidPathInfo::isContentAddressed(const Store & store) const
 {
     if (! ca) return false;
diff --git a/src/libutil/util.hh b/src/libutil/util.hh
index 3641daaec..d38657843 100644
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@@ -597,4 +597,9 @@ constexpr auto enumerate(T && iterable)
 }
 
 
+// C++17 std::visit boilerplate
+template<class... Ts> struct overloaded : Ts... { using Ts::operator()...; };
+template<class... Ts> overloaded(Ts...) -> overloaded<Ts...>;
+
+
 }