libutil: Optimize feature checks

Instead of doing a linear search on an std::set, we use a bitset enum.

Change-Id: Ide537f6cffdd16d06e59aaeb2e4ac0acb6493421

1 files changed, 4 insertions, 5 deletions

diff --git a/src/nix/main.cc b/src/nix/main.cc
index 5356a0d04..e84e4f310 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -378,11 +378,10 @@ void mainWrapped(int argc, char * * argv)
     }
 
     if (argc == 2 && std::string(argv[1]) == "__dump-language") {
-        experimentalFeatureSettings.experimentalFeatures = {
-            Xp::Flakes,
-            Xp::FetchClosure,
-            Xp::DynamicDerivations,
-        };
+        experimentalFeatureSettings.experimentalFeatures = ExperimentalFeatures{}
+            | Xp::Flakes
+            | Xp::FetchClosure
+            | Xp::DynamicDerivations;
         evalSettings.pureEval = false;
         EvalState state({}, openStore("dummy://"));
         auto res = nlohmann::json::object();