Fix flag registry order

src/libexpr/primops/flake.cc

@@ -146,7 +146,7 @@ std::shared_ptr<FlakeRegistry> getFlagRegistry()
     return std::make_shared<FlakeRegistry>();
 }
 
-// This always returns a vector with flakeRef, userReg, globalReg.
+// This always returns a vector with flakeReg, userReg, globalReg.
 // If one of them doesn't exist, the registry is left empty but does exist.
 const Registries EvalState::getFlakeRegistries()
 {

src/libexpr/primops/flake.hh

@@ -5,6 +5,10 @@
 
 namespace nix {
 
+static const size_t FLAG_REGISTRY = 0;
+static const size_t USER_REGISTRY = 1;
+static const size_t GLOBAL_REGISTRY = 2;
+
 struct Value;
 class EvalState;