7 files changed, 10 insertions, 9 deletions
diff --git a/third_party/nix/src/libexpr/common-eval-args.cc b/third_party/nix/src/libexpr/common-eval-args.cc
index 7a87841c9b77..33319cbabb17 100644
--- a/third_party/nix/src/libexpr/common-eval-args.cc
+++ b/third_party/nix/src/libexpr/common-eval-args.cc
@@ -29,7 +29,7 @@ MixEvalArgs::MixEvalArgs() {
           "add a path to the list of locations used to look up <...> file "
           "names")
       .label("path")
-      .handler([&](std::string s) { searchPath.push_back(s); });
+      .handler([&](const std::string& s) { searchPath.push_back(s); });
 }
 
 Bindings* MixEvalArgs::getAutoArgs(EvalState& state) {
diff --git a/third_party/nix/src/libexpr/eval.cc b/third_party/nix/src/libexpr/eval.cc
index 4be301167be9..4053dffe5185 100644
--- a/third_party/nix/src/libexpr/eval.cc
+++ b/third_party/nix/src/libexpr/eval.cc
@@ -298,7 +298,7 @@ static Strings parseNixPath(const string& s) {
   return res;
 }
 
-EvalState::EvalState(const Strings& _searchPath, ref<Store> store)
+EvalState::EvalState(const Strings& _searchPath, const ref<Store>& store)
     : sWith(symbols.create("<with>")),
       sOutPath(symbols.create("outPath")),
       sDrvPath(symbols.create("drvPath")),
diff --git a/third_party/nix/src/libexpr/eval.hh b/third_party/nix/src/libexpr/eval.hh
index 48c67b62295d..48400d5f08e2 100644
--- a/third_party/nix/src/libexpr/eval.hh
+++ b/third_party/nix/src/libexpr/eval.hh
@@ -105,7 +105,7 @@ class EvalState {
   std::unordered_map<Path, Path> resolvedPaths;
 
  public:
-  EvalState(const Strings& _searchPath, ref<Store> store);
+  EvalState(const Strings& _searchPath, const ref<Store>& store);
   ~EvalState();
 
   void addToSearchPath(const string& s);
diff --git a/third_party/nix/src/libexpr/get-drvs.cc b/third_party/nix/src/libexpr/get-drvs.cc
index c4afc0fb45eb..39870abcbdfa 100644
--- a/third_party/nix/src/libexpr/get-drvs.cc
+++ b/third_party/nix/src/libexpr/get-drvs.cc
@@ -15,7 +15,7 @@ namespace nix {
 DrvInfo::DrvInfo(EvalState& state, string attrPath, Bindings* attrs)
     : state(&state), attrs(attrs), attrPath(std::move(attrPath)) {}
 
-DrvInfo::DrvInfo(EvalState& state, ref<Store> store,
+DrvInfo::DrvInfo(EvalState& state, const ref<Store>& store,
                  const std::string& drvPathWithOutputs)
     : state(&state), attrPath("") {
   auto spec = parseDrvPathWithOutputs(drvPathWithOutputs);
diff --git a/third_party/nix/src/libexpr/get-drvs.hh b/third_party/nix/src/libexpr/get-drvs.hh
index ef6ecd253e6a..f0de0f67b8da 100644
--- a/third_party/nix/src/libexpr/get-drvs.hh
+++ b/third_party/nix/src/libexpr/get-drvs.hh
@@ -34,7 +34,7 @@ struct DrvInfo {
 
   DrvInfo(EvalState& state) : state(&state){};
   DrvInfo(EvalState& state, string attrPath, Bindings* attrs);
-  DrvInfo(EvalState& state, ref<Store> store,
+  DrvInfo(EvalState& state, const ref<Store>& store,
           const std::string& drvPathWithOutputs);
 
   string queryName() const;
diff --git a/third_party/nix/src/libexpr/primops.cc b/third_party/nix/src/libexpr/primops.cc
index 7b73bec03525..307459396eae 100644
--- a/third_party/nix/src/libexpr/primops.cc
+++ b/third_party/nix/src/libexpr/primops.cc
@@ -34,7 +34,7 @@ namespace nix {
    name>. */
 std::pair<string, string> decodeContext(const string& s) {
   if (s.at(0) == '!') {
-    size_t index = s.find("!", 1);
+    size_t index = s.find('!', 1);
     return std::pair<string, string>(string(s, index + 1),
                                      string(s, 1, index - 1));
   }
@@ -2172,7 +2172,7 @@ static void prim_splitVersion(EvalState& state, const Pos& pos, Value** args,
   unsigned int n = 0;
   for (auto& component : components) {
     auto listElem = v.listElems()[n++] = state.allocValue();
-    mkString(*listElem, std::move(component));
+    mkString(*listElem, component);
   }
 }
 
@@ -2246,7 +2246,8 @@ static void prim_fetchTarball(EvalState& state, const Pos& pos, Value** args,
 
 RegisterPrimOp::PrimOps* RegisterPrimOp::primOps;
 
-RegisterPrimOp::RegisterPrimOp(std::string name, size_t arity, PrimOpFun fun) {
+RegisterPrimOp::RegisterPrimOp(const std::string& name, size_t arity,
+                               PrimOpFun fun) {
   if (primOps == nullptr) {
     primOps = new PrimOps;
   }
diff --git a/third_party/nix/src/libexpr/primops.hh b/third_party/nix/src/libexpr/primops.hh
index 8e674509c7c4..6abd0508a09b 100644
--- a/third_party/nix/src/libexpr/primops.hh
+++ b/third_party/nix/src/libexpr/primops.hh
@@ -11,7 +11,7 @@ struct RegisterPrimOp {
   /* You can register a constant by passing an arity of 0. fun
      will get called during EvalState initialization, so there
      may be primops not yet added and builtins is not yet sorted. */
-  RegisterPrimOp(std::string name, size_t arity, PrimOpFun fun);
+  RegisterPrimOp(const std::string& name, size_t arity, PrimOpFun fun);
 };
 
 /* These primops are disabled without enableNativeCode, but plugins