refactor(3p/nix): Apply clang-tidy's performance-* fixes r/789

This applies the performance fixes listed here:

https://clang.llvm.org/extra/clang-tidy/checks/list.html

1 files changed, 4 insertions, 3 deletions

diff --git a/third_party/nix/src/libexpr/primops.cc b/third_party/nix/src/libexpr/primops.cc
index 7b73bec035..307459396e 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;
   }