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

This applies the modernization fixes listed here:

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

The 'modernize-use-trailing-return-type' fix was excluded due to my
personal preference (more specifically, I think the 'auto' keyword is
misleading in that position).

third_party/nix/src/libexpr/attr-path.cc

@@ -15,7 +15,7 @@ static Strings parseAttrPath(const string& s) {
       cur.clear();
     } else if (*i == '"') {
       ++i;
-      while (1) {
+      while (true) {
         if (i == s.end()) {
           throw Error(format("missing closing quote in selection path '%1%'") %
                       s);

third_party/nix/src/libexpr/eval.cc

@@ -328,7 +328,7 @@ EvalState::EvalState(const Strings& _searchPath, ref<Store> store)
       repair(NoRepair),
       store(store),
       baseEnv(allocEnv(128)),
-      staticBaseEnv(false, 0) {
+      staticBaseEnv(false, nullptr) {
   countCalls = getEnv("NIX_COUNT_CALLS", "0") != "0";
 
   assert(gcInitialised);
@@ -378,7 +378,7 @@ EvalState::EvalState(const Strings& _searchPath, ref<Store> store)
   createBaseEnv();
 }
 
-EvalState::~EvalState() {}
+EvalState::~EvalState() = default;
 
 Path EvalState::checkSourcePath(const Path& path_) {
   if (!allowedPaths) {
@@ -575,7 +575,7 @@ Value& mkString(Value& v, const string& s, const PathSet& context) {
     for (auto& i : context) {
       v.string.context[n++] = dupString(i.c_str());
     }
-    v.string.context[n] = 0;
+    v.string.context[n] = nullptr;
   }
   return v;
 }
@@ -591,10 +591,10 @@ inline Value* EvalState::lookupVar(Env* env, const ExprVar& var, bool noEval) {
     return env->values[var.displ];
   }
 
-  while (1) {
+  while (true) {
     if (env->type == Env::HasWithExpr) {
       if (noEval) {
-        return 0;
+        return nullptr;
       }
       Value* v = allocValue();
       evalAttrs(*env->up, (Expr*)env->values[0], *v);
@@ -656,7 +656,8 @@ void EvalState::mkList(Value& v, size_t size) {
   } else {
     v.type = tListN;
     v.bigList.size = size;
-    v.bigList.elems = size ? (Value**)allocBytes(size * sizeof(Value*)) : 0;
+    v.bigList.elems =
+        size ? (Value**)allocBytes(size * sizeof(Value*)) : nullptr;
   }
   nrListElems += size;
 }
@@ -822,7 +823,7 @@ void ExprAttrs::eval(EvalState& state, Env& env, Value& v) {
     env2.up = &env;
     dynamicEnv = &env2;
 
-    AttrDefs::iterator overrides = attrs.find(state.sOverrides);
+    auto overrides = attrs.find(state.sOverrides);
     bool hasOverrides = overrides != attrs.end();
 
     /* The recursive attributes are evaluated in the new
@@ -858,7 +859,7 @@ void ExprAttrs::eval(EvalState& state, Env& env, Value& v) {
         newBnds->push_back(i);
       }
       for (auto& i : *vOverrides->attrs) {
-        AttrDefs::iterator j = attrs.find(i.name);
+        auto j = attrs.find(i.name);
         if (j != attrs.end()) {
           (*newBnds)[j->second.displ] = i;
           env2.values[j->second.displ] = i.value;
@@ -955,7 +956,7 @@ unsigned long nrLookups = 0;
 
 void ExprSelect::eval(EvalState& state, Env& env, Value& v) {
   Value vTmp;
-  Pos* pos2 = 0;
+  Pos* pos2 = nullptr;
   Value* vAttrs = &vTmp;
 
   e->eval(state, env, vTmp);
@@ -985,7 +986,7 @@ void ExprSelect::eval(EvalState& state, Env& env, Value& v) {
       }
     }
 
-    state.forceValue(*vAttrs, (pos2 != NULL ? *pos2 : this->pos));
+    state.forceValue(*vAttrs, (pos2 != nullptr ? *pos2 : this->pos));
 
   } catch (Error& e) {
     if (pos2 && pos2->file != state.sDerivationNix) {
@@ -1334,7 +1335,7 @@ void EvalState::concatLists(Value& v, size_t nrLists, Value** lists,
                             const Pos& pos) {
   nrListConcats++;
 
-  Value* nonEmpty = 0;
+  Value* nonEmpty = nullptr;
   size_t len = 0;
   for (size_t n = 0; n < nrLists; ++n) {
     forceList(*lists[n], pos);
@@ -1796,7 +1797,7 @@ void EvalState::printStats() {
 
 #if HAVE_BOEHMGC
   GC_word heapSize, totalBytes;
-  GC_get_heap_usage_safe(&heapSize, 0, 0, 0, &totalBytes);
+  GC_get_heap_usage_safe(&heapSize, nullptr, nullptr, nullptr, &totalBytes);
 #endif
   if (showStats) {
     auto outPath = getEnv("NIX_SHOW_STATS_PATH", "-");

third_party/nix/src/libexpr/get-drvs.cc

@@ -2,6 +2,7 @@
 
 #include <cstring>
 #include <regex>
+#include <utility>
 
 #include <glog/logging.h>
 
@@ -11,12 +12,12 @@
 
 namespace nix {
 
-DrvInfo::DrvInfo(EvalState& state, const string& attrPath, Bindings* attrs)
-    : state(&state), attrs(attrs), attrPath(attrPath) {}
+DrvInfo::DrvInfo(EvalState& state, string attrPath, Bindings* attrs)
+    : state(&state), attrs(attrs), attrPath(std::move(attrPath)) {}
 
 DrvInfo::DrvInfo(EvalState& state, ref<Store> store,
                  const std::string& drvPathWithOutputs)
-    : state(&state), attrs(nullptr), attrPath("") {
+    : state(&state), attrPath("") {
   auto spec = parseDrvPathWithOutputs(drvPathWithOutputs);
 
   drvPath = spec.first;
@@ -158,11 +159,11 @@ Bindings* DrvInfo::getMeta() {
     return meta;
   }
   if (!attrs) {
-    return 0;
+    return nullptr;
   }
   Bindings::iterator a = attrs->find(state->sMeta);
   if (a == attrs->end()) {
-    return 0;
+    return nullptr;
   }
   state->forceAttrs(*a->value, *a->pos);
   meta = a->value->attrs;
@@ -208,11 +209,11 @@ bool DrvInfo::checkMeta(Value& v) {
 
 Value* DrvInfo::queryMeta(const string& name) {
   if (!getMeta()) {
-    return 0;
+    return nullptr;
   }
   Bindings::iterator a = meta->find(state->symbols.create(name));
   if (a == meta->end() || !checkMeta(*a->value)) {
-    return 0;
+    return nullptr;
   }
   return a->value;
 }
@@ -303,7 +304,7 @@ void DrvInfo::setMeta(const string& name, Value* v) {
 }
 
 /* Cache for already considered attrsets. */
-typedef set<Bindings*> Done;
+using Done = set<Bindings*>;
 
 /* Evaluate value `v'.  If it evaluates to a set of type `derivation',
    then put information about it in `drvs' (unless it's already in `done').

third_party/nix/src/libexpr/get-drvs.hh

@@ -33,7 +33,7 @@ struct DrvInfo {
   string attrPath; /* path towards the derivation */
 
   DrvInfo(EvalState& state) : state(&state){};
-  DrvInfo(EvalState& state, const string& attrPath, Bindings* attrs);
+  DrvInfo(EvalState& state, string attrPath, Bindings* attrs);
   DrvInfo(EvalState& state, ref<Store> store,
           const std::string& drvPathWithOutputs);
 

third_party/nix/src/libexpr/json-to-value.cc

@@ -66,7 +66,7 @@ static void parseJSON(EvalState& state, const char*& s, Value& v) {
     ValueVector values;
     values.reserve(128);
     skipWhitespace(s);
-    while (1) {
+    while (true) {
       if (values.empty() && *s == ']') {
         break;
       }
@@ -92,7 +92,7 @@ static void parseJSON(EvalState& state, const char*& s, Value& v) {
   else if (*s == '{') {
     s++;
     ValueMap attrs;
-    while (1) {
+    while (true) {
       skipWhitespace(s);
       if (attrs.empty() && *s == '}') {
         break;

third_party/nix/src/libexpr/names.cc

@@ -1,5 +1,7 @@
 #include "names.hh"
 
+#include <memory>
+
 #include "util.hh"
 
 namespace nix {
@@ -26,8 +28,7 @@ DrvName::DrvName(const string& s) : hits(0) {
 bool DrvName::matches(DrvName& n) {
   if (name != "*") {
     if (!regex) {
-      regex = std::unique_ptr<std::regex>(
-          new std::regex(name, std::regex::extended));
+      regex = std::make_unique<std::regex>(name, std::regex::extended);
     }
     if (!std::regex_match(n.name, *regex)) {
       return false;

third_party/nix/src/libexpr/nixexpr.cc

@@ -239,7 +239,7 @@ void ExprVar::bindVars(const StaticEnv& env) {
         withLevel = level;
       }
     } else {
-      StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
+      auto i = curEnv->vars.find(name);
       if (i != curEnv->vars.end()) {
         fromWith = false;
         this->level = level;

third_party/nix/src/libexpr/primops.cc

@@ -62,7 +62,7 @@ void EvalState::realiseContext(const PathSet& context) {
          paths. */
       if (allowedPaths) {
         auto drv = store->derivationFromPath(decoded.first);
-        DerivationOutputs::iterator i = drv.outputs.find(decoded.second);
+        auto i = drv.outputs.find(decoded.second);
         if (i == drv.outputs.end()) {
           throw Error("derivation '%s' does not have an output named '%s'",
                       decoded.first, decoded.second);
@@ -160,7 +160,7 @@ static void prim_scopedImport(EvalState& state, const Pos& pos, Value** args,
 
 /* Want reasonable symbol names, so extern C */
 /* !!! Should we pass the Pos or the file name too? */
-extern "C" typedef void (*ValueInitializer)(EvalState& state, Value& v);
+extern "C" using ValueInitializer = void(*)(EvalState&, Value&);
 
 /* Load a ValueInitializer from a DSO and return whatever it initializes */
 void prim_importNative(EvalState& state, const Pos& pos, Value** args,
@@ -186,7 +186,7 @@ void prim_importNative(EvalState& state, const Pos& pos, Value** args,
   }
 
   dlerror();
-  ValueInitializer func = (ValueInitializer)dlsym(handle, sym.c_str());
+  auto func = (ValueInitializer)dlsym(handle, sym.c_str());
   if (!func) {
     char* message = dlerror();
     if (message) {
@@ -2090,7 +2090,7 @@ static void prim_replaceStrings(EvalState& state, const Pos& pos, Value** args,
   for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
     PathSet ctx;
     auto s = state.forceString(*args[1]->listElems()[n], ctx, pos);
-    to.push_back(std::make_pair(std::move(s), std::move(ctx)));
+    to.emplace_back(std::move(s), std::move(ctx));
   }
 
   PathSet context;
@@ -2253,7 +2253,7 @@ RegisterPrimOp::RegisterPrimOp(std::string name, size_t arity, PrimOpFun fun) {
 }
 
 void EvalState::createBaseEnv() {
-  baseEnv.up = 0;
+  baseEnv.up = nullptr;
 
   /* Add global constants such as `true' to the base environment. */
   Value v;
@@ -2281,7 +2281,7 @@ void EvalState::createBaseEnv() {
   };
 
   if (!evalSettings.pureEval) {
-    mkInt(v, time(0));
+    mkInt(v, time(nullptr));
     addConstant("__currentTime", v);
   }