style(3p/nix): Remove 'using std::*' from types.hh r/840

It is considered bad form to use things from includes in headers, as
these directives propagate to everywhere else and can make it
confusing.

types.hh (which is includes almost literally everywhere) had some of
these directives, which this commit removes.

14 files changed, 183 insertions, 180 deletions

diff --git a/third_party/nix/src/libutil/archive.cc b/third_party/nix/src/libutil/archive.cc
index 32bad07f22da..f78727c5fb46 100644
--- a/third_party/nix/src/libutil/archive.cc
+++ b/third_party/nix/src/libutil/archive.cc
@@ -38,7 +38,7 @@ static GlobalConfig::Register r1(&archiveSettings);
 
 const std::string narVersionMagic1 = "nix-archive-1";
 
-static string caseHackSuffix = "~nix~case~hack~";
+static std::string caseHackSuffix = "~nix~case~hack~";
 
 PathFilter defaultPathFilter = [](const Path& /*unused*/) { return true; };
 
@@ -89,12 +89,12 @@ static void dump(const Path& path, Sink& sink, PathFilter& filter) {
 
     /* If we're on a case-insensitive system like macOS, undo
        the case hack applied by restorePath(). */
-    std::map<string, string> unhacked;
+    std::map<std::string, std::string> unhacked;
     for (auto& i : readDirectory(path)) {
       if (archiveSettings.useCaseHack) {
-        string name(i.name);
+        std::string name(i.name);
         size_t pos = i.name.find(caseHackSuffix);
-        if (pos != string::npos) {
+        if (pos != std::string::npos) {
           DLOG(INFO) << "removing case hack suffix from " << path << "/"
                      << i.name;
 
@@ -145,7 +145,7 @@ void dumpString(const std::string& s, Sink& sink) {
        << "contents" << s << ")";
 }
 
-static SerialisationError badArchive(const string& s) {
+static SerialisationError badArchive(const std::string& s) {
   return SerialisationError("bad archive: " + s);
 }
 
@@ -182,13 +182,13 @@ static void parseContents(ParseSink& sink, Source& source, const Path& path) {
 }
 
 struct CaseInsensitiveCompare {
-  bool operator()(const string& a, const string& b) const {
+  bool operator()(const std::string& a, const std::string& b) const {
     return strcasecmp(a.c_str(), b.c_str()) < 0;
   }
 };
 
 static void parse(ParseSink& sink, Source& source, const Path& path) {
-  string s;
+  std::string s;
 
   s = readString(source);
   if (s != "(") {
@@ -212,7 +212,7 @@ static void parse(ParseSink& sink, Source& source, const Path& path) {
       if (type != tpUnknown) {
         throw badArchive("multiple type fields");
       }
-      string t = readString(source);
+      std::string t = readString(source);
 
       if (t == "regular") {
         type = tpRegular;
@@ -247,8 +247,8 @@ static void parse(ParseSink& sink, Source& source, const Path& path) {
     }
 
     else if (s == "entry" && type == tpDirectory) {
-      string name;
-      string prevName;
+      std::string name;
+      std::string prevName;
 
       s = readString(source);
       if (s != "(") {
@@ -266,8 +266,8 @@ static void parse(ParseSink& sink, Source& source, const Path& path) {
         if (s == "name") {
           name = readString(source);
           if (name.empty() || name == "." || name == ".." ||
-              name.find('/') != string::npos ||
-              name.find((char)0) != string::npos) {
+              name.find('/') != std::string::npos ||
+              name.find((char)0) != std::string::npos) {
             throw Error(format("NAR contains invalid file name '%1%'") % name);
           }
           if (name <= prevName) {
@@ -297,7 +297,7 @@ static void parse(ParseSink& sink, Source& source, const Path& path) {
     }
 
     else if (s == "target" && type == tpSymlink) {
-      string target = readString(source);
+      std::string target = readString(source);
       sink.createSymlink(path, target);
     }
 
@@ -308,7 +308,7 @@ static void parse(ParseSink& sink, Source& source, const Path& path) {
 }
 
 void parseDump(ParseSink& sink, Source& source) {
-  string version;
+  std::string version;
   try {
     version = readString(source, narVersionMagic1.size());
   } catch (SerialisationError& e) {
@@ -369,7 +369,7 @@ struct RestoreSink : ParseSink {
     writeFull(fd.get(), data, len);
   }
 
-  void createSymlink(const Path& path, const string& target) override {
+  void createSymlink(const Path& path, const std::string& target) override {
     Path p = dstPath + path;
     nix::createSymlink(target, p);
   }
diff --git a/third_party/nix/src/libutil/archive.hh b/third_party/nix/src/libutil/archive.hh
index 9a656edae4a3..0afa8893efdd 100644
--- a/third_party/nix/src/libutil/archive.hh
+++ b/third_party/nix/src/libutil/archive.hh
@@ -56,7 +56,7 @@ struct ParseSink {
   virtual void preallocateContents(unsigned long long size){};
   virtual void receiveContents(unsigned char* data, unsigned int len){};
 
-  virtual void createSymlink(const Path& path, const string& target){};
+  virtual void createSymlink(const Path& path, const std::string& target){};
 };
 
 struct TeeSink : ParseSink {
diff --git a/third_party/nix/src/libutil/args.cc b/third_party/nix/src/libutil/args.cc
index 48fa715fdf0f..4e7bcb3ae72b 100644
--- a/third_party/nix/src/libutil/args.cc
+++ b/third_party/nix/src/libutil/args.cc
@@ -27,14 +27,14 @@ void Args::parseCmdline(const Strings& _cmdline) {
        `-j3` -> `-j 3`). */
     if (!dashDash && arg.length() > 2 && arg[0] == '-' && arg[1] != '-' &&
         (isalpha(arg[1]) != 0)) {
-      *pos = (string) "-" + arg[1];
+      *pos = (std::string) "-" + arg[1];
       auto next = pos;
       ++next;
       for (unsigned int j = 2; j < arg.length(); j++) {
         if (isalpha(arg[j]) != 0) {
-          cmdline.insert(next, (string) "-" + arg[j]);
+          cmdline.insert(next, (std::string) "-" + arg[j]);
         } else {
-          cmdline.insert(next, string(arg, j));
+          cmdline.insert(next, std::string(arg, j));
           break;
         }
       }
@@ -59,7 +59,7 @@ void Args::parseCmdline(const Strings& _cmdline) {
   processArgs(pendingArgs, true);
 }
 
-void Args::printHelp(const string& programName, std::ostream& out) {
+void Args::printHelp(const std::string& programName, std::ostream& out) {
   std::cout << "Usage: " << programName << " <FLAGS>...";
   for (auto& exp : expectedArgs) {
     std::cout << renderLabels({exp.label});
@@ -121,15 +121,15 @@ bool Args::processFlag(Strings::iterator& pos, Strings::iterator end) {
     return true;
   };
 
-  if (string(*pos, 0, 2) == "--") {
-    auto i = longFlags.find(string(*pos, 2));
+  if (std::string(*pos, 0, 2) == "--") {
+    auto i = longFlags.find(std::string(*pos, 2));
     if (i == longFlags.end()) {
       return false;
     }
     return process("--" + i->first, *i->second);
   }
 
-  if (string(*pos, 0, 1) == "-" && pos->size() == 2) {
+  if (std::string(*pos, 0, 1) == "-" && pos->size() == 2) {
     auto c = (*pos)[1];
     auto i = shortFlags.find(c);
     if (i == shortFlags.end()) {
diff --git a/third_party/nix/src/libutil/args.hh b/third_party/nix/src/libutil/args.hh
index 20233d353424..20a6379fecba 100644
--- a/third_party/nix/src/libutil/args.hh
+++ b/third_party/nix/src/libutil/args.hh
@@ -18,7 +18,7 @@ class Args {
      wrong. */
   void parseCmdline(const Strings& cmdline);
 
-  virtual void printHelp(const string& programName, std::ostream& out);
+  virtual void printHelp(const std::string& programName, std::ostream& out);
 
   virtual std::string description() { return ""; }
 
@@ -187,7 +187,7 @@ class Args {
   }
 
   /* Expect a string argument. */
-  void expectArg(const std::string& label, string* dest,
+  void expectArg(const std::string& label, std::string* dest,
                  bool optional = false) {
     expectedArgs.push_back(
         ExpectedArg{label, 1, optional,
diff --git a/third_party/nix/src/libutil/config.cc b/third_party/nix/src/libutil/config.cc
index 828ee1811bdb..c7c952abf16f 100644
--- a/third_party/nix/src/libutil/config.cc
+++ b/third_party/nix/src/libutil/config.cc
@@ -82,23 +82,23 @@ void Config::getSettings(std::map<std::string, SettingInfo>& res,
 
 void AbstractConfig::applyConfigFile(const Path& path) {
   try {
-    string contents = readFile(path);
+    std::string contents = readFile(path);
 
     unsigned int pos = 0;
 
     while (pos < contents.size()) {
-      string line;
+      std::string line;
       while (pos < contents.size() && contents[pos] != '\n') {
         line += contents[pos++];
       }
       pos++;
 
-      string::size_type hash = line.find('#');
-      if (hash != string::npos) {
-        line = string(line, 0, hash);
+      std::string::size_type hash = line.find('#');
+      if (hash != std::string::npos) {
+        line = std::string(line, 0, hash);
       }
 
-      auto tokens = tokenizeString<vector<string> >(line);
+      auto tokens = tokenizeString<std::vector<std::string> >(line);
       if (tokens.empty()) {
         continue;
       }
@@ -136,7 +136,7 @@ void AbstractConfig::applyConfigFile(const Path& path) {
                          path);
       }
 
-      string name = tokens[0];
+      std::string name = tokens[0];
 
       auto i = tokens.begin();
       advance(i, 2);
diff --git a/third_party/nix/src/libutil/hash.cc b/third_party/nix/src/libutil/hash.cc
index 81d8628e972b..07a9730551da 100644
--- a/third_party/nix/src/libutil/hash.cc
+++ b/third_party/nix/src/libutil/hash.cc
@@ -63,26 +63,26 @@ bool Hash::operator<(const Hash& h) const {
   return false;
 }
 
-const string base16Chars = "0123456789abcdef";
+const std::string base16Chars = "0123456789abcdef";
 
-static string printHash16(const Hash& hash) {
+static std::string printHash16(const Hash& hash) {
   char buf[hash.hashSize * 2];
   for (unsigned int i = 0; i < hash.hashSize; i++) {
     buf[i * 2] = base16Chars[hash.hash[i] >> 4];
     buf[i * 2 + 1] = base16Chars[hash.hash[i] & 0x0f];
   }
-  return string(buf, hash.hashSize * 2);
+  return std::string(buf, hash.hashSize * 2);
 }
 
 // omitted: E O U T
-const string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
+const std::string base32Chars = "0123456789abcdfghijklmnpqrsvwxyz";
 
-static string printHash32(const Hash& hash) {
+static std::string printHash32(const Hash& hash) {
   assert(hash.hashSize);
   size_t len = hash.base32Len();
   assert(len);
 
-  string s;
+  std::string s;
   s.reserve(len);
 
   for (int n = (int)len - 1; n >= 0; n--) {
@@ -98,7 +98,7 @@ static string printHash32(const Hash& hash) {
   return s;
 }
 
-string printHash16or32(const Hash& hash) {
+std::string printHash16or32(const Hash& hash) {
   return hash.to_string(hash.type == htMD5 ? Base16 : Base32, false);
 }
 
@@ -128,17 +128,17 @@ Hash::Hash(const std::string& s, HashType type) : type(type) {
   bool isSRI = false;
 
   auto sep = s.find(':');
-  if (sep == string::npos) {
+  if (sep == std::string::npos) {
     sep = s.find('-');
-    if (sep != string::npos) {
+    if (sep != std::string::npos) {
       isSRI = true;
     } else if (type == htUnknown) {
       throw BadHash("hash '%s' does not include a type", s);
     }
   }
 
-  if (sep != string::npos) {
-    string hts = string(s, 0, sep);
+  if (sep != std::string::npos) {
+    std::string hts = std::string(s, 0, sep);
     this->type = parseHashType(hts);
     if (this->type == htUnknown) {
       throw BadHash("unknown hash type '%s'", hts);
@@ -259,7 +259,7 @@ static void finish(HashType ht, Ctx& ctx, unsigned char* hash) {
   }
 }
 
-Hash hashString(HashType ht, const string& s) {
+Hash hashString(HashType ht, const std::string& s) {
   Ctx ctx;
   Hash hash(ht);
   start(ht, ctx);
@@ -338,7 +338,7 @@ Hash compressHash(const Hash& hash, unsigned int newSize) {
   return h;
 }
 
-HashType parseHashType(const string& s) {
+HashType parseHashType(const std::string& s) {
   if (s == "md5") {
     return htMD5;
   }
@@ -353,7 +353,7 @@ HashType parseHashType(const string& s) {
   }
 }
 
-string printHashType(HashType ht) {
+std::string printHashType(HashType ht) {
   if (ht == htMD5) {
     return "md5";
   }
diff --git a/third_party/nix/src/libutil/hash.hh b/third_party/nix/src/libutil/hash.hh
index a9002023fa31..f9c63c155ead 100644
--- a/third_party/nix/src/libutil/hash.hh
+++ b/third_party/nix/src/libutil/hash.hh
@@ -14,7 +14,7 @@ const int sha1HashSize = 20;
 const int sha256HashSize = 32;
 const int sha512HashSize = 64;
 
-extern const string base32Chars;
+extern const std::string base32Chars;
 
 enum Base : int { Base64, Base32, Base16, SRI };
 
@@ -68,10 +68,10 @@ struct Hash {
 };
 
 /* Print a hash in base-16 if it's MD5, or base-32 otherwise. */
-string printHash16or32(const Hash& hash);
+std::string printHash16or32(const Hash& hash);
 
 /* Compute the hash of the given string. */
-Hash hashString(HashType ht, const string& s);
+Hash hashString(HashType ht, const std::string& s);
 
 /* Compute the hash of the given file. */
 Hash hashFile(HashType ht, const Path& path);
@@ -87,10 +87,10 @@ HashResult hashPath(HashType ht, const Path& path,
 Hash compressHash(const Hash& hash, unsigned int newSize);
 
 /* Parse a string representing a hash type. */
-HashType parseHashType(const string& s);
+HashType parseHashType(const std::string& s);
 
 /* And the reverse. */
-string printHashType(HashType ht);
+std::string printHashType(HashType ht);
 
 union Ctx;
 
diff --git a/third_party/nix/src/libutil/serialise.cc b/third_party/nix/src/libutil/serialise.cc
index 34af4e840ab6..52f0b5542601 100644
--- a/third_party/nix/src/libutil/serialise.cc
+++ b/third_party/nix/src/libutil/serialise.cc
@@ -223,7 +223,7 @@ void writeString(const unsigned char* buf, size_t len, Sink& sink) {
   writePadding(len, sink);
 }
 
-Sink& operator<<(Sink& sink, const string& s) {
+Sink& operator<<(Sink& sink, const std::string& s) {
   writeString((const unsigned char*)s.data(), s.size(), sink);
   return sink;
 }
@@ -269,7 +269,7 @@ size_t readString(unsigned char* buf, size_t max, Source& source) {
   return len;
 }
 
-string readString(Source& source, size_t max) {
+std::string readString(Source& source, size_t max) {
   auto len = readNum<size_t>(source);
   if (len > max) {
     throw SerialisationError("string is too long");
@@ -280,7 +280,7 @@ string readString(Source& source, size_t max) {
   return res;
 }
 
-Source& operator>>(Source& in, string& s) {
+Source& operator>>(Source& in, std::string& s) {
   s = readString(in);
   return in;
 }
diff --git a/third_party/nix/src/libutil/serialise.hh b/third_party/nix/src/libutil/serialise.hh
index a5992b50ec6e..dc877487ee7e 100644
--- a/third_party/nix/src/libutil/serialise.hh
+++ b/third_party/nix/src/libutil/serialise.hh
@@ -135,9 +135,9 @@ struct StringSink : Sink {
 
 /* A source that reads data from a string. */
 struct StringSource : Source {
-  const string& s;
+  const std::string& s;
   size_t pos;
-  StringSource(const string& _s) : s(_s), pos(0) {}
+  StringSource(const std::string& _s) : s(_s), pos(0) {}
   size_t read(unsigned char* data, size_t len) override;
 };
 
@@ -231,7 +231,7 @@ inline Sink& operator<<(Sink& sink, uint64_t n) {
   return sink;
 }
 
-Sink& operator<<(Sink& sink, const string& s);
+Sink& operator<<(Sink& sink, const std::string& s);
 Sink& operator<<(Sink& sink, const Strings& s);
 Sink& operator<<(Sink& sink, const StringSet& s);
 
@@ -265,12 +265,12 @@ inline uint64_t readLongLong(Source& source) {
 
 void readPadding(size_t len, Source& source);
 size_t readString(unsigned char* buf, size_t max, Source& source);
-string readString(Source& source,
-                  size_t max = std::numeric_limits<size_t>::max());
+std::string readString(Source& source,
+                       size_t max = std::numeric_limits<size_t>::max());
 template <class T>
 T readStrings(Source& source);
 
-Source& operator>>(Source& in, string& s);
+Source& operator>>(Source& in, std::string& s);
 
 template <typename T>
 Source& operator>>(Source& in, T& n) {
diff --git a/third_party/nix/src/libutil/types.hh b/third_party/nix/src/libutil/types.hh
index ac1b802ce0f1..ad44719afe3a 100644
--- a/third_party/nix/src/libutil/types.hh
+++ b/third_party/nix/src/libutil/types.hh
@@ -22,10 +22,6 @@ namespace nix {
 
 /* Inherit some names from other namespaces for convenience. */
 using boost::format;
-using std::list;
-using std::set;
-using std::string;
-using std::vector;
 
 /* A variadic template that does nothing. Useful to call a function
    for all variadic arguments but ignoring the result. */
@@ -35,8 +31,8 @@ struct nop {
 };
 
 struct FormatOrString {
-  string s;
-  FormatOrString(const string& s) : s(s){};
+  std::string s;
+  FormatOrString(const std::string& s) : s(s){};
   FormatOrString(const format& f) : s(f.str()){};
   FormatOrString(const char* s) : s(s){};
 };
@@ -64,8 +60,8 @@ inline std::string fmt(const std::string& fs, Args... args) {
    a subclass. Catch Error instead. */
 class BaseError : public std::exception {
  protected:
-  string prefix_;  // used for location traces etc.
-  string err;
+  std::string prefix_;  // used for location traces etc.
+  std::string err;
 
  public:
   unsigned int status = 1;  // exit status
@@ -84,8 +80,8 @@ class BaseError : public std::exception {
   const char* what() const noexcept { return err.c_str(); }
 #endif
 
-  const string& msg() const { return err; }
-  const string& prefix() const { return prefix_; }
+  const std::string& msg() const { return err; }
+  const std::string& prefix() const { return prefix_; }
   BaseError& addPrefix(const FormatOrString& fs);
 };
 
@@ -108,13 +104,13 @@ MakeError(Error, BaseError)
   std::string addErrno(const std::string& s);
 };
 
-typedef list<string> Strings;
-typedef set<string> StringSet;
+typedef std::list<std::string> Strings;
+typedef std::set<std::string> StringSet;
 typedef std::map<std::string, std::string> StringMap;
 
 /* Paths are just strings. */
-typedef string Path;
-typedef list<Path> Paths;
-typedef set<Path> PathSet;
+typedef std::string Path;
+typedef std::list<Path> Paths;
+typedef std::set<Path> PathSet;
 
 }  // namespace nix
diff --git a/third_party/nix/src/libutil/util.cc b/third_party/nix/src/libutil/util.cc
index 53d037cf5801..696a8ff2365e 100644
--- a/third_party/nix/src/libutil/util.cc
+++ b/third_party/nix/src/libutil/util.cc
@@ -42,9 +42,9 @@ std::string SysError::addErrno(const std::string& s) {
   return s + ": " + strerror(errNo);
 }
 
-string getEnv(const string& key, const string& def) {
+std::string getEnv(const std::string& key, const std::string& def) {
   char* value = getenv(key.c_str());
-  return value != nullptr ? string(value) : def;
+  return value != nullptr ? std::string(value) : def;
 }
 
 std::map<std::string, std::string> getEnv() {
@@ -101,15 +101,15 @@ return canonPath(path);
 Path canonPath(const Path& path, bool resolveSymlinks) {
   assert(!path.empty());
 
-  string s;
+  std::string s;
 
   if (path[0] != '/') {
     throw Error(format("not an absolute path: '%1%'") % path);
   }
 
-  string::const_iterator i = path.begin();
-  string::const_iterator end = path.end();
-  string temp;
+  std::string::const_iterator i = path.begin();
+  std::string::const_iterator end = path.end();
+  std::string temp;
 
   /* Count the number of times we follow a symlink and stop at some
      arbitrary (but high) limit to prevent infinite loops. */
@@ -153,7 +153,7 @@ Path canonPath(const Path& path, bool resolveSymlinks) {
           throw Error(format("infinite symlink recursion in path '%1%'") %
                       path);
         }
-        temp = absPath(readLink(s), dirOf(s)) + string(i, end);
+        temp = absPath(readLink(s), dirOf(s)) + std::string(i, end);
         i = temp.begin(); /* restart */
         end = temp.end();
         s = "";
@@ -166,13 +166,13 @@ Path canonPath(const Path& path, bool resolveSymlinks) {
 
 Path dirOf(const Path& path) {
   Path::size_type pos = path.rfind('/');
-  if (pos == string::npos) {
+  if (pos == std::string::npos) {
     return ".";
   }
   return pos == 0 ? "/" : Path(path, 0, pos);
 }
 
-string baseNameOf(const Path& path) {
+std::string baseNameOf(const Path& path) {
   if (path.empty()) {
     return "";
   }
@@ -183,17 +183,17 @@ string baseNameOf(const Path& path) {
   }
 
   Path::size_type pos = path.rfind('/', last);
-  if (pos == string::npos) {
+  if (pos == std::string::npos) {
     pos = 0;
   } else {
     pos += 1;
   }
 
-  return string(path, pos, last - pos + 1);
+  return std::string(path, pos, last - pos + 1);
 }
 
 bool isInDir(const Path& path, const Path& dir) {
-  return path[0] == '/' && string(path, 0, dir.size()) == dir &&
+  return path[0] == '/' && std::string(path, 0, dir.size()) == dir &&
          path.size() >= dir.size() + 2 && path[dir.size()] == '/';
 }
 
@@ -235,7 +235,7 @@ Path readLink(const Path& path) {
       throw SysError("reading symbolic link '%1%'", path);
 
     } else if (rlSize < bufSize) {
-      return string(buf.data(), rlSize);
+      return std::string(buf.data(), rlSize);
     }
   }
 }
@@ -252,7 +252,7 @@ DirEntries readDirectory(DIR* dir, const Path& path) {
   struct dirent* dirent;
   while (errno = 0, dirent = readdir(dir)) { /* sic */
     checkInterrupt();
-    string name = dirent->d_name;
+    std::string name = dirent->d_name;
     if (name == "." || name == "..") {
       continue;
     }
@@ -294,7 +294,7 @@ unsigned char getFileType(const Path& path) {
   return DT_UNKNOWN;
 }
 
-string readFile(int fd) {
+std::string readFile(int fd) {
   struct stat st;
   if (fstat(fd, &st) == -1) {
     throw SysError("statting file");
@@ -303,10 +303,10 @@ string readFile(int fd) {
   std::vector<unsigned char> buf(st.st_size);
   readFull(fd, buf.data(), st.st_size);
 
-  return string((char*)buf.data(), st.st_size);
+  return std::string((char*)buf.data(), st.st_size);
 }
 
-string readFile(const Path& path, bool drain) {
+std::string readFile(const Path& path, bool drain) {
   AutoCloseFD fd = open(path.c_str(), O_RDONLY | O_CLOEXEC);
   if (!fd) {
     throw SysError(format("opening file '%1%'") % path);
@@ -322,7 +322,7 @@ void readFile(const Path& path, Sink& sink) {
   drainFD(fd.get(), sink);
 }
 
-void writeFile(const Path& path, const string& s, mode_t mode) {
+void writeFile(const Path& path, const std::string& s, mode_t mode) {
   AutoCloseFD fd =
       open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
   if (!fd) {
@@ -350,8 +350,8 @@ void writeFile(const Path& path, Source& source, mode_t mode) {
   }
 }
 
-string readLine(int fd) {
-  string s;
+std::string readLine(int fd) {
+  std::string s;
   while (true) {
     checkInterrupt();
     char ch;
@@ -372,7 +372,7 @@ string readLine(int fd) {
   }
 }
 
-void writeLine(int fd, string s) {
+void writeLine(int fd, std::string s) {
   s += '\n';
   writeFull(fd, s);
 }
@@ -381,7 +381,7 @@ static void _deletePath(int parentfd, const Path& path,
                         unsigned long long& bytesFreed) {
   checkInterrupt();
 
-  string name(baseNameOf(path));
+  std::string name(baseNameOf(path));
 
   struct stat st;
   if (fstatat(parentfd, name.c_str(), &st, AT_SYMLINK_NOFOLLOW) == -1) {
@@ -539,8 +539,8 @@ Path getConfigDir() {
 
 std::vector<Path> getConfigDirs() {
   Path configHome = getConfigDir();
-  string configDirs = getEnv("XDG_CONFIG_DIRS");
-  auto result = tokenizeString<std::vector<string>>(configDirs, ":");
+  std::string configDirs = getEnv("XDG_CONFIG_DIRS");
+  auto result = tokenizeString<std::vector<std::string>>(configDirs, ":");
   result.insert(result.begin(), configHome);
   return result;
 }
@@ -643,11 +643,11 @@ void writeFull(int fd, const unsigned char* buf, size_t count,
   }
 }
 
-void writeFull(int fd, const string& s, bool allowInterrupts) {
+void writeFull(int fd, const std::string& s, bool allowInterrupts) {
   writeFull(fd, (const unsigned char*)s.data(), s.size(), allowInterrupts);
 }
 
-string drainFD(int fd, bool block) {
+std::string drainFD(int fd, bool block) {
   StringSink sink;
   drainFD(fd, sink, block);
   return std::move(*sink.s);
@@ -694,7 +694,7 @@ void drainFD(int fd, Sink& sink, bool block) {
 
 AutoDelete::AutoDelete() : del{false} {}
 
-AutoDelete::AutoDelete(string p, bool recursive) : path(std::move(p)) {
+AutoDelete::AutoDelete(std::string p, bool recursive) : path(std::move(p)) {
   del = true;
   this->recursive = recursive;
 }
@@ -812,7 +812,7 @@ int Pid::kill() {
      process group, send the signal to every process in the child
      process group (which hopefully includes *all* its children). */
   if (::kill(separatePG ? -pid : pid, killSignal) != 0) {
-      LOG(ERROR) << SysError("killing process %d", pid).msg();
+    LOG(ERROR) << SysError("killing process %d", pid).msg();
   }
 
   return wait();
@@ -950,8 +950,9 @@ std::vector<char*> stringsToCharPtrs(const Strings& ss) {
   return res;
 }
 
-string runProgram(const Path& program, bool searchPath, const Strings& args,
-                  const std::optional<std::string>& input) {
+std::string runProgram(const Path& program, bool searchPath,
+                       const Strings& args,
+                       const std::optional<std::string>& input) {
   RunOptions opts(program, args);
   opts.searchPath = searchPath;
   opts.input = input;
@@ -1114,7 +1115,7 @@ void runProgram2(const RunOptions& options) {
   }
 }
 
-void closeMostFDs(const set<int>& exceptions) {
+void closeMostFDs(const std::set<int>& exceptions) {
 #if __linux__
   try {
     for (auto& s : readDirectory("/proc/self/fd")) {
@@ -1168,28 +1169,30 @@ void _interrupted() {
 //////////////////////////////////////////////////////////////////////
 
 template <class C>
-C tokenizeString(const string& s, const string& separators) {
+C tokenizeString(const std::string& s, const std::string& separators) {
   C result;
-  string::size_type pos = s.find_first_not_of(separators, 0);
-  while (pos != string::npos) {
-    string::size_type end = s.find_first_of(separators, pos + 1);
-    if (end == string::npos) {
+  std::string::size_type pos = s.find_first_not_of(separators, 0);
+  while (pos != std::string::npos) {
+    std::string::size_type end = s.find_first_of(separators, pos + 1);
+    if (end == std::string::npos) {
       end = s.size();
     }
-    string token(s, pos, end - pos);
+    std::string token(s, pos, end - pos);
     result.insert(result.end(), token);
     pos = s.find_first_not_of(separators, end);
   }
   return result;
 }
 
-template Strings tokenizeString(const string& s, const string& separators);
-template StringSet tokenizeString(const string& s, const string& separators);
-template vector<string> tokenizeString(const string& s,
-                                       const string& separators);
+template Strings tokenizeString(const std::string& s,
+                                const std::string& separators);
+template StringSet tokenizeString(const std::string& s,
+                                  const std::string& separators);
+template std::vector<std::string> tokenizeString(const std::string& s,
+                                                 const std::string& separators);
 
-string concatStringsSep(const string& sep, const Strings& ss) {
-  string s;
+std::string concatStringsSep(const std::string& sep, const Strings& ss) {
+  std::string s;
   for (auto& i : ss) {
     if (!s.empty()) {
       s += sep;
@@ -1199,8 +1202,8 @@ string concatStringsSep(const string& sep, const Strings& ss) {
   return s;
 }
 
-string concatStringsSep(const string& sep, const StringSet& ss) {
-  string s;
+std::string concatStringsSep(const std::string& sep, const StringSet& ss) {
+  std::string s;
   for (auto& i : ss) {
     if (!s.empty()) {
       s += sep;
@@ -1210,21 +1213,21 @@ string concatStringsSep(const string& sep, const StringSet& ss) {
   return s;
 }
 
-string trim(const string& s, const string& whitespace) {
+std::string trim(const std::string& s, const std::string& whitespace) {
   auto i = s.find_first_not_of(whitespace);
-  if (i == string::npos) {
+  if (i == std::string::npos) {
     return "";
   }
   auto j = s.find_last_not_of(whitespace);
-  return string(s, i, j == string::npos ? j : j - i + 1);
+  return std::string(s, i, j == std::string::npos ? j : j - i + 1);
 }
 
-string replaceStrings(const std::string& s, const std::string& from,
-                      const std::string& to) {
+std::string replaceStrings(const std::string& s, const std::string& from,
+                           const std::string& to) {
   if (from.empty()) {
     return s;
   }
-  string res = s;
+  std::string res = s;
   size_t pos = 0;
   while ((pos = res.find(from, pos)) != std::string::npos) {
     res.replace(pos, from.size(), to);
@@ -1233,7 +1236,7 @@ string replaceStrings(const std::string& s, const std::string& from,
   return res;
 }
 
-string statusToString(int status) {
+std::string statusToString(int status) {
   if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
     if (WIFEXITED(status)) {
       return (format("failed with exit code %1%") % WEXITSTATUS(status)).str();
@@ -1259,13 +1262,13 @@ bool statusOk(int status) {
   return WIFEXITED(status) && WEXITSTATUS(status) == 0;
 }
 
-bool hasPrefix(const string& s, const string& prefix) {
+bool hasPrefix(const std::string& s, const std::string& prefix) {
   return s.compare(0, prefix.size(), prefix) == 0;
 }
 
-bool hasSuffix(const string& s, const string& suffix) {
+bool hasSuffix(const std::string& s, const std::string& suffix) {
   return s.size() >= suffix.size() &&
-         string(s, s.size() - suffix.size()) == suffix;
+         std::string(s, s.size() - suffix.size()) == suffix;
 }
 
 std::string toLower(const std::string& s) {
@@ -1361,8 +1364,8 @@ std::string filterANSIEscapes(const std::string& s, bool filterAll,
 static char base64Chars[] =
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
-string base64Encode(const string& s) {
-  string res;
+std::string base64Encode(const std::string& s) {
+  std::string res;
   int data = 0;
   int nbits = 0;
 
@@ -1385,7 +1388,7 @@ string base64Encode(const string& s) {
   return res;
 }
 
-string base64Decode(const string& s) {
+std::string base64Decode(const std::string& s) {
   bool init = false;
   char decode[256];
   if (!init) {
@@ -1397,7 +1400,7 @@ string base64Decode(const string& s) {
     init = true;
   }
 
-  string res;
+  std::string res;
   unsigned int d = 0;
   unsigned int bits = 0;
 
diff --git a/third_party/nix/src/libutil/util.hh b/third_party/nix/src/libutil/util.hh
index 3c8d4bd70c06..7d10df50bf5b 100644
--- a/third_party/nix/src/libutil/util.hh
+++ b/third_party/nix/src/libutil/util.hh
@@ -32,7 +32,7 @@ struct Source;
 extern const std::string nativeSystem;
 
 /* Return an environment variable. */
-string getEnv(const string& key, const string& def = "");
+std::string getEnv(const std::string& key, const std::string& def = "");
 
 /* Get the entire environment. */
 std::map<std::string, std::string> getEnv();
@@ -59,7 +59,7 @@ Path dirOf(const Path& path);
 
 /* Return the base name of the given canonical path, i.e., everything
    following the final `/'. */
-string baseNameOf(const Path& path);
+std::string baseNameOf(const Path& path);
 
 /* Check whether 'path' is a descendant of 'dir'. */
 bool isInDir(const Path& path, const Path& dir);
@@ -82,34 +82,34 @@ bool isLink(const Path& path);
 /* Read the contents of a directory.  The entries `.' and `..' are
    removed. */
 struct DirEntry {
-  string name;
+  std::string name;
   ino_t ino;
   unsigned char type;  // one of DT_*
-  DirEntry(const string& name, ino_t ino, unsigned char type)
+  DirEntry(const std::string& name, ino_t ino, unsigned char type)
       : name(name), ino(ino), type(type) {}
 };
 
-typedef vector<DirEntry> DirEntries;
+typedef std::vector<DirEntry> DirEntries;
 
 DirEntries readDirectory(const Path& path);
 
 unsigned char getFileType(const Path& path);
 
 /* Read the contents of a file into a string. */
-string readFile(int fd);
-string readFile(const Path& path, bool drain = false);
+std::string readFile(int fd);
+std::string readFile(const Path& path, bool drain = false);
 void readFile(const Path& path, Sink& sink);
 
 /* Write a string to a file. */
-void writeFile(const Path& path, const string& s, mode_t mode = 0666);
+void writeFile(const Path& path, const std::string& s, mode_t mode = 0666);
 
 void writeFile(const Path& path, Source& source, mode_t mode = 0666);
 
 /* Read a line from a file descriptor. */
-string readLine(int fd);
+std::string readLine(int fd);
 
 /* Write a line to a file descriptor. */
-void writeLine(int fd, string s);
+void writeLine(int fd, std::string s);
 
 /* Delete a path; i.e., in the case of a directory, it is deleted
    recursively. It's not an error if the path does not exist. The
@@ -155,12 +155,12 @@ void replaceSymlink(const Path& target, const Path& link);
 void readFull(int fd, unsigned char* buf, size_t count);
 void writeFull(int fd, const unsigned char* buf, size_t count,
                bool allowInterrupts = true);
-void writeFull(int fd, const string& s, bool allowInterrupts = true);
+void writeFull(int fd, const std::string& s, bool allowInterrupts = true);
 
-MakeError(EndOfFile, Error)
+MakeError(EndOfFile, Error);
 
-    /* Read a file descriptor until EOF occurs. */
-    string drainFD(int fd, bool block = true);
+/* Read a file descriptor until EOF occurs. */
+std::string drainFD(int fd, bool block = true);
 
 void drainFD(int fd, Sink& sink, bool block = true);
 
@@ -235,7 +235,7 @@ void killUser(uid_t uid);
 /* Fork a process that runs the given function, and return the child
    pid to the caller. */
 struct ProcessOptions {
-  string errorPrefix = "error: ";
+  std::string errorPrefix = "error: ";
   bool dieWithParent = true;
   bool runExitHandlers = false;
   bool allowVfork = true;
@@ -246,9 +246,9 @@ pid_t startProcess(std::function<void()> fun,
 
 /* Run a program and return its stdout in a string (i.e., like the
    shell backtick operator). */
-string runProgram(const Path& program, bool searchPath = false,
-                  const Strings& args = Strings(),
-                  const std::optional<std::string>& input = {});
+std::string runProgram(const Path& program, bool searchPath = false,
+                       const Strings& args = Strings(),
+                       const std::optional<std::string>& input = {});
 
 struct RunOptions {
   std::optional<uid_t> uid;
@@ -292,7 +292,7 @@ std::vector<char*> stringsToCharPtrs(const Strings& ss);
 
 /* Close all file descriptors except those listed in the given set.
    Good practice in child processes. */
-void closeMostFDs(const set<int>& exceptions);
+void closeMostFDs(const std::set<int>& exceptions);
 
 /* Set the close-on-exec flag for the given file descriptor. */
 void closeOnExec(int fd);
@@ -311,36 +311,38 @@ void inline checkInterrupt() {
   if (_isInterrupted || (interruptCheck && interruptCheck())) _interrupted();
 }
 
-MakeError(Interrupted, BaseError)
+MakeError(Interrupted, BaseError);
 
-    MakeError(FormatError, Error)
+MakeError(FormatError, Error);
 
-    /* String tokenizer. */
-    template <class C>
-    C tokenizeString(const string& s, const string& separators = " \t\n\r");
+/* String tokenizer. */
+template <class C>
+C tokenizeString(const std::string& s,
+                 const std::string& separators = " \t\n\r");
 
 /* Concatenate the given strings with a separator between the
    elements. */
-string concatStringsSep(const string& sep, const Strings& ss);
-string concatStringsSep(const string& sep, const StringSet& ss);
+std::string concatStringsSep(const std::string& sep, const Strings& ss);
+std::string concatStringsSep(const std::string& sep, const StringSet& ss);
 
 /* Remove whitespace from the start and end of a string. */
-string trim(const string& s, const string& whitespace = " \n\r\t");
+std::string trim(const std::string& s,
+                 const std::string& whitespace = " \n\r\t");
 
 /* Replace all occurrences of a string inside another string. */
-string replaceStrings(const std::string& s, const std::string& from,
-                      const std::string& to);
+std::string replaceStrings(const std::string& s, const std::string& from,
+                           const std::string& to);
 
 /* Convert the exit status of a child as returned by wait() into an
    error string. */
-string statusToString(int status);
+std::string statusToString(int status);
 
 bool statusOk(int status);
 
 /* Parse a string into an integer. */
 template <class N>
-bool string2Int(const string& s, N& n) {
-  if (string(s, 0, 1) == "-" && !std::numeric_limits<N>::is_signed)
+bool string2Int(const std::string& s, N& n) {
+  if (std::string(s, 0, 1) == "-" && !std::numeric_limits<N>::is_signed)
     return false;
   std::istringstream str(s);
   str >> n;
@@ -349,17 +351,17 @@ bool string2Int(const string& s, N& n) {
 
 /* Parse a string into a float. */
 template <class N>
-bool string2Float(const string& s, N& n) {
+bool string2Float(const std::string& s, N& n) {
   std::istringstream str(s);
   str >> n;
   return str && str.get() == EOF;
 }
 
 /* Return true iff `s' starts with `prefix'. */
-bool hasPrefix(const string& s, const string& prefix);
+bool hasPrefix(const std::string& s, const std::string& prefix);
 
 /* Return true iff `s' ends in `suffix'. */
-bool hasSuffix(const string& s, const string& suffix);
+bool hasSuffix(const std::string& s, const std::string& suffix);
 
 /* Convert a string to lower case. */
 std::string toLower(const std::string& s);
@@ -389,13 +391,14 @@ std::string filterANSIEscapes(
     unsigned int width = std::numeric_limits<unsigned int>::max());
 
 /* Base64 encoding/decoding. */
-string base64Encode(const string& s);
-string base64Decode(const string& s);
+std::string base64Encode(const std::string& s);
+std::string base64Decode(const std::string& s);
 
 /* Get a value for the specified key from an associate container, or a
    default value if the key doesn't exist. */
 template <class T>
-string get(const T& map, const string& key, const string& def = "") {
+std::string get(const T& map, const std::string& key,
+                const std::string& def = "") {
   auto i = map.find(key);
   return i == map.end() ? def : i->second;
 }
diff --git a/third_party/nix/src/libutil/xml-writer.cc b/third_party/nix/src/libutil/xml-writer.cc
index 11cd632399ad..d34e9a2f0d59 100644
--- a/third_party/nix/src/libutil/xml-writer.cc
+++ b/third_party/nix/src/libutil/xml-writer.cc
@@ -26,10 +26,10 @@ void XMLWriter::indent_(size_t depth) {
   if (!indent) {
     return;
   }
-  output << string(depth * 2, ' ');
+  output << std::string(depth * 2, ' ');
 }
 
-void XMLWriter::openElement(const string& name, const XMLAttrs& attrs) {
+void XMLWriter::openElement(const std::string& name, const XMLAttrs& attrs) {
   assert(!closed);
   indent_(pendingElems.size());
   output << "<" << name;
@@ -54,7 +54,8 @@ void XMLWriter::closeElement() {
   }
 }
 
-void XMLWriter::writeEmptyElement(const string& name, const XMLAttrs& attrs) {
+void XMLWriter::writeEmptyElement(const std::string& name,
+                                  const XMLAttrs& attrs) {
   assert(!closed);
   indent_(pendingElems.size());
   output << "<" << name;
diff --git a/third_party/nix/src/libutil/xml-writer.hh b/third_party/nix/src/libutil/xml-writer.hh
index 3a2d9a66d8e1..76f3c7e3a2f4 100644
--- a/third_party/nix/src/libutil/xml-writer.hh
+++ b/third_party/nix/src/libutil/xml-writer.hh
@@ -11,7 +11,7 @@ using std::list;
 using std::map;
 using std::string;
 
-typedef map<string, string> XMLAttrs;
+typedef map<std::string, std::string> XMLAttrs;
 
 class XMLWriter {
  private:
@@ -20,7 +20,7 @@ class XMLWriter {
   bool indent;
   bool closed;
 
-  list<string> pendingElems;
+  std::list<std::string> pendingElems;
 
  public:
   XMLWriter(bool indent, std::ostream& output);
@@ -28,10 +28,10 @@ class XMLWriter {
 
   void close();
 
-  void openElement(const string& name, const XMLAttrs& attrs = XMLAttrs());
+  void openElement(const std::string& name, const XMLAttrs& attrs = XMLAttrs());
   void closeElement();
 
-  void writeEmptyElement(const string& name,
+  void writeEmptyElement(const std::string& name,
                          const XMLAttrs& attrs = XMLAttrs());
 
  private:
@@ -45,7 +45,7 @@ class XMLOpenElement {
   XMLWriter& writer;
 
  public:
-  XMLOpenElement(XMLWriter& writer, const string& name,
+  XMLOpenElement(XMLWriter& writer, const std::string& name,
                  const XMLAttrs& attrs = XMLAttrs())
       : writer(writer) {
     writer.openElement(name, attrs);