daemon: Remove ‘singleton’ and replace ‘typedef’ with ‘using’ in ‘types.hh’

* nix/libutil/util.hh (singleton): Remove.
* nix/libstore/build.cc (DerivationGoal::startBuilder)
(SubstitutionGoal::tryNext, SubstitutionGoal::tryToRun)
(LocalStore::ensurePath, LocalStore::repairPath): Use normal
construction function instead of ‘singleton’.
* nix/libstore/local-store.cc (LocalStore::addToStoreFromDump)
(LocalStore::addTextToStore, LocalStore::importPath): Likewise.
* nix/nix-daemon/nix-daemon.cc (performOp): Likewise.

Change-Id: If0d929407c09482f3b506a1c51dfda70e29696dd
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

nix/libutil/types.hh

@@ -76,24 +76,24 @@ public:
 };
 
 
-typedef list<string> Strings;
-typedef set<string> StringSet;
+using Strings = std::list<std::string>;
+using StringSet = std::set<std::string>;
 
 
 /* Paths are just strings. */
-typedef string Path;
-typedef list<Path> Paths;
-typedef set<Path> PathSet;
+using Path = std::string;
+using Paths = std::list<Path>;
+using PathSet = std::set<Path>;
 
 
-typedef enum {
+enum Verbosity {
     lvlError = 0,
     lvlInfo,
     lvlTalkative,
     lvlChatty,
     lvlDebug,
     lvlVomit
-} Verbosity;
+};
 
 
 }

nix/libutil/util.hh

@@ -121,15 +121,6 @@ Paths createDirs(const Path & path);
 void createSymlink(const Path & target, const Path & link);
 
 
-template<class T, class A>
-T singleton(const A & a)
-{
-    T t;
-    t.insert(a);
-    return t;
-}
-
-
 /* Messages. */