add has_value check; remove obslete friend class

src/libutil/error.cc

@@ -162,7 +162,7 @@ std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo)
     out << prefix << std::endl;
 
     // lines of code.
-    if (einfo.nixCode->errLineOfCode != "") {
+    if (einfo.nixCode.has_value() && einfo.nixCode->errLineOfCode != "") {
         printCodeLines(prefix, *einfo.nixCode);
         out << prefix << std::endl;
     }

src/libutil/fmt.hh

@@ -92,9 +92,11 @@ public:
     {
         fmt.exceptions(boost::io::all_error_bits ^ boost::io::too_many_args_bit);
     }
+
     hintformat(const hintformat &hf)
     : fmt(hf.fmt)
     {}
+
     template<class T>
     hintformat& operator%(const T &value)
     {
@@ -102,14 +104,11 @@ public:
         return *this;
     }
 
-
     std::string str() const
     {
         return fmt.str();
     }
 
-    template <typename U>
-    friend class AddHint;
 private:
     format fmt;
 };

src/libutil/logging.hh

@@ -62,11 +62,12 @@ public:
 
     virtual void logEI(const ErrorInfo &ei) = 0;
 
-    void logEI(Verbosity lvl, ErrorInfo ei) {
-      ei.level = lvl;
-      logEI(ei);
+    void logEI(Verbosity lvl, ErrorInfo ei) 
+    {
+        ei.level = lvl;
+        logEI(ei);
     }
-
+    
     virtual void warn(const std::string & msg);
 
     virtual void startActivity(ActivityId act, Verbosity lvl, ActivityType type,