diff --git a/src/error-demo/error-demo.cc b/src/error-demo/error-demo.cc
index 8fb20d38c..a9ff6057c 100644
--- a/src/error-demo/error-demo.cc
+++ b/src/error-demo/error-demo.cc
@@ -11,77 +11,56 @@ int main()
     // In each program where errors occur, this has to be set.
     ErrorInfo::programName = std::optional("error-demo");
 
-    // There are currently four error types:
-    //
-    // 			ProgramError, ProgramWarning, NixLangError, NixLangWarning.
-    //
-    // Each error type is created with a specific sequence of builder functions.
-    // Unlike with a constructor, each parameter is clearly named.
-    // If the sequence of function calls isn't followed, then there's a type
-    // error. This should make for a consistent look in the code when errors are
-    // created.
+    // Error in a program; no hint and no nix code.
+    printErrorInfo(
+        ErrorInfo { .level = elError,
+                    .name = "name",
+                    .description = "error description",
+                  });
 
-    // ProgramError takes name, description, and an optional hint.
-    printErrorInfo( ProgramError()
-                    .name("name")
-                    .description("error description")
-                    .nohint()
-                  );
+    // Warning with name, description, and hint.
+    // The hintfmt function makes all the substituted text yellow.
+    printErrorInfo(
+        ErrorInfo { .level = elWarning,
+                    .name = "name",
+                    .description = "error description",
+                    .hint =  std::optional(
+                                 hintfmt("there was a %1%", "warning")),
+                  });
 
-    // ProgramWarning takes name, description, and an optional hint.
-    // The hint is in the form of a hintfmt class, which wraps boost::format(),
-    // and makes all the substituted text yellow.
-    printErrorInfo( ProgramWarning()
-                    .name("warning name")
-                    .description("warning description")
-                    // the templated value, 'warning', is automatically colored yellow.
-                    .hint(hintfmt("there was a %1%", "warning")) 
-                  );
 
-    /*
-      // some invalid errors:
-
-      // type error: no hint function.
-      ProgramError()
-        .name("name")
-        .description("error description");
-
-      // type error:  description before name.
-      ProgramError()
-        .description("error description")
-        .name("name")
-        .nohint();
-
-      // type error: hint function with regular boost format, not special
-      hintfmt. ProgramError() .description("error description") .name("name")
-        .hint(format("there was a %1%") % "warning");
-    */
-
-    // NixLangWarning adds nix file, line number, column range, and the lines of
+    // Warning with nix file, line number, column, and the lines of
     // code where a warning occurred.
-
     SymbolTable testTable;
-    auto problem_symbol = testTable.create("problem");
+    auto problem_file = testTable.create("myfile.nix");
 
-    printErrorInfo(NixLangWarning()
-                   .name("warning name")
-                   .description("warning description")
-                   .pos(Pos(problem_symbol, 40, 13))
-                   .linesOfCode(std::nullopt,
-                                "this is the problem line of code",
-                                std::nullopt)
-                   .hint(hintfmt("this hint has %1% templated %2%!!", "yellow" , "values")));
+    printErrorInfo(
+        ErrorInfo{
+            .level = elWarning,
+            .name = "warning name",
+            .description = "warning description",
+            .hint = hintfmt("this hint has %1% templated %2%!!", "yellow", "values"),
+            .nixCode = NixCode {
+                .errPos = Pos(problem_file, 40, 13),
+                .prevLineOfCode = std::nullopt,
+                .errLineOfCode = "this is the problem line of code",
+                .nextLineOfCode = std::nullopt
+            }});
+
+    // Error with previous and next lines of code.
+    printErrorInfo(
+        ErrorInfo{
+            .level = elError,
+            .name = "error name",
+            .description = "error description",
+            .hint = hintfmt("this hint has %1% templated %2%!!", "yellow", "values"),
+            .nixCode = NixCode {
+                .errPos = Pos(problem_file, 40, 13),
+                .prevLineOfCode = std::optional("previous line of code"),
+                .errLineOfCode = "this is the problem line of code",
+                .nextLineOfCode = std::optional("next line of code"),
+            }});
 
-    // NixLangError is just the same as NixLangWarning, except for the Error
-    // flag.
-    printErrorInfo(NixLangError()
-                   .name("error name")
-                   .description("error description")
-                   .pos(Pos(problem_symbol, 40, 13))
-                   .linesOfCode(std::optional("previous line of code"),
-                                "this is the problem line of code",
-                                std::optional("next line of code"))
-                   .hint(hintfmt("this hint has %1% templated %2%!!", "yellow", "values")));
 
     return 0;
 }
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 106ea127e..40354cc87 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -8,68 +8,60 @@ namespace nix
 
 std::optional<string> ErrorInfo::programName = std::nullopt;
 
-string showErrLine(ErrLine &errLine)
+string showErrPos(const ErrPos &errPos)
 {
-    if (errLine.column > 0) {
-        return fmt("(%1%:%2%)", errLine.lineNumber, errLine.column);
+    if (errPos.column > 0) {
+        return fmt("(%1%:%2%)", errPos.lineNumber, errPos.column);
     } else {
-        return fmt("(%1%)", errLine.lineNumber);
+        return fmt("(%1%)", errPos.lineNumber);
     };
 }
 
-void printCodeLines(string &prefix, NixCode &nixCode)
+void printCodeLines(const string &prefix, const NixCode &nixCode)
 {
-
-    if (nixCode.errLine.has_value()) {
-        // previous line of code.
-        if (nixCode.errLine->prevLineOfCode.has_value()) {
-            std::cout << fmt("%1% %|2$5d|| %3%",
-                             prefix,
-                             (nixCode.errLine->lineNumber - 1),
-                             *nixCode.errLine->prevLineOfCode)
-                      << std::endl;
-        }
-
-        // line of code containing the error.%2$+5d%
+    // previous line of code.
+    if (nixCode.prevLineOfCode.has_value()) {
         std::cout << fmt("%1% %|2$5d|| %3%",
                          prefix,
-                         (nixCode.errLine->lineNumber),
-                         nixCode.errLine->errLineOfCode)
+                         (nixCode.errPos.lineNumber - 1),
+                         *nixCode.prevLineOfCode)
                   << std::endl;
-
-        // error arrows for the column range.
-        if (nixCode.errLine->column > 0) {
-            int start = nixCode.errLine->column;
-            std::string spaces;
-            for (int i = 0; i < start; ++i) {
-                spaces.append(" ");
-            }
-
-            // for now, length of 1.
-            std::string arrows("^");
-
-            std::cout << fmt("%1%      |%2%" ANSI_RED "%3%" ANSI_NORMAL,
-                             prefix,
-                             spaces,
-                             arrows) << std::endl;
-        }
-
-
-
-        // next line of code.
-        if (nixCode.errLine->nextLineOfCode.has_value()) {
-            std::cout << fmt("%1% %|2$5d|| %3%",
-                             prefix,
-                             (nixCode.errLine->lineNumber + 1),
-                             *nixCode.errLine->nextLineOfCode)
-                      << std::endl;
-        }
-
     }
 
+    // line of code containing the error.%2$+5d%
+    std::cout << fmt("%1% %|2$5d|| %3%",
+                     prefix,
+                     (nixCode.errPos.lineNumber),
+                     nixCode.errLineOfCode)
+              << std::endl;
+
+    // error arrows for the column range.
+    if (nixCode.errPos.column > 0) {
+        int start = nixCode.errPos.column;
+        std::string spaces;
+        for (int i = 0; i < start; ++i) {
+            spaces.append(" ");
+        }
+
+        std::string arrows("^");
+
+        std::cout << fmt("%1%      |%2%" ANSI_RED "%3%" ANSI_NORMAL,
+                         prefix,
+                         spaces,
+                         arrows) << std::endl;
+    }
+
+    // next line of code.
+    if (nixCode.nextLineOfCode.has_value()) {
+        std::cout << fmt("%1% %|2$5d|| %3%",
+                         prefix,
+                         (nixCode.errPos.lineNumber + 1),
+                         *nixCode.nextLineOfCode)
+                  << std::endl;
+    }
 }
 
-void printErrorInfo(ErrorInfo &einfo)
+void printErrorInfo(const ErrorInfo &einfo)
 {
     int errwidth = 80;
     string prefix = "    ";
@@ -102,24 +94,26 @@ void printErrorInfo(ErrorInfo &einfo)
         dashes.append("-");
 
     // divider.
-    std::cout << fmt("%1%%2%" ANSI_BLUE " %3% %4% %5% %6%" ANSI_NORMAL
-                     , prefix
-                     , levelString
-                     , "---"
-                     , einfo.name
-                     , dashes
-                     , einfo.programName.value_or(""))
+    std::cout << fmt("%1%%2%" ANSI_BLUE " %3% %4% %5% %6%" ANSI_NORMAL,
+                     prefix,
+                     levelString,
+                     "---",
+                     einfo.name,
+                     dashes,
+                     einfo.programName.value_or(""))
               << std::endl;
 
     // filename.
     if (einfo.nixCode.has_value()) {
-        if (einfo.nixCode->nixFile.has_value()) {
-            string eline = einfo.nixCode->errLine.has_value()
-                           ? string(" ") + showErrLine(*einfo.nixCode->errLine)
+        if (einfo.nixCode->errPos.nixFile != "") {
+            string eline = einfo.nixCode->errLineOfCode != ""
+                           ? string(" ") + showErrPos(einfo.nixCode->errPos)
                            : "";
 
-            std::cout << fmt("%1%in file: " ANSI_BLUE "%2%%3%" ANSI_NORMAL
-                             , prefix, *einfo.nixCode->nixFile, eline) << std::endl;
+            std::cout << fmt("%1%in file: " ANSI_BLUE "%2%%3%" ANSI_NORMAL,
+                             prefix, 
+                             einfo.nixCode->errPos.nixFile,
+                             eline) << std::endl;
             std::cout << prefix << std::endl;
         } else {
             std::cout << fmt("%1%from command line argument", prefix) << std::endl;
@@ -132,7 +126,7 @@ void printErrorInfo(ErrorInfo &einfo)
     std::cout << prefix << std::endl;
 
     // lines of code.
-    if (einfo.nixCode.has_value()) {
+    if (einfo.nixCode->errLineOfCode != "") {
         printCodeLines(prefix, *einfo.nixCode);
         std::cout << prefix << std::endl;
     }
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 664bfbb5a..8286eaab1 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -17,172 +17,40 @@ typedef enum {
     elError
 } ErrLevel;
 
-class ErrorInfo;
-
-class ErrLine
+class ErrPos
 {
 public:
     int lineNumber;
     int column;
-    std::optional<string> prevLineOfCode;
-    string errLineOfCode;
-    std::optional<string> nextLineOfCode;
+    string nixFile;
+
+    template <class P>
+    ErrPos& operator=(const P &pos)
+    {
+        lineNumber = pos.line;
+        column = pos.column;
+        nixFile = pos.file;
+        return *this;
+    }
+
+    template <class P>
+    ErrPos(const P &p)
+    {
+      *this = p;
+    }
 };
 
 class NixCode
 {
 public:
-    std::optional<string> nixFile;
-    std::optional<ErrLine> errLine;
-
-    ErrLine& ensureErrLine()
-    {
-        if (!this->errLine.has_value())
-            this->errLine = std::optional(ErrLine());
-        return *this->errLine;
-    }
+    ErrPos errPos;
+    std::optional<string> prevLineOfCode;
+    string errLineOfCode;
+    std::optional<string> nextLineOfCode;
 };
 
-// -------------------------------------------------
-// ErrorInfo.
-
-// Forward friend class declarations.    "builder classes"
-template <class T>
-class AddName;
-
-template <class T>
-class AddDescription;
-
-template <class T>
-class AddPos;
-
-template <class T>
-class AddLOC;
-
-// The error info class itself.
-class ErrorInfo
-{
-public:
-    ErrLevel level;
-    string name;
-    string description;
-    std::optional<NixCode> nixCode;
-    std::optional<string> hint;
-    ErrorInfo& GetEI()
-    {
-        return *this;
-    }
-
-    static std::optional<string> programName;
-
-    // give these access to the private constructor,
-    // when they are direct descendants (children but not grandchildren).
-    friend AddName<ErrorInfo>;
-    friend AddDescription<ErrorInfo>;
-    friend AddPos<ErrorInfo>;
-    friend AddLOC<ErrorInfo>;
-
-    NixCode& ensureNixCode()
-    {
-        if (!this->nixCode.has_value())
-            this->nixCode = std::optional(NixCode());
-        return *this->nixCode;
-    }
-protected:
-    // constructor is protected, so only the builder classes can create an ErrorInfo.
-    ErrorInfo(ErrLevel level)
-    {
-        this->level = level;
-    }
-};
-
-// Init as error
-class EIError : public ErrorInfo
-{
-protected:
-    EIError() : ErrorInfo(elError) {}
-};
-
-// Init as warning
-class EIWarning : public ErrorInfo
-{
-protected:
-    EIWarning() : ErrorInfo(elWarning) {}
-};
-
-// Builder class definitions.
-template <class T>
-class AddName : private T
-{
-public:
-    T& name(const std::string &name)
-    {
-        GetEI().name = name;
-        return *this;
-    }
-protected:
-    ErrorInfo& GetEI()
-    {
-        return T::GetEI();
-    }
-};
-
-template <class T>
-class AddDescription : private T
-{
-public:
-    T& description(const std::string &description)
-    {
-        GetEI().description = description;
-        return *this;
-    }
-protected:
-    ErrorInfo& GetEI()
-    {
-        return T::GetEI();
-    }
-};
-
-template <class T>
-class AddPos : private T
-{
-public:
-    template <class P>
-    T& pos(const P &aPos)
-    {
-        GetEI().ensureNixCode().nixFile = aPos.file;
-        GetEI().ensureNixCode().ensureErrLine().lineNumber = aPos.line;
-        GetEI().ensureNixCode().ensureErrLine().column = aPos.column;
-        return *this;
-    }
-protected:
-    ErrorInfo& GetEI()
-    {
-        return T::GetEI();
-    }
-};
-
-template <class T>
-class AddLOC : private T
-{
-public:
-    T& linesOfCode(std::optional<string> prevloc, string loc, std::optional<string> nextloc)
-    {
-        GetEI().ensureNixCode().ensureErrLine().prevLineOfCode = prevloc;
-        GetEI().ensureNixCode().ensureErrLine().errLineOfCode = loc;
-        GetEI().ensureNixCode().ensureErrLine().nextLineOfCode = nextloc;
-        return *this;
-    }
-protected:
-    ErrorInfo& GetEI()
-    {
-        return T::GetEI();
-    }
-};
-
-
 // ----------------------------------------------------------------
-// format for hints.  same as fmt, except templated values
+// format function for hints.  same as fmt, except templated values
 // are always in yellow.
 
 template <class T>
@@ -222,9 +90,13 @@ public:
     friend class AddHint;
 private:
     format fmt;
-
 };
 
+std::ostream& operator<<(std::ostream &os, const hintformat &hf)
+{
+    return os << hf.str();
+}
+
 template<typename... Args>
 inline hintformat hintfmt(const std::string & fs, const Args & ... args)
 {
@@ -233,61 +105,27 @@ inline hintformat hintfmt(const std::string & fs, const Args & ... args)
     return f;
 }
 
-// the template layer for adding a hint.
-template <class T>
-class AddHint : private T
+// -------------------------------------------------
+// ErrorInfo.
+class ErrorInfo
 {
 public:
-    T& hint(const hintformat &hf)
-    {
-        GetEI().hint = std::optional(hf.str());
-        return *this;
-    }
-    T& nohint()
-    {
-        GetEI().hint = std::nullopt;
-        return *this;
-    }
-protected:
-    ErrorInfo& GetEI()
-    {
-        return T::GetEI();
-    }
+    ErrLevel level;
+    string name;
+    string description;
+    std::optional<hintformat> hint;
+    std::optional<NixCode> nixCode;
+
+    static std::optional<string> programName;
+
+private:
 };
 
-// --------------------------------------------------------
-// error types
-
-typedef AddName<
-        AddDescription<
-        AddHint<
-        EIError>>> ProgramError;
-
-typedef AddName<
-        AddDescription<
-        AddHint<
-        EIWarning>>> ProgramWarning;
-
-typedef AddName<
-        AddDescription<
-        AddPos<
-        AddLOC<
-        AddHint<
-        EIError>>>>> NixLangError;
-
-typedef AddName<
-        AddDescription<
-        AddPos<
-        AddLOC<
-        AddHint<
-        EIWarning>>>>> NixLangWarning;
-
-
 // --------------------------------------------------------
 // error printing
 
 // just to cout for now.
-void printErrorInfo(ErrorInfo &einfo);
+void printErrorInfo(const ErrorInfo &einfo);
 
 }