diff --git a/src/libexpr/attr-set.hh b/src/libexpr/attr-set.hh
index c601d09c2..7eaa16c59 100644
--- a/src/libexpr/attr-set.hh
+++ b/src/libexpr/attr-set.hh
@@ -78,7 +78,7 @@ public:
         if (!a)
             throw Error({
                 .hint = hintfmt("attribute '%s' missing", name),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
         return *a;
diff --git a/src/libexpr/eval-inline.hh b/src/libexpr/eval-inline.hh
index 3d544c903..30f6ec7db 100644
--- a/src/libexpr/eval-inline.hh
+++ b/src/libexpr/eval-inline.hh
@@ -11,7 +11,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s))
 {
     throw EvalError({
         .hint = hintfmt(s),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -25,7 +25,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
 {
     throw TypeError({
         .hint = hintfmt(s, showType(v)),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index c249add86..3fd8aa285 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -529,7 +529,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
 {
     throw EvalError({
         .hint = hintfmt(s, s2),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -542,7 +542,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
 {
     throw EvalError({
         .hint = hintfmt(s, s2, s3),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -551,7 +551,7 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & p1, const char * s, const
     // p1 is where the error occurred; p2 is a position mentioned in the message.
     throw EvalError({
         .hint = hintfmt(s, sym, p2),
-        .nixCode = NixCode { .errPos = p1 }
+        .errPos = p1
     });
 }
 
@@ -559,7 +559,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s))
 {
     throw TypeError({
         .hint = hintfmt(s),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -572,7 +572,7 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
 {
     throw TypeError({
         .hint = hintfmt(s, fun.showNamePos(), s2),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -580,7 +580,7 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
 {
     throw AssertionError({
         .hint = hintfmt(s, s1),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -588,7 +588,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
 {
     throw UndefinedVarError({
         .hint = hintfmt(s, s1),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
@@ -1938,7 +1938,7 @@ string ExternalValueBase::coerceToString(const Pos & pos, PathSet & context, boo
 {
     throw TypeError({
         .hint = hintfmt("cannot coerce %1% to a string", showType()),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index d4e179008..2b22ef3b6 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -285,7 +285,7 @@ void ExprVar::bindVars(const StaticEnv & env)
     if (withLevel == -1)
         throw UndefinedVarError({
             .hint = hintfmt("undefined variable '%1%'", name),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     fromWith = true;
     this->level = withLevel;
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index b1bf9f67b..e4cbc660f 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -239,7 +239,7 @@ struct ExprLambda : Expr
         if (!arg.empty() && formals && formals->argNames.find(arg) != formals->argNames.end())
             throw ParseError({
                 .hint = hintfmt("duplicate formal function argument '%1%'", arg),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
     };
     void setName(Symbol & name);
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index b746e70af..472b33c2f 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -66,18 +66,17 @@ namespace nix {
 static void dupAttr(const AttrPath & attrPath, const Pos & pos, const Pos & prevPos)
 {
     throw ParseError({
-        .hint = hintfmt("attribute '%1%' already defined at %2%",
+         .hint = hintfmt("attribute '%1%' already defined at %2%",
             showAttrPath(attrPath), prevPos),
-        .nixCode = NixCode { .errPos = pos },
+         .errPos = pos
     });
 }
 
-
 static void dupAttr(Symbol attr, const Pos & pos, const Pos & prevPos)
 {
     throw ParseError({
         .hint = hintfmt("attribute '%1%' already defined at %2%", attr, prevPos),
-        .nixCode = NixCode { .errPos = pos },
+        .errPos = pos
     });
 }
 
@@ -149,7 +148,7 @@ static void addFormal(const Pos & pos, Formals * formals, const Formal & formal)
         throw ParseError({
             .hint = hintfmt("duplicate formal function argument '%1%'",
                 formal.name),
-            .nixCode = NixCode { .errPos = pos },
+            .errPos = pos
         });
     formals->formals.push_front(formal);
 }
@@ -260,7 +259,7 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
 {
     data->error = {
         .hint = hintfmt(error),
-        .nixCode = NixCode { .errPos = makeCurPos(*loc, data) }
+        .errPos = makeCurPos(*loc, data)
     };
 }
 
@@ -340,7 +339,7 @@ expr_function
     { if (!$2->dynamicAttrs.empty())
         throw ParseError({
             .hint = hintfmt("dynamic attributes not allowed in let"),
-            .nixCode = NixCode { .errPos = CUR_POS },
+            .errPos = CUR_POS
         });
       $$ = new ExprLet($2, $4);
     }
@@ -420,7 +419,7 @@ expr_simple
       if (noURLLiterals)
           throw ParseError({
               .hint = hintfmt("URL literals are disabled"),
-              .nixCode = NixCode { .errPos = CUR_POS }
+              .errPos = CUR_POS
           });
       $$ = new ExprString(data->symbols.create($1));
   }
@@ -493,7 +492,7 @@ attrs
       } else
           throw ParseError({
               .hint = hintfmt("dynamic attributes not allowed in inherit"),
-              .nixCode = NixCode { .errPos = makeCurPos(@2, data) },
+              .errPos = makeCurPos(@2, data)
           });
     }
   | { $$ = new AttrPath; }
@@ -705,7 +704,7 @@ Path EvalState::findFile(SearchPath & searchPath, const string & path, const Pos
             ? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
             : "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
             path),
-        .nixCode = NixCode { .errPos = pos }
+        .errPos = pos
     });
 }
 
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 3f6bd7969..6f7a691cd 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -96,7 +96,7 @@ static void prim_scopedImport(EvalState & state, const Pos & pos, Value * * args
     } catch (InvalidPathError & e) {
         throw EvalError({
             .hint = hintfmt("cannot import '%1%', since path '%2%' is not valid", path, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 
@@ -177,7 +177,7 @@ void prim_importNative(EvalState & state, const Pos & pos, Value * * args, Value
             .hint = hintfmt(
                 "cannot import '%1%', since path '%2%' is not valid",
                 path, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 
@@ -215,7 +215,7 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
     if (count == 0) {
         throw EvalError({
             .hint = hintfmt("at least one argument to 'exec' required"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
     PathSet context;
@@ -230,7 +230,7 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
         throw EvalError({
             .hint = hintfmt("cannot execute '%1%', since path '%2%' is not valid",
                 program, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 
@@ -385,7 +385,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
     if (startSet == args[0]->attrs->end())
         throw EvalError({
             .hint = hintfmt("attribute 'startSet' required"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     state.forceList(*startSet->value, pos);
 
@@ -399,7 +399,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
     if (op == args[0]->attrs->end())
         throw EvalError({
             .hint = hintfmt("attribute 'operator' required"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     state.forceValue(*op->value, pos);
 
@@ -421,7 +421,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
         if (key == e->attrs->end())
             throw EvalError({
                 .hint = hintfmt("attribute 'key' required"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         state.forceValue(*key->value, pos);
 
@@ -557,7 +557,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
     if (attr == args[0]->attrs->end())
         throw EvalError({
             .hint = hintfmt("required attribute 'name' missing"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     string drvName;
     Pos & posDrvName(*attr->pos);
@@ -604,7 +604,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             else
                 throw EvalError({
                     .hint = hintfmt("invalid value '%s' for 'outputHashMode' attribute", s),
-                    .nixCode = NixCode { .errPos = posDrvName }
+                    .errPos = posDrvName
                 });
         };
 
@@ -614,7 +614,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
                 if (outputs.find(j) != outputs.end())
                     throw EvalError({
                         .hint = hintfmt("duplicate derivation output '%1%'", j),
-                        .nixCode = NixCode { .errPos = posDrvName }
+                        .errPos = posDrvName
                     });
                 /* !!! Check whether j is a valid attribute
                    name. */
@@ -624,14 +624,14 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
                 if (j == "drv")
                     throw EvalError({
                         .hint = hintfmt("invalid derivation output name 'drv'" ),
-                        .nixCode = NixCode { .errPos = posDrvName }
+                        .errPos = posDrvName
                     });
                 outputs.insert(j);
             }
             if (outputs.empty())
                 throw EvalError({
                     .hint = hintfmt("derivation cannot have an empty set of outputs"),
-                    .nixCode = NixCode { .errPos = posDrvName }
+                    .errPos = posDrvName
                 });
         };
 
@@ -747,20 +747,20 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
     if (drv.builder == "")
         throw EvalError({
             .hint = hintfmt("required attribute 'builder' missing"),
-            .nixCode = NixCode { .errPos = posDrvName }
+            .errPos = posDrvName
         });
 
     if (drv.platform == "")
         throw EvalError({
             .hint = hintfmt("required attribute 'system' missing"),
-            .nixCode = NixCode { .errPos = posDrvName }
+            .errPos = posDrvName
         });
 
     /* Check whether the derivation name is valid. */
     if (isDerivation(drvName))
         throw EvalError({
             .hint = hintfmt("derivation names are not allowed to end in '%s'", drvExtension),
-            .nixCode = NixCode { .errPos = posDrvName }
+            .errPos = posDrvName
         });
 
     if (outputHash) {
@@ -768,7 +768,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
         if (outputs.size() != 1 || *(outputs.begin()) != "out")
             throw Error({
                 .hint = hintfmt("multiple outputs are not supported in fixed-output derivations"),
-                .nixCode = NixCode { .errPos = posDrvName }
+                .errPos = posDrvName
             });
 
         std::optional<HashType> ht = parseHashTypeOpt(outputHashAlgo);
@@ -882,7 +882,7 @@ static void prim_storePath(EvalState & state, const Pos & pos, Value * * args, V
     if (!state.store->isInStore(path))
         throw EvalError({
             .hint = hintfmt("path '%1%' is not in the Nix store", path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     Path path2 = state.store->toStorePath(path);
     if (!settings.readOnlyMode)
@@ -903,7 +903,7 @@ static void prim_pathExists(EvalState & state, const Pos & pos, Value * * args,
             .hint = hintfmt(
                 "cannot check the existence of '%1%', since path '%2%' is not valid",
                 path, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 
@@ -949,7 +949,7 @@ static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Va
     } catch (InvalidPathError & e) {
         throw EvalError({
             .hint = hintfmt("cannot read '%1%', since path '%2%' is not valid", path, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
     string s = readFile(state.checkSourcePath(state.toRealPath(path, context)));
@@ -980,7 +980,7 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
         if (i == v2.attrs->end())
             throw EvalError({
                 .hint = hintfmt("attribute 'path' missing"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
         PathSet context;
@@ -991,7 +991,7 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
         } catch (InvalidPathError & e) {
             throw EvalError({
                 .hint = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         }
 
@@ -1011,7 +1011,7 @@ static void prim_hashFile(EvalState & state, const Pos & pos, Value * * args, Va
     if (!ht)
       throw Error({
           .hint = hintfmt("unknown hash type '%1%'", type),
-          .nixCode = NixCode { .errPos = pos }
+          .errPos = pos
       });
 
     PathSet context; // discarded
@@ -1030,7 +1030,7 @@ static void prim_readDir(EvalState & state, const Pos & pos, Value * * args, Val
     } catch (InvalidPathError & e) {
         throw EvalError({
             .hint = hintfmt("cannot read '%1%', since path '%2%' is not valid", path, e.path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 
@@ -1106,7 +1106,7 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
                     "in 'toFile': the file named '%1%' must not contain a reference "
                     "to a derivation but contains (%2%)",
                     name, path),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         refs.insert(state.store->parseStorePath(path));
     }
@@ -1177,7 +1177,7 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
     if (!context.empty())
         throw EvalError({
             .hint = hintfmt("string '%1%' cannot refer to other paths", path),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     state.forceValue(*args[0], pos);
@@ -1186,7 +1186,7 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
             .hint = hintfmt(
                 "first argument in call to 'filterSource' is not a function but %1%",
                 showType(*args[0])),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     addPath(state, pos, std::string(baseNameOf(path)), path, args[0], FileIngestionMethod::Recursive, Hash(), v);
@@ -1209,7 +1209,7 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
             if (!context.empty())
                 throw EvalError({
                     .hint = hintfmt("string '%1%' cannot refer to other paths", path),
-                    .nixCode = NixCode { .errPos = *attr.pos }
+                    .errPos = *attr.pos
                 });
         } else if (attr.name == state.sName)
             name = state.forceStringNoCtx(*attr.value, *attr.pos);
@@ -1223,13 +1223,13 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
         else
             throw EvalError({
                 .hint = hintfmt("unsupported argument '%1%' to 'addPath'", attr.name),
-                .nixCode = NixCode { .errPos = *attr.pos }
+                .errPos = *attr.pos
             });
     }
     if (path.empty())
         throw EvalError({
             .hint = hintfmt("'path' required"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     if (name.empty())
         name = baseNameOf(path);
@@ -1290,7 +1290,7 @@ void prim_getAttr(EvalState & state, const Pos & pos, Value * * args, Value & v)
     if (i == args[1]->attrs->end())
         throw EvalError({
             .hint = hintfmt("attribute '%1%' missing", attr),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     // !!! add to stack trace?
     if (state.countCalls && i->pos) state.attrSelects[*i->pos]++;
@@ -1373,7 +1373,7 @@ static void prim_listToAttrs(EvalState & state, const Pos & pos, Value * * args,
         if (j == v2.attrs->end())
             throw TypeError({
                 .hint = hintfmt("'name' attribute missing in a call to 'listToAttrs'"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         string name = state.forceStringNoCtx(*j->value, pos);
 
@@ -1383,7 +1383,7 @@ static void prim_listToAttrs(EvalState & state, const Pos & pos, Value * * args,
             if (j2 == v2.attrs->end())
                 throw TypeError({
                     .hint = hintfmt("'value' attribute missing in a call to 'listToAttrs'"),
-                    .nixCode = NixCode { .errPos = pos }
+                    .errPos = pos
                 });
             v.attrs->push_back(Attr(sym, j2->value, j2->pos));
         }
@@ -1459,7 +1459,7 @@ static void prim_functionArgs(EvalState & state, const Pos & pos, Value * * args
     if (args[0]->type != tLambda)
         throw TypeError({
             .hint = hintfmt("'functionArgs' requires a function"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     if (!args[0]->lambda.fun->matchAttrs) {
@@ -1515,7 +1515,7 @@ static void elemAt(EvalState & state, const Pos & pos, Value & list, int n, Valu
     if (n < 0 || (unsigned int) n >= list.listSize())
         throw Error({
             .hint = hintfmt("list index %1% is out of bounds", n),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     state.forceValue(*list.listElems()[n], pos);
     v = *list.listElems()[n];
@@ -1545,7 +1545,7 @@ static void prim_tail(EvalState & state, const Pos & pos, Value * * args, Value
     if (args[0]->listSize() == 0)
         throw Error({
             .hint = hintfmt("'tail' called on an empty list"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     state.mkList(v, args[0]->listSize() - 1);
@@ -1690,7 +1690,7 @@ static void prim_genList(EvalState & state, const Pos & pos, Value * * args, Val
     if (len < 0)
         throw EvalError({
             .hint = hintfmt("cannot create list of size %1%", len),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     state.mkList(v, len);
@@ -1852,7 +1852,7 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
     if (f2 == 0)
         throw EvalError({
             .hint = hintfmt("division by zero"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     if (args[0]->type == tFloat || args[1]->type == tFloat) {
@@ -1864,7 +1864,7 @@ static void prim_div(EvalState & state, const Pos & pos, Value * * args, Value &
         if (i1 == std::numeric_limits<NixInt>::min() && i2 == -1)
             throw EvalError({
                 .hint = hintfmt("overflow in integer division"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
         mkInt(v, i1 / i2);
@@ -1925,7 +1925,7 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
     if (start < 0)
         throw EvalError({
             .hint = hintfmt("negative start position in 'substring'"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     mkString(v, (unsigned int) start >= s.size() ? "" : string(s, start, len), context);
@@ -1948,7 +1948,7 @@ static void prim_hashString(EvalState & state, const Pos & pos, Value * * args,
     if (!ht)
         throw Error({
             .hint = hintfmt("unknown hash type '%1%'", type),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     PathSet context; // discarded
@@ -1994,12 +1994,12 @@ void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v)
             // limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
             throw EvalError({
                 .hint = hintfmt("memory limit exceeded by regular expression '%s'", re),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         } else {
             throw EvalError({
                 .hint = hintfmt("invalid regular expression '%s'", re),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         }
     }
@@ -2067,12 +2067,12 @@ static void prim_split(EvalState & state, const Pos & pos, Value * * args, Value
             // limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
             throw EvalError({
                 .hint = hintfmt("memory limit exceeded by regular expression '%s'", re),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         } else {
             throw EvalError({
                 .hint = hintfmt("invalid regular expression '%s'", re),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
         }
     }
@@ -2106,7 +2106,7 @@ static void prim_replaceStrings(EvalState & state, const Pos & pos, Value * * ar
     if (args[0]->listSize() != args[1]->listSize())
         throw EvalError({
             .hint = hintfmt("'from' and 'to' arguments to 'replaceStrings' have different lengths"),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
 
     vector<string> from;
diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index 301e8c5dd..dbb93bae6 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -148,7 +148,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
         if (!state.store->isStorePath(i.name))
             throw EvalError({
                 .hint = hintfmt("Context key '%s' is not a store path", i.name),
-                .nixCode = NixCode { .errPos = *i.pos }
+                .errPos = *i.pos
             });
         if (!settings.readOnlyMode)
             state.store->ensurePath(state.store->parseStorePath(i.name));
@@ -165,7 +165,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
                 if (!isDerivation(i.name)) {
                     throw EvalError({
                         .hint = hintfmt("Tried to add all-outputs context of %s, which is not a derivation, to a string", i.name),
-                        .nixCode = NixCode { .errPos = *i.pos }
+                        .errPos = *i.pos
                     });
                 }
                 context.insert("=" + string(i.name));
@@ -178,7 +178,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
             if (iter->value->listSize() && !isDerivation(i.name)) {
                 throw EvalError({
                     .hint = hintfmt("Tried to add derivation output context of %s, which is not a derivation, to a string", i.name),
-                    .nixCode = NixCode { .errPos = *i.pos }
+                    .errPos = *i.pos
                 });
             }
             for (unsigned int n = 0; n < iter->value->listSize(); ++n) {
diff --git a/src/libexpr/primops/fetchGit.cc b/src/libexpr/primops/fetchGit.cc
index dd7229a3d..36b0db2bd 100644
--- a/src/libexpr/primops/fetchGit.cc
+++ b/src/libexpr/primops/fetchGit.cc
@@ -37,14 +37,14 @@ static void prim_fetchGit(EvalState & state, const Pos & pos, Value * * args, Va
             else
                 throw EvalError({
                     .hint = hintfmt("unsupported argument '%s' to 'fetchGit'", attr.name),
-                    .nixCode = NixCode { .errPos = *attr.pos }
+                    .errPos = *attr.pos
                 });
         }
 
         if (url.empty())
             throw EvalError({
                 .hint = hintfmt("'url' argument required"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
     } else
diff --git a/src/libexpr/primops/fetchMercurial.cc b/src/libexpr/primops/fetchMercurial.cc
index 9bace8f89..59166b777 100644
--- a/src/libexpr/primops/fetchMercurial.cc
+++ b/src/libexpr/primops/fetchMercurial.cc
@@ -40,14 +40,14 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
             else
                 throw EvalError({
                     .hint = hintfmt("unsupported argument '%s' to 'fetchMercurial'", attr.name),
-                    .nixCode = NixCode { .errPos = *attr.pos }
+                    .errPos = *attr.pos
                 });
         }
 
         if (url.empty())
             throw EvalError({
                 .hint = hintfmt("'url' argument required"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
     } else
diff --git a/src/libexpr/primops/fetchTree.cc b/src/libexpr/primops/fetchTree.cc
index 9be93710a..01d6ad8b0 100644
--- a/src/libexpr/primops/fetchTree.cc
+++ b/src/libexpr/primops/fetchTree.cc
@@ -68,7 +68,7 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
         if (!attrs.count("type"))
             throw Error({
                 .hint = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
 
         input = fetchers::inputFromAttrs(attrs);
@@ -112,14 +112,14 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
             else
                 throw EvalError({
                     .hint = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
-                    .nixCode = NixCode { .errPos = *attr.pos }
+                    .errPos = *attr.pos
                 });
             }
 
         if (!url)
             throw EvalError({
                 .hint = hintfmt("'url' argument required"),
-                .nixCode = NixCode { .errPos = pos }
+                .errPos = pos
             });
     } else
         url = state.forceStringNoCtx(*args[0], pos);
diff --git a/src/libexpr/primops/fromTOML.cc b/src/libexpr/primops/fromTOML.cc
index 7615d1379..b00827a4b 100644
--- a/src/libexpr/primops/fromTOML.cc
+++ b/src/libexpr/primops/fromTOML.cc
@@ -83,7 +83,7 @@ static void prim_fromTOML(EvalState & state, const Pos & pos, Value * * args, Va
     } catch (std::runtime_error & e) {
         throw EvalError({
             .hint = hintfmt("while parsing a TOML string: %s", e.what()),
-            .nixCode = NixCode { .errPos = pos }
+            .errPos = pos
         });
     }
 }
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index a0dfdbdbd..322dfea3b 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -10,45 +10,14 @@ namespace nix {
 
 const std::string nativeSystem = SYSTEM;
 
-// addPrefix is used for show-trace.  Strings added with addPrefix
-// will print ahead of the error itself.
-// BaseError & BaseError::addPrefix(const FormatOrString & fs)
-// {
-//     prefix_ = fs.s + prefix_;
-//     return *this;
-// }
-
-// const string & prefix() const
-// {
-//   // build prefix string on demand??
-
-// }
-// ; //  { return prefix_; }
-
-
-// addPrefix is used for show-trace.  Strings added with addPrefix
-// will print ahead of the error itself.
+// Traces show the chain of calls in nix code.  If an ErrPos is included the surrounding
+// lines of code will print. 
 BaseError & BaseError::addTrace(std::optional<ErrPos> e, hintformat hint)
 {
     err.traces.push_front(Trace { .pos = e, .hint = hint});
     return *this;
 }
 
-// const string& BaseError::calcTrace() const
-// {
-//     if (trace_.has_value())
-//         return *trace_;
-//     else {
-//         err.name = sname();
-
-//         std::ostringstream oss;
-//         oss << err;
-//         trace_ = oss.str();
-
-//         return *trace_;
-//     }
-// }
-
 // c++ std::exception descendants must have a 'const char* what()' function.
 // This stringifies the error and caches it for use by what(), or similarly by msg().
 const string& BaseError::calcWhat() const
@@ -281,23 +250,25 @@ std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo)
             einfo.programName.value_or(""));
 
     bool nl = false;  // intersperse newline between sections.
-    if (einfo.nixCode.has_value()) {
-        switch (einfo.nixCode->errPos.origin) {
+    if (einfo.errPos.has_value()) {
+        switch (einfo.errPos->origin) {
             case foFile: {
                 out << prefix << std::endl;
-                auto &pos = einfo.nixCode->errPos;
-                out << ANSI_BLUE << "at: " << ANSI_YELLOW << showErrPos(pos) << 
-                  ANSI_BLUE << " in file: " << ANSI_NORMAL << pos.file  << std::endl;
+                auto &pos = *einfo.errPos;
+                out << prefix << ANSI_BLUE << "at: " << ANSI_YELLOW << showErrPos(pos) << 
+                  ANSI_BLUE << " in file: " << ANSI_NORMAL << pos.file;
                 break;
             }
             case foString: {
                 out << prefix << std::endl;
-                out << fmt("%1%from command line argument %2%", prefix, showErrPos(einfo.nixCode->errPos)) << std::endl;
+                out << prefix << ANSI_BLUE << "at: " << ANSI_YELLOW << showErrPos(*einfo.errPos) << 
+                  ANSI_BLUE << " from command line argument" << ANSI_NORMAL;
                 break;
             }
             case foStdin: {
                 out << prefix << std::endl;
-                out << fmt("%1%from stdin %2%", prefix, showErrPos(einfo.nixCode->errPos)) << std::endl;
+                out << prefix << ANSI_BLUE << "at: " << ANSI_YELLOW << showErrPos(*einfo.errPos) << 
+                  ANSI_BLUE << " from stdin" << ANSI_NORMAL;
                 break;
             }
             default:
@@ -314,8 +285,8 @@ std::ostream& operator<<(std::ostream &out, const ErrorInfo &einfo)
         nl = true;
     }
 
-    if (einfo.nixCode.has_value()) {
-        NixCode nixcode = *einfo.nixCode;
+    if (einfo.errPos.has_value()) {
+        NixCode nixcode { .errPos = *einfo.errPos }; 
         getCodeLines(nixcode);
 
         // lines of code.
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index 75ba80365..d992c4ece 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -103,7 +103,7 @@ struct ErrorInfo {
     string name;
     string description;
     std::optional<hintformat> hint;
-    std::optional<NixCode> nixCode;
+    std::optional<ErrPos> errPos;
     std::list<Trace> traces;
 
     static std::optional<string> programName;
diff --git a/src/libutil/tests/logging.cc b/src/libutil/tests/logging.cc
index ac4a1b161..0bbec482f 100644
--- a/src/libutil/tests/logging.cc
+++ b/src/libutil/tests/logging.cc
@@ -11,6 +11,13 @@ namespace nix {
      * logEI
      * --------------------------------------------------------------------------*/
 
+    const char *test_file = 
+        "previous line of code\n"
+        "this is the problem line of code\n"
+        "next line of code\n";
+    const char *one_liner = 
+        "this is the problem line of code";
+
     TEST(logEI, catpuresBasicProperties) {
 
         MakeError(TestError, Error);
@@ -152,7 +159,7 @@ namespace nix {
 
     TEST(logError, logErrorWithPreviousAndNextLinesOfCode) {
         SymbolTable testTable;
-        auto problem_file = testTable.create("myfile.nix");
+        auto problem_file = testTable.create(test_file);
 
         testing::internal::CaptureStderr();
 
@@ -162,21 +169,16 @@ namespace nix {
                 .hint = hintfmt("this hint has %1% templated %2%!!",
                     "yellow",
                     "values"),
-                .nixCode = NixCode {
-                    .errPos = Pos(foFile, problem_file, 40, 13),
-                    .prevLineOfCode = "previous line of code",
-                    .errLineOfCode = "this is the problem line of code",
-                    .nextLineOfCode = "next line of code",
-                }});
-
+                .errPos = Pos(foString, problem_file, 02, 13),
+            });
 
         auto str = testing::internal::GetCapturedStderr();
-        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\nin file: \x1B[34;1mmyfile.nix (40:13)\x1B[0m\n\nerror with code lines\n\n    39| previous line of code\n    40| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n    41| next line of code\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
+        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(2:13)\x1B[34;1m from command line argument\x1B[0m\n\nerror with code lines\n\n     1| previous line of code\n     2| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n     3| next line of code\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
     }
 
-    TEST(logError, logErrorWithoutLinesOfCode) {
+    TEST(logError, logErrorWithInvalidFile) {
         SymbolTable testTable;
-        auto problem_file = testTable.create("myfile.nix");
+        auto problem_file = testTable.create("invalid filename");
         testing::internal::CaptureStderr();
 
         logError({
@@ -185,28 +187,23 @@ namespace nix {
                 .hint = hintfmt("this hint has %1% templated %2%!!",
                     "yellow",
                     "values"),
-                .nixCode = NixCode {
-                    .errPos = Pos(foFile, problem_file, 40, 13)
-                }});
+                .errPos = Pos(foFile, problem_file, 02, 13)
+            });
 
         auto str = testing::internal::GetCapturedStderr();
-        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\nin file: \x1B[34;1mmyfile.nix (40:13)\x1B[0m\n\nerror without any code lines.\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
+        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- SysError --- error-unit-test\x1B[0m\nopening file '\x1B[33;1minvalid filename\x1B[0m': \x1B[33;1mNo such file or directory\x1B[0m\n\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(2:13)\x1B[34;1m in file: \x1B[0minvalid filename\n\nerror without any code lines.\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
     }
 
     TEST(logError, logErrorWithOnlyHintAndName) {
-        SymbolTable testTable;
-        auto problem_file = testTable.create("myfile.nix");
         testing::internal::CaptureStderr();
 
         logError({
                 .name = "error name",
                 .hint = hintfmt("hint %1%", "only"),
-                .nixCode = NixCode {
-                    .errPos = Pos(foFile, problem_file, 40, 13)
-                }});
+            });
 
         auto str = testing::internal::GetCapturedStderr();
-        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\nin file: \x1B[34;1mmyfile.nix (40:13)\x1B[0m\n\nhint \x1B[33;1monly\x1B[0m\n");
+        ASSERT_STREQ(str.c_str(), "\x1B[31;1merror:\x1B[0m\x1B[34;1m --- error name --- error-unit-test\x1B[0m\nhint \x1B[33;1monly\x1B[0m\n");
 
     }
 
@@ -219,18 +216,18 @@ namespace nix {
 
         logWarning({
                 .name = "name",
-                .description = "error description",
+                .description = "warning description",
                 .hint = hintfmt("there was a %1%", "warning"),
             });
 
         auto str = testing::internal::GetCapturedStderr();
-        ASSERT_STREQ(str.c_str(), "\x1B[33;1mwarning:\x1B[0m\x1B[34;1m --- name --- error-unit-test\x1B[0m\nerror description\n\nthere was a \x1B[33;1mwarning\x1B[0m\n");
+        ASSERT_STREQ(str.c_str(), "\x1B[33;1mwarning:\x1B[0m\x1B[34;1m --- name --- error-unit-test\x1B[0m\nwarning description\n\nthere was a \x1B[33;1mwarning\x1B[0m\n");
     }
 
     TEST(logWarning, logWarningWithFileLineNumAndCode) {
 
         SymbolTable testTable;
-        auto problem_file = testTable.create("myfile.nix");
+        auto problem_file = testTable.create(test_file);
 
         testing::internal::CaptureStderr();
 
@@ -240,16 +237,12 @@ namespace nix {
                 .hint = hintfmt("this hint has %1% templated %2%!!",
                     "yellow",
                     "values"),
-                .nixCode = NixCode {
-                    .errPos = Pos(foFile, problem_file, 40, 13),
-                    .prevLineOfCode = std::nullopt,
-                    .errLineOfCode = "this is the problem line of code",
-                    .nextLineOfCode = std::nullopt
-                }});
+                .errPos = Pos(foStdin, problem_file, 2, 13),
+            });
 
 
         auto str = testing::internal::GetCapturedStderr();
-        ASSERT_STREQ(str.c_str(), "\x1B[33;1mwarning:\x1B[0m\x1B[34;1m --- warning name --- error-unit-test\x1B[0m\nin file: \x1B[34;1mmyfile.nix (40:13)\x1B[0m\n\nwarning description\n\n    40| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
+        ASSERT_STREQ(str.c_str(), "\x1B[33;1mwarning:\x1B[0m\x1B[34;1m --- warning name --- error-unit-test\x1B[0m\n\x1B[34;1mat: \x1B[33;1m(2:13)\x1B[34;1m from stdin\x1B[0m\n\nwarning description\n\n     1| previous line of code\n     2| this is the problem line of code\n      |             \x1B[31;1m^\x1B[0m\n     3| next line of code\n\nthis hint has \x1B[33;1myellow\x1B[0m templated \x1B[33;1mvalues\x1B[0m!!\n");
     }
 
     /* ----------------------------------------------------------------------------