Revert extra colon at end os strings

src/libcmd/installables.cc

@@ -524,7 +524,7 @@ ref<eval_cache::EvalCache> openEvalCache(
             auto vFlake = state.allocValue();
             flake::callFlake(state, *lockedFlake, *vFlake);
 
-            state.forceAttrs(*vFlake, noPos, "While evaluating a cached flake: ");
+            state.forceAttrs(*vFlake, noPos, "While evaluating a cached flake");
 
             auto aOutputs = vFlake->attrs->get(state.symbols.create("outputs"));
             assert(aOutputs);

src/libexpr/attr-path.cc

@@ -112,7 +112,7 @@ Pos findPackageFilename(EvalState & state, Value & v, std::string what)
 
     // FIXME: is it possible to extract the Pos object instead of doing this
     //        toString + parsing?
-    auto pos = state.forceString(*v2, noPos, "While evaluating the meta.position attribute of a derivation: ");
+    auto pos = state.forceString(*v2, noPos, "While evaluating the meta.position attribute of a derivation");
 
     auto colon = pos.rfind(':');
     if (colon == std::string::npos)

src/libexpr/eval-cache.cc

@@ -336,7 +336,7 @@ Value & AttrCursor::getValue()
     if (!_value) {
         if (parent) {
             auto & vParent = parent->first->getValue();
-            root->state.forceAttrs(vParent, noPos, "While evaluating the parent attr set: ");
+            root->state.forceAttrs(vParent, noPos, "While evaluating the parent attr set");
             auto attr = vParent.attrs->get(parent->second);
             if (!attr)
                 throw Error("attribute '%s' is unexpectedly missing", getAttrPathStr());

src/libexpr/eval.cc

@@ -297,7 +297,7 @@ static Symbol getName(const AttrName & name, EvalState & state, Env & env)
     } else {
         Value nameValue;
         name.expr->eval(state, env, nameValue);
-        state.forceStringNoCtx(nameValue, noPos, "While evaluating an attribute name: ");
+        state.forceStringNoCtx(nameValue, noPos, "While evaluating an attribute name");
         return state.symbols.create(nameValue.string.s);
     }
 }
@@ -1111,7 +1111,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
            Hence we need __overrides.) */
         if (hasOverrides) {
             Value * vOverrides = (*v.attrs)[overrides->second.displ].value;
-            state.forceAttrs(*vOverrides, [&]() { return vOverrides->determinePos(noPos); }, "While evaluating the `__overrides` attribute: ");
+            state.forceAttrs(*vOverrides, [&]() { return vOverrides->determinePos(noPos); }, "While evaluating the `__overrides` attribute");
             Bindings * newBnds = state.allocBindings(v.attrs->capacity() + vOverrides->attrs->size());
             for (auto & i : *v.attrs)
                 newBnds->push_back(i);
@@ -1139,7 +1139,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
         state.forceValue(nameVal, i.pos);
         if (nameVal.type() == nNull)
             continue;
-        state.forceStringNoCtx(nameVal, i.pos, "While evaluating the name of a dynamic attribute: ");
+        state.forceStringNoCtx(nameVal, i.pos, "While evaluating the name of a dynamic attribute");
         Symbol nameSym = state.symbols.create(nameVal.string.s);
         Bindings::iterator j = v.attrs->find(nameSym);
         if (j != v.attrs->end())
@@ -1229,7 +1229,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
                     return;
                 }
             } else {
-                state.forceAttrs(*vAttrs, pos, "While selecting an attribute: ");
+                state.forceAttrs(*vAttrs, pos, "While selecting an attribute");
                 if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
                     throwEvalError(pos, "attribute '%1%' missing", name);
             }

src/libexpr/flake/flake.cc

@@ -708,7 +708,7 @@ static void prim_getFlake(EvalState & state, const Pos & pos, Value * * args, Va
 {
     state.requireExperimentalFeatureOnEvaluation(Xp::Flakes, "builtins.getFlake", pos);
 
-    std::string flakeRefS(state.forceStringNoCtx(*args[0], pos, "While evaluating the argument passed to builtins.getFlake: "));
+    std::string flakeRefS(state.forceStringNoCtx(*args[0], pos, "While evaluating the argument passed to builtins.getFlake"));
     auto flakeRef = parseFlakeRef(flakeRefS, {}, true);
     if (evalSettings.pureEval && !flakeRef.input.isLocked())
         throw Error("cannot call 'getFlake' on unlocked flake reference '%s', at %s (use --impure to override)", flakeRefS, pos);

src/libexpr/get-drvs.cc

@@ -50,7 +50,7 @@ std::string DrvInfo::queryName() const
     if (name == "" && attrs) {
         auto i = attrs->find(state->sName);
         if (i == attrs->end()) throw TypeError("derivation name missing");
-        name = state->forceStringNoCtx(*i->value, noPos, "While evaluating the name of a DrvInfo: ");
+        name = state->forceStringNoCtx(*i->value, noPos, "While evaluating the name of a DrvInfo");
     }
     return name;
 }
@@ -60,7 +60,7 @@ std::string DrvInfo::querySystem() const
 {
     if (system == "" && attrs) {
         auto i = attrs->find(state->sSystem);
-        system = i == attrs->end() ? "unknown" : state->forceStringNoCtx(*i->value, *i->pos, "While evaluating the system of a DrvInfo: ");
+        system = i == attrs->end() ? "unknown" : state->forceStringNoCtx(*i->value, *i->pos, "While evaluating the system of a DrvInfo");
     }
     return system;
 }
@@ -74,7 +74,7 @@ std::optional<StorePath> DrvInfo::queryDrvPath() const
         if (i == attrs->end())
             drvPath = {std::nullopt};
         else
-            drvPath = {state->coerceToStorePath(*i->pos, *i->value, context, "Whyle evaluating the drv path of a DrvInfo: ")};
+            drvPath = {state->coerceToStorePath(*i->pos, *i->value, context, "Whyle evaluating the drv path of a DrvInfo")};
     }
     return drvPath.value_or(std::nullopt);
 }
@@ -94,7 +94,7 @@ StorePath DrvInfo::queryOutPath() const
         Bindings::iterator i = attrs->find(state->sOutPath);
         PathSet context;
         if (i != attrs->end())
-            outPath = state->coerceToStorePath(*i->pos, *i->value, context, "While evaluating the output path of a DrvInfo: ");
+            outPath = state->coerceToStorePath(*i->pos, *i->value, context, "While evaluating the output path of a DrvInfo");
     }
     if (!outPath)
         throw UnimplementedError("CA derivations are not yet supported");
@@ -108,21 +108,21 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool onlyOutputsToInstall)
         /* Get the ‘outputs’ list. */
         Bindings::iterator i;
         if (attrs && (i = attrs->find(state->sOutputs)) != attrs->end()) {
-            state->forceList(*i->value, *i->pos, "While evaluating the outputs of a DrvInfo: ");
+            state->forceList(*i->value, *i->pos, "While evaluating the outputs of a DrvInfo");
 
             /* For each output... */
             for (auto elem : i->value->listItems()) {
                 /* Evaluate the corresponding set. */
-                std::string name(state->forceStringNoCtx(*elem, *i->pos, "While evaluating the name of one output of a DrvInfo: "));
+                std::string name(state->forceStringNoCtx(*elem, *i->pos, "While evaluating the name of one output of a DrvInfo"));
                 Bindings::iterator out = attrs->find(state->symbols.create(name));
                 if (out == attrs->end()) continue; // FIXME: throw error?
-                state->forceAttrs(*out->value, *i->pos, "While evaluating the description of a DrvInfo output: ");
+                state->forceAttrs(*out->value, *i->pos, "While evaluating the description of a DrvInfo output");
 
                 /* And evaluate its ‘outPath’ attribute. */
                 Bindings::iterator outPath = out->value->attrs->find(state->sOutPath);
                 if (outPath == out->value->attrs->end()) continue; // FIXME: throw error?
                 PathSet context;
-                outputs.emplace(name, state->coerceToStorePath(*outPath->pos, *outPath->value, context, "While evaluating the outPath of an output path of a DrvInfo: "));
+                outputs.emplace(name, state->coerceToStorePath(*outPath->pos, *outPath->value, context, "While evaluating the outPath of an output path of a DrvInfo"));
             }
         } else
             outputs.emplace("out", queryOutPath());
@@ -151,7 +151,7 @@ std::string DrvInfo::queryOutputName() const
 {
     if (outputName == "" && attrs) {
         Bindings::iterator i = attrs->find(state->sOutputName);
-        outputName = i != attrs->end() ? state->forceStringNoCtx(*i->value, noPos, "While evaluating the output name of a DrvInfo: ") : "";
+        outputName = i != attrs->end() ? state->forceStringNoCtx(*i->value, noPos, "While evaluating the output name of a DrvInfo") : "";
     }
     return outputName;
 }
@@ -163,7 +163,7 @@ Bindings * DrvInfo::getMeta()
     if (!attrs) return 0;
     Bindings::iterator a = attrs->find(state->sMeta);
     if (a == attrs->end()) return 0;
-    state->forceAttrs(*a->value, *a->pos, "While evaluating the `meta` attribute of a DrvInfo: ");
+    state->forceAttrs(*a->value, *a->pos, "While evaluating the `meta` attribute of a DrvInfo");
     meta = a->value->attrs;
     return meta;
 }
@@ -364,7 +364,7 @@ static void getDerivations(EvalState & state, Value & vIn,
                    `recurseForDerivations = true' attribute. */
                 if (i->value->type() == nAttrs) {
                     Bindings::iterator j = i->value->attrs->find(state.sRecurseForDerivations);
-                    if (j != i->value->attrs->end() && state.forceBool(*j->value, *j->pos, "While evaluating the attribute `recurseForDerivations`: "))
+                    if (j != i->value->attrs->end() && state.forceBool(*j->value, *j->pos, "While evaluating the attribute `recurseForDerivations`"))
                         getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
                 }
             }

src/libexpr/primops.cc

@@ -2805,7 +2805,7 @@ static RegisterPrimOp primop_foldlStrict({
 
 static void anyOrAll(bool any, EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    state.forceFunction(*args[0], pos, std::string("While evaluating the first argument passed to builtins.") + (any ? "any" : "all: "));
+    state.forceFunction(*args[0], pos, std::string("While evaluating the first argument passed to builtins.") + (any ? "any" : "all"));
     state.forceList(*args[1], pos, std::string("While evaluating the second argument passed to builtins.") + (any ? "any" : "all"));
 
     Value vTmp;

src/libexpr/primops/context.cc

@@ -7,7 +7,7 @@ namespace nix {
 static void prim_unsafeDiscardStringContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    auto s = state.coerceToString(pos, *args[0], context, "While evaluating the argument passed to builtins.unsafeDiscardStringContext: ");
+    auto s = state.coerceToString(pos, *args[0], context, "While evaluating the argument passed to builtins.unsafeDiscardStringContext");
     v.mkString(*s);
 }
 
@@ -17,7 +17,7 @@ static RegisterPrimOp primop_unsafeDiscardStringContext("__unsafeDiscardStringCo
 static void prim_hasContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.hasContext: ");
+    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.hasContext");
     v.mkBool(!context.empty());
 }
 
@@ -33,7 +33,7 @@ static RegisterPrimOp primop_hasContext("__hasContext", 1, prim_hasContext);
 static void prim_unsafeDiscardOutputDependency(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    auto s = state.coerceToString(pos, *args[0], context, "While evaluating the argument passed to builtins.unsafeDiscardOutputDependency: ");
+    auto s = state.coerceToString(pos, *args[0], context, "While evaluating the argument passed to builtins.unsafeDiscardOutputDependency");
 
     PathSet context2;
     for (auto & p : context)
@@ -72,7 +72,7 @@ static void prim_getContext(EvalState & state, const Pos & pos, Value * * args,
         Strings outputs;
     };
     PathSet context;
-    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.getContext: ");
+    state.forceString(*args[0], context, pos, "While evaluating the argument passed to builtins.getContext");
     auto contextInfos = std::map<Path, ContextInfo>();
     for (const auto & p : context) {
         Path drv;
@@ -136,9 +136,9 @@ static RegisterPrimOp primop_getContext("__getContext", 1, prim_getContext);
 static void prim_appendContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    auto orig = state.forceString(*args[0], context, pos, "while evaluating the first argument passed to builtins.appendContext: ");
+    auto orig = state.forceString(*args[0], context, pos, "while evaluating the first argument passed to builtins.appendContext");
 
-    state.forceAttrs(*args[1], pos, "While evaluating the second argument passed to builtins.appendContext: ");
+    state.forceAttrs(*args[1], pos, "While evaluating the second argument passed to builtins.appendContext");
 
     auto sPath = state.symbols.create("path");
     auto sAllOutputs = state.symbols.create("allOutputs");
@@ -150,16 +150,16 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
             });
         if (!settings.readOnlyMode)
             state.store->ensurePath(state.store->parseStorePath(i.name));
-        state.forceAttrs(*i.value, *i.pos, "While evaluating the value of a string context: ");
+        state.forceAttrs(*i.value, *i.pos, "While evaluating the value of a string context");
         auto iter = i.value->attrs->find(sPath);
         if (iter != i.value->attrs->end()) {
-            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `path` attribute of a string context: "))
+            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `path` attribute of a string context"))
                 context.insert(i.name);
         }
 
         iter = i.value->attrs->find(sAllOutputs);
         if (iter != i.value->attrs->end()) {
-            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `allOutputs` attribute of a string context: ")) {
+            if (state.forceBool(*iter->value, *iter->pos, "While evaluating the `allOutputs` attribute of a string context")) {
                 if (!isDerivation(i.name)) {
                     throw EvalError({
                         .msg = hintfmt("Tried to add all-outputs context of %s, which is not a derivation, to a string", i.name),
@@ -172,7 +172,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
 
         iter = i.value->attrs->find(state.sOutputs);
         if (iter != i.value->attrs->end()) {
-            state.forceList(*iter->value, *iter->pos, "While evaluating the `outputs` attribute of a string context: ");
+            state.forceList(*iter->value, *iter->pos, "While evaluating the `outputs` attribute of a string context");
             if (iter->value->listSize() && !isDerivation(i.name)) {
                 throw EvalError({
                     .msg = hintfmt("Tried to add derivation output context of %s, which is not a derivation, to a string", i.name),
@@ -180,7 +180,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
                 });
             }
             for (auto elem : iter->value->listItems()) {
-                auto name = state.forceStringNoCtx(*elem, *iter->pos, "While evaluating an output name within a string context: ");
+                auto name = state.forceStringNoCtx(*elem, *iter->pos, "While evaluating an output name within a string context");
                 context.insert(concatStrings("!", name, "!", i.name));
             }
         }

src/libexpr/primops/fetchMercurial.cc

@@ -22,18 +22,18 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
         for (auto & attr : *args[0]->attrs) {
             std::string_view n(attr.name);
             if (n == "url")
-                url = state.coerceToString(*attr.pos, *attr.value, context, false, false, "While evaluating the `url` attribute passed to builtins.fetchMercurial: ").toOwned();
+                url = state.coerceToString(*attr.pos, *attr.value, context, false, false, "While evaluating the `url` attribute passed to builtins.fetchMercurial").toOwned();
             else if (n == "rev") {
                 // Ugly: unlike fetchGit, here the "rev" attribute can
                 // be both a revision or a branch/tag name.
-                auto value = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `rev` attribute passed to builtins.fetchMercurial: ");
+                auto value = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `rev` attribute passed to builtins.fetchMercurial");
                 if (std::regex_match(value.begin(), value.end(), revRegex))
                     rev = Hash::parseAny(value, htSHA1);
                 else
                     ref = value;
             }
             else if (n == "name")
-                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `name` attribute passed to builtins.fetchMercurial: ");
+                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the `name` attribute passed to builtins.fetchMercurial");
             else
                 throw EvalError({
                     .msg = hintfmt("unsupported argument '%s' to 'fetchMercurial'", attr.name),
@@ -48,7 +48,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
             });
 
     } else
-        url = state.coerceToString(pos, *args[0], context, false, false, "While evaluating the first argument passed to builtins.fetchMercurial: ").toOwned();
+        url = state.coerceToString(pos, *args[0], context, false, false, "While evaluating the first argument passed to builtins.fetchMercurial").toOwned();
 
     // FIXME: git externals probably can be used to bypass the URI
     // whitelist. Ah well.

src/libexpr/primops/fetchTree.cc

@@ -102,7 +102,7 @@ static void fetchTree(
     state.forceValue(*args[0], pos);
 
     if (args[0]->type() == nAttrs) {
-        state.forceAttrs(*args[0], pos, "While evaluating the argument passed to builtins.fetchTree: ");
+        state.forceAttrs(*args[0], pos, "While evaluating the argument passed to builtins.fetchTree");
 
         fetchers::Attrs attrs;
 
@@ -112,7 +112,7 @@ static void fetchTree(
                     .msg = hintfmt("unexpected attribute 'type'"),
                     .errPos = pos
                 });
-            type = state.forceStringNoCtx(*aType->value, *aType->pos, "While evaluating the `type` attribute passed to builtins.fetchTree: ");
+            type = state.forceStringNoCtx(*aType->value, *aType->pos, "While evaluating the `type` attribute passed to builtins.fetchTree");
         } else if (!type)
             throw Error({
                 .msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
@@ -151,7 +151,7 @@ static void fetchTree(
 
         input = fetchers::Input::fromAttrs(std::move(attrs));
     } else {
-        auto url = state.coerceToString(pos, *args[0], context, false, false, "While evaluating the first argument passed to the fetcher: ").toOwned();
+        auto url = state.coerceToString(pos, *args[0], context, false, false, "While evaluating the first argument passed to the fetcher").toOwned();
 
         if (type == "git") {
             fetchers::Attrs attrs;
@@ -198,11 +198,11 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
         for (auto & attr : *args[0]->attrs) {
             std::string n(attr.name);
             if (n == "url")
-                url = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the url we should fetch: ");
+                url = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the url we should fetch");
             else if (n == "sha256")
-                expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the sha256 of the content we should fetch: "), htSHA256);
+                expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the sha256 of the content we should fetch"), htSHA256);
             else if (n == "name")
-                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the name of the content we should fetch: ");
+                name = state.forceStringNoCtx(*attr.value, *attr.pos, "While evaluating the name of the content we should fetch");
             else
                 throw EvalError({
                     .msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
@@ -216,7 +216,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
                 .errPos = pos
             });
     } else
-        url = state.forceStringNoCtx(*args[0], pos, "While evaluating the url we should fetch: ");
+        url = state.forceStringNoCtx(*args[0], pos, "While evaluating the url we should fetch");
 
     url = resolveUri(*url);
 

src/libexpr/primops/fromTOML.cc

@@ -7,7 +7,7 @@ namespace nix {
 
 static void prim_fromTOML(EvalState & state, const Pos & pos, Value * * args, Value & val)
 {
-    auto toml = state.forceStringNoCtx(*args[0], pos, "While evaluating the argument passed to builtins.fromTOML: ");
+    auto toml = state.forceStringNoCtx(*args[0], pos, "While evaluating the argument passed to builtins.fromTOML");
 
     std::istringstream tomlStream(std::string{toml});
 

src/nix/eval.cc

@@ -107,7 +107,7 @@ struct CmdEval : MixJSON, InstallableCommand
 
         else if (raw) {
             stopProgressBar();
-            std::cout << *state->coerceToString(noPos, *v, context, "While generating the eval command output: ");
+            std::cout << *state->coerceToString(noPos, *v, context, "While generating the eval command output");
         }
 
         else if (json) {

src/nix/flake.cc

@@ -126,12 +126,12 @@ static void enumerateOutputs(EvalState & state, Value & vFlake,
     std::function<void(const std::string & name, Value & vProvide, const Pos & pos)> callback)
 {
     auto pos = vFlake.determinePos(noPos);
-    state.forceAttrs(vFlake, pos, "While evaluating a flake to get its outputs: ");
+    state.forceAttrs(vFlake, pos, "While evaluating a flake to get its outputs");
 
     auto aOutputs = vFlake.attrs->get(state.symbols.create("outputs"));
     assert(aOutputs);
 
-    state.forceAttrs(*aOutputs->value, pos, "While evaluating the outputs of a flake: ");
+    state.forceAttrs(*aOutputs->value, pos, "While evaluating the outputs of a flake");
 
     auto sHydraJobs = state.symbols.create("hydraJobs");
 

src/nix/main.cc

@@ -196,7 +196,7 @@ static void showHelp(std::vector<std::string> subcommand, MultiCommand & topleve
     if (!attr)
         throw UsageError("Nix has no subcommand '%s'", concatStringsSep("", subcommand));
 
-    auto markdown = state.forceString(*attr->value, noPos, "While evaluating the lowdown help text: ");
+    auto markdown = state.forceString(*attr->value, noPos, "While evaluating the lowdown help text");
 
     RunPager pager;
     std::cout << renderMarkdownToTerminal(markdown) << "\n";

src/nix/prefetch.cc

@@ -28,17 +28,17 @@ std::string resolveMirrorUrl(EvalState & state, const std::string & url)
     Value vMirrors;
     // FIXME: use nixpkgs flake
     state.eval(state.parseExprFromString("import <nixpkgs/pkgs/build-support/fetchurl/mirrors.nix>", "."), vMirrors);
-    state.forceAttrs(vMirrors, noPos, "While evaluating the set of all mirrors: ");
+    state.forceAttrs(vMirrors, noPos, "While evaluating the set of all mirrors");
 
     auto mirrorList = vMirrors.attrs->find(state.symbols.create(mirrorName));
     if (mirrorList == vMirrors.attrs->end())
         throw Error("unknown mirror name '%s'", mirrorName);
-    state.forceList(*mirrorList->value, noPos, "While evaluating this mirror configuration: ");
+    state.forceList(*mirrorList->value, noPos, "While evaluating this mirror configuration");
 
     if (mirrorList->value->listSize() < 1)
         throw Error("mirror URL '%s' did not expand to anything", url);
 
-    std::string mirror(state.forceString(*mirrorList->value->listElems()[0], noPos, "While evaluating the first available mirror: "));
+    std::string mirror(state.forceString(*mirrorList->value->listElems()[0], noPos, "While evaluating the first available mirror"));
     return mirror + (hasSuffix(mirror, "/") ? "" : "/") + s.substr(p + 1);
 }
 
@@ -196,27 +196,27 @@ static int main_nix_prefetch_url(int argc, char * * argv)
             Value vRoot;
             state->evalFile(path, vRoot);
             Value & v(*findAlongAttrPath(*state, attrPath, autoArgs, vRoot).first);
-            state->forceAttrs(v, noPos, "While evaluating the source attribute to prefetch: ");
+            state->forceAttrs(v, noPos, "While evaluating the source attribute to prefetch");
 
             /* Extract the URL. */
             auto & attr = v.attrs->need(state->symbols.create("urls"));
-            state->forceList(*attr.value, noPos, "While evaluating the urls to prefetch: ");
+            state->forceList(*attr.value, noPos, "While evaluating the urls to prefetch");
             if (attr.value->listSize() < 1)
                 throw Error("'urls' list is empty");
-            url = state->forceString(*attr.value->listElems()[0], noPos, "While evaluating the first url from the urls list: ");
+            url = state->forceString(*attr.value->listElems()[0], noPos, "While evaluating the first url from the urls list");
 
             /* Extract the hash mode. */
             auto attr2 = v.attrs->get(state->symbols.create("outputHashMode"));
             if (!attr2)
                 printInfo("warning: this does not look like a fetchurl call");
             else
-                unpack = state->forceString(*attr2->value, noPos, "While evaluating the outputHashMode of the source to prefetch: ") == "recursive";
+                unpack = state->forceString(*attr2->value, noPos, "While evaluating the outputHashMode of the source to prefetch") == "recursive";
 
             /* Extract the name. */
             if (!name) {
                 auto attr3 = v.attrs->get(state->symbols.create("name"));
                 if (!attr3)
-                    name = state->forceString(*attr3->value, noPos, "While evaluating the name of the source to prefetch: ");
+                    name = state->forceString(*attr3->value, noPos, "While evaluating the name of the source to prefetch");
             }
         }
 

src/nix/repl.cc

@@ -342,7 +342,7 @@ StringSet NixRepl::completePrefix(const std::string & prefix)
             Expr * e = parseString(expr);
             Value v;
             e->eval(*state, *env, v);
-            state->forceAttrs(v, noPos, "nevermind, it is ignored anyway: ");
+            state->forceAttrs(v, noPos, "nevermind, it is ignored anyway");
 
             for (auto & i : *v.attrs) {
                 std::string name = i.name;
@@ -461,7 +461,7 @@ bool NixRepl::processLine(std::string line)
 
         if (v.type() == nPath || v.type() == nString) {
             PathSet context;
-            auto filename = state->coerceToString(noPos, v, context, "While evaluating the filename to edit: ");
+            auto filename = state->coerceToString(noPos, v, context, "While evaluating the filename to edit");
             pos.file = state->symbols.create(*filename);
         } else if (v.isLambda()) {
             pos = v.lambda.fun->pos;
@@ -675,7 +675,7 @@ void NixRepl::reloadFiles()
 
 void NixRepl::addAttrsToScope(Value & attrs)
 {
-    state->forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); }, "While evaluating an attribute set to be merged in the global scope: ");
+    state->forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); }, "While evaluating an attribute set to be merged in the global scope");
     if (displ + attrs.attrs->size() >= envSize)
         throw Error("environment full; cannot add more variables");
 
@@ -780,7 +780,7 @@ std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int m
             Bindings::iterator i = v.attrs->find(state->sDrvPath);
             PathSet context;
             if (i != v.attrs->end())
-                str << state->store->printStorePath(state->coerceToStorePath(*i->pos, *i->value, context, "While evaluating the drvPath of a derivation: "));
+                str << state->store->printStorePath(state->coerceToStorePath(*i->pos, *i->value, context, "While evaluating the drvPath of a derivation"));
             else
                 str << "???";
             str << "»";

src/nix/upgrade-nix.cc

@@ -144,7 +144,7 @@ struct CmdUpgradeNix : MixDryRun, StoreCommand
         Bindings & bindings(*state->allocBindings(0));
         auto v2 = findAlongAttrPath(*state, settings.thisSystem, bindings, *v).first;
 
-        return store->parseStorePath(state->forceString(*v2, noPos, "While evaluating the path tho latest nix version: "));
+        return store->parseStorePath(state->forceString(*v2, noPos, "While evaluating the path tho latest nix version"));
     }
 };