Merge pull request #9925 from 9999years/fmt-cleanup

Cleanup `fmt.hh`

(cherry picked from commit 47a1dbb4b8e7913cbb9b4d604728b912e76e4ca0)
Change-Id: Id076a45cb39652f437fe3f8bda10c310a9894777

29 files changed, 202 insertions, 151 deletions

diff --git a/src/build-remote/build-remote.cc b/src/build-remote/build-remote.cc
index 519e03242..118468477 100644
--- a/src/build-remote/build-remote.cc
+++ b/src/build-remote/build-remote.cc
@@ -202,7 +202,7 @@ static int main_build_remote(int argc, char * * argv)
                         else
                             drvstr = "<unknown>";
 
-                        auto error = hintformat(errorText);
+                        auto error = HintFmt(errorText);
                         error
                             % drvstr
                             % neededSystem
diff --git a/src/libexpr/eval-error.cc b/src/libexpr/eval-error.cc
index 250c59a19..f4cdeec5c 100644
--- a/src/libexpr/eval-error.cc
+++ b/src/libexpr/eval-error.cc
@@ -28,7 +28,7 @@ template<class T>
 EvalErrorBuilder<T> & EvalErrorBuilder<T>::withTrace(PosIdx pos, const std::string_view text)
 {
     error.err.traces.push_front(
-        Trace{.pos = error.state.positions[pos], .hint = hintfmt(std::string(text)), .frame = false});
+        Trace{.pos = error.state.positions[pos], .hint = HintFmt(std::string(text)), .frame = false});
     return *this;
 }
 
@@ -36,7 +36,7 @@ template<class T>
 EvalErrorBuilder<T> & EvalErrorBuilder<T>::withFrameTrace(PosIdx pos, const std::string_view text)
 {
     error.err.traces.push_front(
-        Trace{.pos = error.state.positions[pos], .hint = hintformat(std::string(text)), .frame = true});
+        Trace{.pos = error.state.positions[pos], .hint = HintFmt(std::string(text)), .frame = true});
     return *this;
 }
 
@@ -57,13 +57,13 @@ EvalErrorBuilder<T> & EvalErrorBuilder<T>::withFrame(const Env & env, const Expr
         .pos = error.state.positions[expr.getPos()],
         .expr = expr,
         .env = env,
-        .hint = hintformat("Fake frame for debugging purposes"),
+        .hint = HintFmt("Fake frame for debugging purposes"),
         .isError = true});
     return *this;
 }
 
 template<class T>
-EvalErrorBuilder<T> & EvalErrorBuilder<T>::addTrace(PosIdx pos, hintformat hint, bool frame)
+EvalErrorBuilder<T> & EvalErrorBuilder<T>::addTrace(PosIdx pos, HintFmt hint, bool frame)
 {
     error.addTrace(error.state.positions[pos], hint, frame);
     return *this;
@@ -75,7 +75,7 @@ EvalErrorBuilder<T> &
 EvalErrorBuilder<T>::addTrace(PosIdx pos, std::string_view formatString, const Args &... formatArgs)
 {
 
-    addTrace(error.state.positions[pos], hintfmt(std::string(formatString), formatArgs...));
+    addTrace(error.state.positions[pos], HintFmt(std::string(formatString), formatArgs...));
     return *this;
 }
 
diff --git a/src/libexpr/eval-error.hh b/src/libexpr/eval-error.hh
index e9076f28b..2bb607280 100644
--- a/src/libexpr/eval-error.hh
+++ b/src/libexpr/eval-error.hh
@@ -90,7 +90,7 @@ public:
 
     [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> & withFrame(const Env & e, const Expr & ex);
 
-    [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> & addTrace(PosIdx pos, hintformat hint, bool frame = false);
+    [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> & addTrace(PosIdx pos, HintFmt hint, bool frame = false);
 
     template<typename... Args>
     [[nodiscard, gnu::noinline]] EvalErrorBuilder<T> &
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index fac67950b..ba9fe9c65 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -809,7 +809,7 @@ void EvalState::addErrorTrace(Error & e, const char * s, const std::string & s2)
 
 void EvalState::addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2, bool frame) const
 {
-    e.addTrace(positions[pos], hintfmt(s, s2), frame);
+    e.addTrace(positions[pos], HintFmt(s, s2), frame);
 }
 
 template<typename... Args>
@@ -825,7 +825,7 @@ static std::unique_ptr<DebugTraceStacker> makeDebugTraceStacker(
             .pos = std::move(pos),
             .expr = expr,
             .env = env,
-            .hint = hintfmt(formatArgs...),
+            .hint = HintFmt(formatArgs...),
             .isError = false
         });
 }
@@ -2782,7 +2782,7 @@ std::optional<std::string> EvalState::resolveSearchPathPath(const SearchPath::Pa
             res = { store->toRealPath(storePath) };
         } catch (FileTransferError & e) {
             logWarning({
-                .msg = hintfmt("Nix search path entry '%1%' cannot be downloaded, ignoring", value)
+                .msg = HintFmt("Nix search path entry '%1%' cannot be downloaded, ignoring", value)
             });
             res = std::nullopt;
         }
@@ -2802,7 +2802,7 @@ std::optional<std::string> EvalState::resolveSearchPathPath(const SearchPath::Pa
             res = { path };
         else {
             logWarning({
-                .msg = hintfmt("Nix search path entry '%1%' does not exist, ignoring", value)
+                .msg = HintFmt("Nix search path entry '%1%' does not exist, ignoring", value)
             });
             res = std::nullopt;
         }
diff --git a/src/libexpr/eval.hh b/src/libexpr/eval.hh
index 325ae792c..135e5fecb 100644
--- a/src/libexpr/eval.hh
+++ b/src/libexpr/eval.hh
@@ -147,7 +147,7 @@ struct DebugTrace {
     std::shared_ptr<Pos> pos;
     const Expr & expr;
     const Env & env;
-    hintformat hint;
+    HintFmt hint;
     bool isError;
 };
 
diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index e45526a6c..305d84a68 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -148,7 +148,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
         } catch (Error & e) {
             e.addTrace(
                 state.positions[attr.pos],
-                hintfmt("while evaluating flake attribute '%s'", state.symbols[attr.name]));
+                HintFmt("while evaluating flake attribute '%s'", state.symbols[attr.name]));
             throw;
         }
     }
@@ -157,7 +157,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
         try {
             input.ref = FlakeRef::fromAttrs(attrs);
         } catch (Error & e) {
-            e.addTrace(state.positions[pos], hintfmt("while evaluating flake input"));
+            e.addTrace(state.positions[pos], HintFmt("while evaluating flake input"));
             throw;
         }
     else {
diff --git a/src/libexpr/lexer.l b/src/libexpr/lexer.l
index fb06c3d69..adb9d9757 100644
--- a/src/libexpr/lexer.l
+++ b/src/libexpr/lexer.l
@@ -153,7 +153,7 @@ or          { return OR_KW; }
                   yylval->n = boost::lexical_cast<int64_t>(yytext);
               } catch (const boost::bad_lexical_cast &) {
                   throw ParseError(ErrorInfo{
-                      .msg = hintfmt("invalid integer '%1%'", yytext),
+                      .msg = HintFmt("invalid integer '%1%'", yytext),
                       .pos = state->positions[CUR_POS],
                   });
               }
@@ -163,7 +163,7 @@ or          { return OR_KW; }
               yylval->nf = strtod(yytext, 0);
               if (errno != 0)
                   throw ParseError(ErrorInfo{
-                      .msg = hintfmt("invalid float '%1%'", yytext),
+                      .msg = HintFmt("invalid float '%1%'", yytext),
                       .pos = state->positions[CUR_POS],
                   });
               return FLOAT;
@@ -292,7 +292,7 @@ or          { return OR_KW; }
 <INPATH_SLASH>{ANY} |
 <INPATH_SLASH><<EOF>> {
   throw ParseError(ErrorInfo{
-      .msg = hintfmt("path has a trailing slash"),
+      .msg = HintFmt("path has a trailing slash"),
       .pos = state->positions[CUR_POS],
   });
 }
diff --git a/src/libexpr/parser-state.hh b/src/libexpr/parser-state.hh
index 2fc072ca4..acadb676d 100644
--- a/src/libexpr/parser-state.hh
+++ b/src/libexpr/parser-state.hh
@@ -63,7 +63,7 @@ struct ParserState
 inline void ParserState::dupAttr(const AttrPath & attrPath, const PosIdx pos, const PosIdx prevPos)
 {
     throw ParseError({
-         .msg = hintfmt("attribute '%1%' already defined at %2%",
+         .msg = HintFmt("attribute '%1%' already defined at %2%",
              showAttrPath(symbols, attrPath), positions[prevPos]),
          .pos = positions[pos]
     });
@@ -72,7 +72,7 @@ inline void ParserState::dupAttr(const AttrPath & attrPath, const PosIdx pos, co
 inline void ParserState::dupAttr(Symbol attr, const PosIdx pos, const PosIdx prevPos)
 {
     throw ParseError({
-        .msg = hintfmt("attribute '%1%' already defined at %2%", symbols[attr], positions[prevPos]),
+        .msg = HintFmt("attribute '%1%' already defined at %2%", symbols[attr], positions[prevPos]),
         .pos = positions[pos]
     });
 }
@@ -153,13 +153,13 @@ inline Formals * ParserState::validateFormals(Formals * formals, PosIdx pos, Sym
     }
     if (duplicate)
         throw ParseError({
-            .msg = hintfmt("duplicate formal function argument '%1%'", symbols[duplicate->first]),
+            .msg = HintFmt("duplicate formal function argument '%1%'", symbols[duplicate->first]),
             .pos = positions[duplicate->second]
         });
 
     if (arg && formals->has(arg))
         throw ParseError({
-            .msg = hintfmt("duplicate formal function argument '%1%'", symbols[arg]),
+            .msg = HintFmt("duplicate formal function argument '%1%'", symbols[arg]),
             .pos = positions[pos]
         });
 
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index fc83ee2dd..447e4d61a 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -63,7 +63,7 @@ using namespace nix;
 void yyerror(YYLTYPE * loc, yyscan_t scanner, ParserState * state, const char * error)
 {
     throw ParseError({
-        .msg = hintfmt(error),
+        .msg = HintFmt(error),
         .pos = state->positions[state->at(*loc)]
     });
 }
@@ -152,7 +152,7 @@ expr_function
   | LET binds IN expr_function
     { if (!$2->dynamicAttrs.empty())
         throw ParseError({
-            .msg = hintfmt("dynamic attributes not allowed in let"),
+            .msg = HintFmt("dynamic attributes not allowed in let"),
             .pos = state->positions[CUR_POS]
         });
       $$ = new ExprLet($2, $4);
@@ -242,7 +242,7 @@ expr_simple
       static bool noURLLiterals = experimentalFeatureSettings.isEnabled(Xp::NoUrlLiterals);
       if (noURLLiterals)
           throw ParseError({
-              .msg = hintfmt("URL literals are disabled"),
+              .msg = HintFmt("URL literals are disabled"),
               .pos = state->positions[CUR_POS]
           });
       $$ = new ExprString(std::string($1));
@@ -338,7 +338,7 @@ attrs
           delete str;
       } else
           throw ParseError({
-              .msg = hintfmt("dynamic attributes not allowed in inherit"),
+              .msg = HintFmt("dynamic attributes not allowed in inherit"),
               .pos = state->positions[state->at(@2)]
           });
     }
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 8e06d55a1..86db527f6 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -748,7 +748,7 @@ static RegisterPrimOp primop_break({
         if (state.debugRepl && !state.debugTraces.empty()) {
             auto error = Error(ErrorInfo {
                 .level = lvlInfo,
-                .msg = hintfmt("breakpoint reached"),
+                .msg = HintFmt("breakpoint reached"),
                 .pos = state.positions[pos],
             });
 
@@ -759,7 +759,7 @@ static RegisterPrimOp primop_break({
                 // If the user elects to quit the repl, throw an exception.
                 throw Error(ErrorInfo{
                     .level = lvlInfo,
-                    .msg = hintfmt("quit the debugger"),
+                    .msg = HintFmt("quit the debugger"),
                     .pos = nullptr,
                 });
             }
@@ -814,7 +814,7 @@ static void prim_addErrorContext(EvalState & state, const PosIdx pos, Value * *
         auto message = state.coerceToString(pos, *args[0], context,
                 "while evaluating the error message passed to builtins.addErrorContext",
                 false, false).toOwned();
-        e.addTrace(nullptr, hintfmt(message), true);
+        e.addTrace(nullptr, HintFmt(message), true);
         throw;
     }
 }
@@ -1065,7 +1065,7 @@ static void prim_derivationStrict(EvalState & state, const PosIdx pos, Value * *
          * often results from the composition of several functions
          * (derivationStrict, derivation, mkDerivation, mkPythonModule, etc.)
          */
-        e.addTrace(nullptr, hintfmt(
+        e.addTrace(nullptr, HintFmt(
                 "while evaluating derivation '%s'\n"
                 "  whose name attribute is located at %s",
                 drvName, pos), true);
@@ -1226,7 +1226,7 @@ drvName, Bindings * attrs, Value & v)
 
         } catch (Error & e) {
             e.addTrace(state.positions[i->pos],
-                hintfmt("while evaluating attribute '%1%' of derivation '%2%'", key, drvName),
+                HintFmt("while evaluating attribute '%1%' of derivation '%2%'", key, drvName),
                 true);
             throw;
         }
diff --git a/src/libexpr/primops/fetchClosure.cc b/src/libexpr/primops/fetchClosure.cc
index ca2a3df9c..3804db6eb 100644
--- a/src/libexpr/primops/fetchClosure.cc
+++ b/src/libexpr/primops/fetchClosure.cc
@@ -22,7 +22,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
         auto rewrittenPath = makeContentAddressed(fromStore, *state.store, fromPath);
         if (toPathMaybe && *toPathMaybe != rewrittenPath)
             throw Error({
-                .msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected",
+                .msg = HintFmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected",
                     state.store->printStorePath(fromPath),
                     state.store->printStorePath(rewrittenPath),
                     state.store->printStorePath(*toPathMaybe)),
@@ -30,7 +30,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
             });
         if (!toPathMaybe)
             throw Error({
-                .msg = hintfmt(
+                .msg = HintFmt(
                     "rewriting '%s' to content-addressed form yielded '%s'\n"
                     "Use this value for the 'toPath' attribute passed to 'fetchClosure'",
                     state.store->printStorePath(fromPath),
@@ -49,7 +49,7 @@ static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Stor
         // We don't perform the rewriting when outPath already exists, as an optimisation.
         // However, we can quickly detect a mistake if the toPath is input addressed.
         throw Error({
-            .msg = hintfmt(
+            .msg = HintFmt(
                 "The 'toPath' value '%s' is input-addressed, so it can't possibly be the result of rewriting to a content-addressed path.\n\n"
                 "Set 'toPath' to an empty string to make Nix report the correct content-addressed path.",
                 state.store->printStorePath(toPath)),
@@ -72,7 +72,7 @@ static void runFetchClosureWithContentAddressedPath(EvalState & state, const Pos
 
     if (!info->isContentAddressed(*state.store)) {
         throw Error({
-            .msg = hintfmt(
+            .msg = HintFmt(
                 "The 'fromPath' value '%s' is input-addressed, but 'inputAddressed' is set to 'false' (default).\n\n"
                 "If you do intend to fetch an input-addressed store path, add\n\n"
                 "    inputAddressed = true;\n\n"
@@ -98,7 +98,7 @@ static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosId
 
     if (info->isContentAddressed(*state.store)) {
         throw Error({
-            .msg = hintfmt(
+            .msg = HintFmt(
                 "The store object referred to by 'fromPath' at '%s' is not input-addressed, but 'inputAddressed' is set to 'true'.\n\n"
                 "Remove the 'inputAddressed' attribute (it defaults to 'false') to expect 'fromPath' to be content-addressed",
                 state.store->printStorePath(fromPath)),
@@ -152,14 +152,14 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
 
         else
             throw Error({
-                .msg = hintfmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
+                .msg = HintFmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
                 .pos = state.positions[pos]
             });
     }
 
     if (!fromPath)
         throw Error({
-            .msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
+            .msg = HintFmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
             .pos = state.positions[pos]
         });
 
@@ -168,7 +168,7 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
     if (inputAddressed) {
         if (toPath)
             throw Error({
-                .msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
+                .msg = HintFmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
                     "inputAddressed",
                     "toPath"),
                 .pos = state.positions[pos]
@@ -177,7 +177,7 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
 
     if (!fromStoreUrl)
         throw Error({
-            .msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
+            .msg = HintFmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
             .pos = state.positions[pos]
         });
 
@@ -187,13 +187,13 @@ static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * arg
         parsedURL.scheme != "https" &&
         !(getEnv("_NIX_IN_TEST").has_value() && parsedURL.scheme == "file"))
         throw Error({
-            .msg = hintfmt("'fetchClosure' only supports http:// and https:// stores"),
+            .msg = HintFmt("'fetchClosure' only supports http:// and https:// stores"),
             .pos = state.positions[pos]
         });
 
     if (!parsedURL.query.empty())
         throw Error({
-            .msg = hintfmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
+            .msg = HintFmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
             .pos = state.positions[pos]
         });
 
diff --git a/src/libexpr/print.cc b/src/libexpr/print.cc
index 86eadfb17..b792f657d 100644
--- a/src/libexpr/print.cc
+++ b/src/libexpr/print.cc
@@ -510,7 +510,7 @@ std::ostream & operator<<(std::ostream & output, const ValuePrinter & printer)
 }
 
 template<>
-hintformat & hintformat::operator%(const ValuePrinter & value)
+HintFmt & HintFmt::operator%(const ValuePrinter & value)
 {
         fmt % value;
         return *this;
diff --git a/src/libexpr/print.hh b/src/libexpr/print.hh
index a542bc7b1..7ddda81b8 100644
--- a/src/libexpr/print.hh
+++ b/src/libexpr/print.hh
@@ -86,6 +86,6 @@ std::ostream & operator<<(std::ostream & output, const ValuePrinter & printer);
  * magenta.
  */
 template<>
-hintformat & hintformat::operator%(const ValuePrinter & value);
+HintFmt & HintFmt::operator%(const ValuePrinter & value);
 
 }
diff --git a/src/libexpr/value-to-json.cc b/src/libexpr/value-to-json.cc
index ab479520b..787a46426 100644
--- a/src/libexpr/value-to-json.cc
+++ b/src/libexpr/value-to-json.cc
@@ -64,7 +64,7 @@ json printValueAsJSON(EvalState & state, bool strict,
                         out[j] = printValueAsJSON(state, strict, *a.value, a.pos, context, copyToStore);
                     } catch (Error & e) {
                         e.addTrace(state.positions[a.pos],
-                            hintfmt("while evaluating attribute '%1%'", j));
+                            HintFmt("while evaluating attribute '%1%'", j));
                         throw;
                     }
                 }
@@ -81,7 +81,7 @@ json printValueAsJSON(EvalState & state, bool strict,
                     out.push_back(printValueAsJSON(state, strict, *elem, pos, context, copyToStore));
                 } catch (Error & e) {
                     e.addTrace(state.positions[pos],
-                        hintfmt("while evaluating list element at index %1%", i));
+                        HintFmt("while evaluating list element at index %1%", i));
                     throw;
                 }
                 i++;
diff --git a/src/libexpr/value/context.hh b/src/libexpr/value/context.hh
index 9f1d59317..998b70e36 100644
--- a/src/libexpr/value/context.hh
+++ b/src/libexpr/value/context.hh
@@ -20,8 +20,8 @@ public:
         : Error("")
     {
         raw = raw_;
-        auto hf = hintfmt(args...);
-        err.msg = hintfmt("Bad String Context element: %1%: %2%", normaltxt(hf.str()), raw);
+        auto hf = HintFmt(args...);
+        err.msg = HintFmt("Bad String Context element: %1%: %2%", Uncolored(hf.str()), raw);
     }
 };
 
diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index dadaccbcf..5de6d8d79 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -708,7 +708,7 @@ void DerivationGoal::tryToBuild()
     if (!outputLocks.lockPaths(lockFiles, "", false)) {
         if (!actLock)
             actLock = std::make_unique<Activity>(*logger, lvlWarn, actBuildWaiting,
-                fmt("waiting for lock on %s", magentatxt(showPaths(lockFiles))));
+                fmt("waiting for lock on %s", Magenta(showPaths(lockFiles))));
         worker.waitForAWhile(shared_from_this());
         return;
     }
@@ -762,7 +762,7 @@ void DerivationGoal::tryToBuild()
                    the wake-up timeout expires. */
                 if (!actLock)
                     actLock = std::make_unique<Activity>(*logger, lvlWarn, actBuildWaiting,
-                        fmt("waiting for a machine to build '%s'", magentatxt(worker.store.printStorePath(drvPath))));
+                        fmt("waiting for a machine to build '%s'", Magenta(worker.store.printStorePath(drvPath))));
                 worker.waitForAWhile(shared_from_this());
                 outputLocks.unlock();
                 return;
@@ -987,7 +987,7 @@ void DerivationGoal::buildDone()
             diskFull |= cleanupDecideWhetherDiskFull();
 
             auto msg = fmt("builder for '%s' %s",
-                magentatxt(worker.store.printStorePath(drvPath)),
+                Magenta(worker.store.printStorePath(drvPath)),
                 statusToString(status));
 
             if (!logger->isVerbose() && !logTail.empty()) {
@@ -1523,7 +1523,7 @@ void DerivationGoal::done(
     outputLocks.unlock();
     buildResult.status = status;
     if (ex)
-        buildResult.errorMsg = fmt("%s", normaltxt(ex->info().msg));
+        buildResult.errorMsg = fmt("%s", Uncolored(ex->info().msg));
     if (buildResult.status == BuildResult::TimedOut)
         worker.timedOut = true;
     if (buildResult.status == BuildResult::PermanentFailure)
diff --git a/src/libstore/build/local-derivation-goal.cc b/src/libstore/build/local-derivation-goal.cc
index 8e5ab7594..c4fae0eaa 100644
--- a/src/libstore/build/local-derivation-goal.cc
+++ b/src/libstore/build/local-derivation-goal.cc
@@ -87,7 +87,7 @@ void handleDiffHook(
         } catch (Error & error) {
             ErrorInfo ei = error.info();
             // FIXME: wrap errors.
-            ei.msg = hintfmt("diff hook execution failed: %s", ei.msg.str());
+            ei.msg = HintFmt("diff hook execution failed: %s", ei.msg.str());
             logError(ei);
         }
     }
@@ -227,7 +227,7 @@ void LocalDerivationGoal::tryLocalBuild()
         if (!buildUser) {
             if (!actLock)
                 actLock = std::make_unique<Activity>(*logger, lvlWarn, actBuildWaiting,
-                    fmt("waiting for a free build user ID for '%s'", magentatxt(worker.store.printStorePath(drvPath))));
+                    fmt("waiting for a free build user ID for '%s'", Magenta(worker.store.printStorePath(drvPath))));
             worker.waitForAWhile(shared_from_this());
             return;
         }
diff --git a/src/libstore/filetransfer.cc b/src/libstore/filetransfer.cc
index a283af5a2..0d09fff98 100644
--- a/src/libstore/filetransfer.cc
+++ b/src/libstore/filetransfer.cc
@@ -881,12 +881,12 @@ template<typename... Args>
 FileTransferError::FileTransferError(FileTransfer::Error error, std::optional<std::string> response, const Args & ... args)
     : Error(args...), error(error), response(response)
 {
-    const auto hf = hintfmt(args...);
+    const auto hf = HintFmt(args...);
     // FIXME: Due to https://github.com/NixOS/nix/issues/3841 we don't know how
     // to print different messages for different verbosity levels. For now
     // we add some heuristics for detecting when we want to show the response.
     if (response && (response->size() < 1024 || response->find("<html>") != std::string::npos))
-        err.msg = hintfmt("%1%\n\nresponse body:\n\n%2%", normaltxt(hf.str()), chomp(*response));
+        err.msg = HintFmt("%1%\n\nresponse body:\n\n%2%", Uncolored(hf.str()), chomp(*response));
     else
         err.msg = hf;
 }
diff --git a/src/libstore/sqlite.cc b/src/libstore/sqlite.cc
index 7c8decb74..365794bd3 100644
--- a/src/libstore/sqlite.cc
+++ b/src/libstore/sqlite.cc
@@ -9,19 +9,19 @@
 
 namespace nix {
 
-SQLiteError::SQLiteError(const char *path, const char *errMsg, int errNo, int extendedErrNo, int offset, hintformat && hf)
+SQLiteError::SQLiteError(const char *path, const char *errMsg, int errNo, int extendedErrNo, int offset, HintFmt && hf)
   : Error(""), path(path), errMsg(errMsg), errNo(errNo), extendedErrNo(extendedErrNo), offset(offset)
 {
     auto offsetStr = (offset == -1) ? "" : "at offset " + std::to_string(offset) + ": ";
-    err.msg = hintfmt("%s: %s%s, %s (in '%s')",
-        normaltxt(hf.str()),
+    err.msg = HintFmt("%s: %s%s, %s (in '%s')",
+        Uncolored(hf.str()),
         offsetStr,
         sqlite3_errstr(extendedErrNo),
         errMsg,
         path ? path : "(in-memory)");
 }
 
-[[noreturn]] void SQLiteError::throw_(sqlite3 * db, hintformat && hf)
+[[noreturn]] void SQLiteError::throw_(sqlite3 * db, HintFmt && hf)
 {
     int err = sqlite3_errcode(db);
     int exterr = sqlite3_extended_errcode(db);
@@ -32,7 +32,7 @@ SQLiteError::SQLiteError(const char *path, const char *errMsg, int errNo, int ex
 
     if (err == SQLITE_BUSY || err == SQLITE_PROTOCOL) {
         auto exp = SQLiteBusy(path, errMsg, err, exterr, offset, std::move(hf));
-        exp.err.msg = hintfmt(
+        exp.err.msg = HintFmt(
             err == SQLITE_PROTOCOL
                 ? "SQLite database '%s' is busy (SQLITE_PROTOCOL)"
                 : "SQLite database '%s' is busy",
@@ -248,7 +248,7 @@ void handleSQLiteBusy(const SQLiteBusy & e, time_t & nextWarning)
     if (now > nextWarning) {
         nextWarning = now + 10;
         logWarning({
-            .msg = hintfmt(e.what())
+            .msg = HintFmt(e.what())
         });
     }
 
diff --git a/src/libstore/sqlite.hh b/src/libstore/sqlite.hh
index 0c08267f7..003e4d101 100644
--- a/src/libstore/sqlite.hh
+++ b/src/libstore/sqlite.hh
@@ -142,19 +142,19 @@ struct SQLiteError : Error
 
     template<typename... Args>
     [[noreturn]] static void throw_(sqlite3 * db, const std::string & fs, const Args & ... args) {
-        throw_(db, hintfmt(fs, args...));
+        throw_(db, HintFmt(fs, args...));
     }
 
-    SQLiteError(const char *path, const char *errMsg, int errNo, int extendedErrNo, int offset, hintformat && hf);
+    SQLiteError(const char *path, const char *errMsg, int errNo, int extendedErrNo, int offset, HintFmt && hf);
 
 protected:
 
     template<typename... Args>
     SQLiteError(const char *path, const char *errMsg, int errNo, int extendedErrNo, int offset, const std::string & fs, const Args & ... args)
-      : SQLiteError(path, errNo, extendedErrNo, offset, hintfmt(fs, args...))
+      : SQLiteError(path, errMsg, errNo, extendedErrNo, offset, HintFmt(fs, args...))
     { }
 
-    [[noreturn]] static void throw_(sqlite3 * db, hintformat && hf);
+    [[noreturn]] static void throw_(sqlite3 * db, HintFmt && hf);
 
 };
 
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 649caed86..49a18fa1c 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -10,7 +10,7 @@ namespace nix {
 
 const std::string nativeSystem = SYSTEM;
 
-void BaseError::addTrace(std::shared_ptr<Pos> && e, hintformat hint, bool frame)
+void BaseError::addTrace(std::shared_ptr<Pos> && e, HintFmt hint, bool frame)
 {
     err.traces.push_front(Trace { .pos = std::move(e), .hint = hint, .frame = frame });
 }
@@ -36,7 +36,7 @@ const std::string & BaseError::calcWhat() const
 
 std::optional<std::string> ErrorInfo::programName = std::nullopt;
 
-std::ostream & operator <<(std::ostream & os, const hintformat & hf)
+std::ostream & operator <<(std::ostream & os, const HintFmt & hf)
 {
     return os << hf.str();
 }
diff --git a/src/libutil/error.hh b/src/libutil/error.hh
index d67b26e0f..0d978803e 100644
--- a/src/libutil/error.hh
+++ b/src/libutil/error.hh
@@ -63,7 +63,7 @@ void printCodeLines(std::ostream & out,
 
 struct Trace {
     std::shared_ptr<Pos> pos;
-    hintformat hint;
+    HintFmt hint;
     bool frame;
 };
 
@@ -74,7 +74,7 @@ inline bool operator>=(const Trace& lhs, const Trace& rhs);
 
 struct ErrorInfo {
     Verbosity level;
-    hintformat msg;
+    HintFmt msg;
     std::shared_ptr<Pos> pos;
     std::list<Trace> traces;
 
@@ -113,20 +113,20 @@ public:
 
     template<typename... Args>
     BaseError(unsigned int status, const Args & ... args)
-        : err { .level = lvlError, .msg = hintfmt(args...), .status = status }
+        : err { .level = lvlError, .msg = HintFmt(args...), .status = status }
     { }
 
     template<typename... Args>
     explicit BaseError(const std::string & fs, const Args & ... args)
-        : err { .level = lvlError, .msg = hintfmt(fs, args...) }
+        : err { .level = lvlError, .msg = HintFmt(fs, args...) }
     { }
 
     template<typename... Args>
     BaseError(const Suggestions & sug, const Args & ... args)
-        : err { .level = lvlError, .msg = hintfmt(args...), .suggestions = sug }
+        : err { .level = lvlError, .msg = HintFmt(args...), .suggestions = sug }
     { }
 
-    BaseError(hintformat hint)
+    BaseError(HintFmt hint)
         : err { .level = lvlError, .msg = hint }
     { }
 
@@ -159,10 +159,10 @@ public:
     template<typename... Args>
     void addTrace(std::shared_ptr<Pos> && e, std::string_view fs, const Args & ... args)
     {
-        addTrace(std::move(e), hintfmt(std::string(fs), args...));
+        addTrace(std::move(e), HintFmt(std::string(fs), args...));
     }
 
-    void addTrace(std::shared_ptr<Pos> && e, hintformat hint, bool frame = false);
+    void addTrace(std::shared_ptr<Pos> && e, HintFmt hint, bool frame = false);
 
     bool hasTrace() const { return !err.traces.empty(); }
 
@@ -190,8 +190,8 @@ public:
         : Error("")
     {
         errNo = errNo_;
-        auto hf = hintfmt(args...);
-        err.msg = hintfmt("%1%: %2%", normaltxt(hf.str()), strerror(errNo));
+        auto hf = HintFmt(args...);
+        err.msg = HintFmt("%1%: %2%", Uncolored(hf.str()), strerror(errNo));
     }
 
     template<typename... Args>
diff --git a/src/libutil/fmt.hh b/src/libutil/fmt.hh
index f552a6b77..75354a07c 100644
--- a/src/libutil/fmt.hh
+++ b/src/libutil/fmt.hh
@@ -8,37 +8,64 @@
 
 namespace nix {
 
-
-/**
- * Inherit some names from other namespaces for convenience.
- */
-using boost::format;
-
-
-/**
- * A variadic template that does nothing. Useful to call a function
- * for all variadic arguments but ignoring the result.
- */
-struct nop { template<typename... T> nop(T...) {} };
-
-
+namespace {
 /**
- * A helper for formatting strings. ‘fmt(format, a_0, ..., a_n)’ is
- * equivalent to ‘boost::format(format) % a_0 % ... %
- * ... a_n’. However, ‘fmt(s)’ is equivalent to ‘s’ (so no %-expansion
- * takes place).
+ * A helper for writing `boost::format` expressions.
+ *
+ * These are equivalent:
+ *
+ * ```
+ * formatHelper(formatter, a_0, ..., a_n)
+ * formatter % a_0 % ... % a_n
+ * ```
+ *
+ * With a single argument, `formatHelper(s)` is a no-op.
  */
 template<class F>
 inline void formatHelper(F & f)
-{
-}
+{ }
 
 template<class F, typename T, typename... Args>
 inline void formatHelper(F & f, const T & x, const Args & ... args)
 {
+    // Interpolate one argument and then recurse.
     formatHelper(f % x, args...);
 }
 
+/**
+ * Set the correct exceptions for `fmt`.
+ */
+void setExceptions(boost::format & fmt)
+{
+    fmt.exceptions(
+        boost::io::all_error_bits ^
+        boost::io::too_many_args_bit ^
+        boost::io::too_few_args_bit);
+}
+}
+
+/**
+ * A helper for writing a `boost::format` expression to a string.
+ *
+ * These are (roughly) equivalent:
+ *
+ * ```
+ * fmt(formatString, a_0, ..., a_n)
+ * (boost::format(formatString) % a_0 % ... % a_n).str()
+ * ```
+ *
+ * However, when called with a single argument, the string is returned
+ * unchanged.
+ *
+ * If you write code like this:
+ *
+ * ```
+ * std::cout << boost::format(stringFromUserInput) << std::endl;
+ * ```
+ *
+ * And `stringFromUserInput` contains formatting placeholders like `%s`, then
+ * the code will crash at runtime. `fmt` helps you avoid this pitfall.
+ */
 inline std::string fmt(const std::string & s)
 {
     return s;
@@ -53,66 +80,96 @@ template<typename... Args>
 inline std::string fmt(const std::string & fs, const Args & ... args)
 {
     boost::format f(fs);
-    f.exceptions(boost::io::all_error_bits ^ boost::io::too_many_args_bit);
+    setExceptions(f);
     formatHelper(f, args...);
     return f.str();
 }
 
-// format function for hints in errors.  same as fmt, except templated values
-// are always in magenta.
+/**
+ * Values wrapped in this struct are printed in magenta.
+ *
+ * By default, arguments to `HintFmt` are printed in magenta. To avoid this,
+ * either wrap the argument in `Uncolored` or add a specialization of
+ * `HintFmt::operator%`.
+ */
 template <class T>
-struct magentatxt
+struct Magenta
 {
-    magentatxt(const T &s) : value(s) {}
+    Magenta(const T &s) : value(s) {}
     const T & value;
 };
 
 template <class T>
-std::ostream & operator<<(std::ostream & out, const magentatxt<T> & y)
+std::ostream & operator<<(std::ostream & out, const Magenta<T> & y)
 {
     return out << ANSI_WARNING << y.value << ANSI_NORMAL;
 }
 
+/**
+ * Values wrapped in this class are printed without coloring.
+ *
+ * By default, arguments to `HintFmt` are printed in magenta (see `Magenta`).
+ */
 template <class T>
-struct normaltxt
+struct Uncolored
 {
-    normaltxt(const T & s) : value(s) {}
+    Uncolored(const T & s) : value(s) {}
     const T & value;
 };
 
 template <class T>
-std::ostream & operator<<(std::ostream & out, const normaltxt<T> & y)
+std::ostream & operator<<(std::ostream & out, const Uncolored<T> & y)
 {
     return out << ANSI_NORMAL << y.value;
 }
 
-class hintformat
+/**
+ * A wrapper around `boost::format` which colors interpolated arguments in
+ * magenta by default.
+ */
+class HintFmt
 {
+private:
+    boost::format fmt;
+
 public:
-    hintformat(const std::string & format) : fmt(format)
-    {
-        fmt.exceptions(boost::io::all_error_bits ^
-                       boost::io::too_many_args_bit ^
-                       boost::io::too_few_args_bit);
-    }
+    /**
+     * Format the given string literally, without interpolating format
+     * placeholders.
+     */
+    HintFmt(const std::string & literal)
+        : HintFmt("%s", Uncolored(literal))
+    { }
+
+    /**
+     * Interpolate the given arguments into the format string.
+     */
+    template<typename... Args>
+    HintFmt(const std::string & format, const Args & ... args)
+        : HintFmt(boost::format(format), args...)
+    { }
 
-    hintformat(const hintformat & hf)
+    HintFmt(const HintFmt & hf)
         : fmt(hf.fmt)
     { }
 
-    hintformat(format && fmt)
+    template<typename... Args>
+    HintFmt(boost::format && fmt, const Args & ... args)
         : fmt(std::move(fmt))
-    { }
+    {
+        setExceptions(fmt);
+        formatHelper(*this, args...);
+    }
 
     template<class T>
-    hintformat & operator%(const T & value)
+    HintFmt & operator%(const T & value)
     {
-        fmt % magentatxt(value);
+        fmt % Magenta(value);
         return *this;
     }
 
     template<class T>
-    hintformat & operator%(const normaltxt<T> & value)
+    HintFmt & operator%(const Uncolored<T> & value)
     {
         fmt % value.value;
         return *this;
@@ -122,25 +179,8 @@ public:
     {
         return fmt.str();
     }
-
-private:
-    format fmt;
 };
 
-std::ostream & operator<<(std::ostream & os, const hintformat & hf);
-
-template<typename... Args>
-inline hintformat hintfmt(const std::string & fs, const Args & ... args)
-{
-    hintformat f(fs);
-    formatHelper(f, args...);
-    return f;
-}
-
-inline hintformat hintfmt(const std::string & plain_string)
-{
-    // we won't be receiving any args in this case, so just print the original string
-    return hintfmt("%s", normaltxt(plain_string));
-}
+std::ostream & operator<<(std::ostream & os, const HintFmt & hf);
 
 }
diff --git a/src/libutil/logging.hh b/src/libutil/logging.hh
index 5aa6bee95..7a6341d70 100644
--- a/src/libutil/logging.hh
+++ b/src/libutil/logging.hh
@@ -118,6 +118,17 @@ public:
     { }
 };
 
+/**
+ * A variadic template that does nothing.
+ *
+ * Useful to call a function with each argument in a parameter pack.
+ */
+struct nop
+{
+    template<typename... T> nop(T...)
+    { }
+};
+
 ActivityId getCurActivity();
 void setCurActivity(const ActivityId activityId);
 
diff --git a/src/libutil/serialise.cc b/src/libutil/serialise.cc
index 6b0d87b03..3d9dcf728 100644
--- a/src/libutil/serialise.cc
+++ b/src/libutil/serialise.cc
@@ -444,7 +444,7 @@ Error readError(Source & source)
     auto msg = readString(source);
     ErrorInfo info {
         .level = level,
-        .msg = hintfmt(msg),
+        .msg = HintFmt(msg),
     };
     auto havePos = readNum<size_t>(source);
     assert(havePos == 0);
@@ -453,7 +453,7 @@ Error readError(Source & source)
         havePos = readNum<size_t>(source);
         assert(havePos == 0);
         info.traces.push_back(Trace {
-            .hint = hintfmt(readString(source))
+            .hint = HintFmt(readString(source))
         });
     }
     return Error(std::move(info));
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index ef2654a14..007ec8bef 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1872,7 +1872,7 @@ void setStackSize(rlim_t stackSize)
         if (setrlimit(RLIMIT_STACK, &limit) != 0) {
             logger->log(
                 lvlError,
-                hintfmt(
+                HintFmt(
                     "Failed to increase stack size from %1% to %2% (maximum allowed stack size: %3%): %4%",
                     savedStackSize,
                     stackSize,
diff --git a/src/nix/daemon.cc b/src/nix/daemon.cc
index af428018a..f2eea2cf4 100644
--- a/src/nix/daemon.cc
+++ b/src/nix/daemon.cc
@@ -376,7 +376,7 @@ static void daemonLoop(std::optional<TrustedFlag> forceTrustClientOpt)
         } catch (Error & error) {
             auto ei = error.info();
             // FIXME: add to trace?
-            ei.msg = hintfmt("error processing connection: %1%", ei.msg.str());
+            ei.msg = HintFmt("error processing connection: %1%", ei.msg.str());
             logError(ei);
         }
     }
diff --git a/src/nix/eval.cc b/src/nix/eval.cc
index 9ec861a89..2698a6de8 100644
--- a/src/nix/eval.cc
+++ b/src/nix/eval.cc
@@ -98,7 +98,7 @@ struct CmdEval : MixJSON, InstallableValueCommand, MixReadOnlyOption
                         } catch (Error & e) {
                             e.addTrace(
                                 state->positions[attr.pos],
-                                hintfmt("while evaluating the attribute '%s'", name));
+                                HintFmt("while evaluating the attribute '%s'", name));
                             throw;
                         }
                     }
diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index a11e39534..bbefff87a 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -370,7 +370,7 @@ struct CmdFlakeCheck : FlakeCommand
                     return storePath;
                 }
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the derivation '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the derivation '%s'", attrPath));
                 reportError(e);
             }
             return std::nullopt;
@@ -389,7 +389,7 @@ struct CmdFlakeCheck : FlakeCommand
                 }
                 #endif
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the app definition '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the app definition '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -413,7 +413,7 @@ struct CmdFlakeCheck : FlakeCommand
                 // FIXME: if we have a 'nixpkgs' input, use it to
                 // evaluate the overlay.
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the overlay '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the overlay '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -424,7 +424,7 @@ struct CmdFlakeCheck : FlakeCommand
                     fmt("checking NixOS module '%s'", attrPath));
                 state->forceValue(v, pos);
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the NixOS module '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the NixOS module '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -452,7 +452,7 @@ struct CmdFlakeCheck : FlakeCommand
                 }
 
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the Hydra jobset '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the Hydra jobset '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -467,7 +467,7 @@ struct CmdFlakeCheck : FlakeCommand
                 if (!state->isDerivation(*vToplevel))
                     throw Error("attribute 'config.system.build.toplevel' is not a derivation");
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the NixOS configuration '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the NixOS configuration '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -501,7 +501,7 @@ struct CmdFlakeCheck : FlakeCommand
                         throw Error("template '%s' has unsupported attribute '%s'", attrPath, name);
                 }
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the template '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the template '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -515,7 +515,7 @@ struct CmdFlakeCheck : FlakeCommand
                     throw Error("bundler must be a function");
                 // TODO: check types of inputs/outputs?
             } catch (Error & e) {
-                e.addTrace(resolve(pos), hintfmt("while checking the template '%s'", attrPath));
+                e.addTrace(resolve(pos), HintFmt("while checking the template '%s'", attrPath));
                 reportError(e);
             }
         };
@@ -735,7 +735,7 @@ struct CmdFlakeCheck : FlakeCommand
                             warn("unknown flake output '%s'", name);
 
                     } catch (Error & e) {
-                        e.addTrace(resolve(pos), hintfmt("while checking flake output '%s'", name));
+                        e.addTrace(resolve(pos), HintFmt("while checking flake output '%s'", name));
                         reportError(e);
                     }
                 });