[clang-tools-extra] [clang-tidy] Preserve comments in `readability-use-std-min-max` (PR #169908)

[via cfe-commits]

https://github.com/zeyi2 created https://github.com/llvm/llvm-project/pull/169908

Closes [#121613](https://github.com/llvm/llvm-project/issues/121613)

>From 3b7d92ba5fb8d5849e68369fc0f8ea56d1cf494d Mon Sep 17 00:00:00 2001
From: mtx <mitchell.xu2 at gmail.com>
Date: Fri, 28 Nov 2025 20:06:44 +0800
Subject: [PATCH] [clang-tidy] Preserve comments in
 `readability-use-std-min-max`

---
 .../readability/UseStdMinMaxCheck.cpp         | 23 ++++++++++++-------
 clang-tools-extra/docs/ReleaseNotes.rst       |  5 ++++
 .../checkers/readability/use-std-min-max.cpp  | 11 +++++++++
 3 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp b/clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp
index 5a7add88d6eeb..f78e62fbc3c27 100644
--- a/clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/UseStdMinMaxCheck.cpp
@@ -96,12 +96,11 @@ static QualType getReplacementCastType(const Expr *CondLhs, const Expr *CondRhs,
   return GlobalImplicitCastType;
 }
 
-static std::string createReplacement(const Expr *CondLhs, const Expr *CondRhs,
-                                     const Expr *AssignLhs,
-                                     const SourceManager &Source,
-                                     const LangOptions &LO,
-                                     StringRef FunctionName,
-                                     const BinaryOperator *BO) {
+static std::string
+createReplacement(const Expr *CondLhs, const Expr *CondRhs,
+                  const Expr *AssignLhs, const SourceManager &Source,
+                  const LangOptions &LO, StringRef FunctionName,
+                  const BinaryOperator *BO, StringRef Comment = "") {
   const llvm::StringRef CondLhsStr = Lexer::getSourceText(
       Source.getExpansionRange(CondLhs->getSourceRange()), Source, LO);
   const llvm::StringRef CondRhsStr = Lexer::getSourceText(
@@ -116,7 +115,7 @@ static std::string createReplacement(const Expr *CondLhs, const Expr *CondRhs,
           (!GlobalImplicitCastType.isNull()
                ? "<" + GlobalImplicitCastType.getAsString() + ">("
                : "(") +
-          CondLhsStr + ", " + CondRhsStr + ");")
+          CondLhsStr + ", " + CondRhsStr + ");" + Comment)
       .str();
 }
 
@@ -172,13 +171,21 @@ void UseStdMinMaxCheck::check(const MatchFinder::MatchResult &Result) {
 
   auto ReplaceAndDiagnose = [&](const llvm::StringRef FunctionName) {
     const SourceManager &Source = *Result.SourceManager;
+    const std::string Comment =
+        Lexer::getSourceText(
+            CharSourceRange::getCharRange(
+                Lexer::getLocForEndOfToken(If->getRParenLoc(), 0, Source, LO),
+                If->getThen()->getBeginLoc()),
+            Source, LO)
+            .rtrim()
+            .str();
     diag(IfLocation, "use `%0` instead of `%1`")
         << FunctionName << BinaryOp->getOpcodeStr()
         << FixItHint::CreateReplacement(
                SourceRange(IfLocation, Lexer::getLocForEndOfToken(
                                            ThenLocation, 0, Source, LO)),
                createReplacement(CondLhs, CondRhs, AssignLhs, Source, LO,
-                                 FunctionName, BinaryOp))
+                                 FunctionName, BinaryOp, Comment))
         << IncludeInserter.createIncludeInsertion(
                Source.getFileID(If->getBeginLoc()), AlgorithmHeader);
   };
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index a6f80e3721db1..d2da19b61132c 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -555,6 +555,11 @@ Changes in existing checks
   <clang-tidy/checks/readability/use-concise-preprocessor-directives>` check to
   generate correct fix-its for forms without a space after the directive.
 
+- Improved :doc:`readability-use-std-min-max
+  <clang-tidy/checks/readability/use-std-min-max>` check by ensuring that
+  comments between the ``if`` condition and the ``then`` block are preserved
+  when applying the fix.
+
 Removed checks
 ^^^^^^^^^^^^^^
 
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/use-std-min-max.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/use-std-min-max.cpp
index 35ade8a7c6d37..f51bf1ae98ed1 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/use-std-min-max.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/use-std-min-max.cpp
@@ -273,3 +273,14 @@ void useRight() {
 }
 
 } // namespace gh121676
+
+void testComment() {
+  int box_depth = 10;
+  int max_depth = 5;
+  // CHECK-MESSAGES: :[[@LINE+2]]:3: warning: use `std::min` instead of `>` [readability-use-std-min-max]
+  // CHECK-FIXES: box_depth = std::min(box_depth, max_depth); // limit the depth to max
+  if (box_depth > max_depth) // limit the depth to max
+  {
+    box_depth = max_depth;
+  }
+}