[clang-tools-extra] [clang-tidy] Fix false positive in `readability-redundant-typename` (PR #170034)

[via cfe-commits]

https://github.com/zeyi2 created https://github.com/llvm/llvm-project/pull/170034

Closes #169166

>From e8bc35d273950cc6d5f1e947db1d34741de52432 Mon Sep 17 00:00:00 2001
From: mtx <mitchell.xu2 at gmail.com>
Date: Sun, 30 Nov 2025 20:54:12 +0800
Subject: [PATCH] [clang-tidy] Fix false positive in
 readability-redundant-typename

---
 .../readability/RedundantTypenameCheck.cpp         |  6 ++++--
 clang-tools-extra/docs/ReleaseNotes.rst            |  4 ++++
 .../checkers/readability/redundant-typename.cpp    | 14 ++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
index a4edd2b46b86b..feb09086f3cfd 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantTypenameCheck.cpp
@@ -47,8 +47,10 @@ void RedundantTypenameCheck::check(const MatchFinder::MatchResult &Result) {
   const SourceLocation ElaboratedKeywordLoc = [&] {
     if (const auto *NonDependentTypeLoc =
             Result.Nodes.getNodeAs<TypeLoc>("nonDependentTypeLoc")) {
-      if (const auto TL = NonDependentTypeLoc->getAs<TypedefTypeLoc>())
-        return TL.getElaboratedKeywordLoc();
+      if (const auto TL = NonDependentTypeLoc->getAs<TypedefTypeLoc>()) {
+        if (!TL.getType()->isDependentType())
+          return TL.getElaboratedKeywordLoc();
+      }
 
       if (const auto TL = NonDependentTypeLoc->getAs<TagTypeLoc>())
         return TL.getElaboratedKeywordLoc();
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index a6f80e3721db1..19c5db0ac08be 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -547,6 +547,10 @@ Changes in existing checks
   <clang-tidy/checks/readability/qualified-auto>` check by adding the option
   `IgnoreAliasing`, that allows not looking at underlying types of type aliases.
 
+- Improved :doc:`readability-redundant-typename
+  <clang-tidy/checks/readability/redundant-typename>` check to correctly
+  handle dependent types in type aliases.
+
 - Improved :doc:`readability-uppercase-literal-suffix
   <clang-tidy/checks/readability/uppercase-literal-suffix>` check to recognize
   literal suffixes added in C++23 and C23.
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-typename.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-typename.cpp
index 2efafd1a9a649..35e239bf5694d 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-typename.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-typename.cpp
@@ -267,3 +267,17 @@ WHOLE_TYPE_IN_MACRO Macro2;
 
 #define WHOLE_DECLARATION_IN_MACRO typename NotDependent::R Macro3
 WHOLE_DECLARATION_IN_MACRO;
+
+template<typename T> struct ListWrapper {};
+template<typename T>
+class ClassWrapper {
+public:
+    using Argument = ListWrapper<T>;
+    ListWrapper<Argument> arguments;
+    ListWrapper<Argument> getArguments() const;
+};
+template<typename T>
+ListWrapper<typename ClassWrapper<T>::Argument> ClassWrapper<T>::getArguments() const {
+    return arguments;
+}
+// CHECK-NOT: warning: redundant 'typename' [readability-redundant-typename]