[clang-tools-extra] d458f34 - [clang-tidy] Fix `bugprone-incorrect-enable-if` inserting duplicate `typename` (#190899)

[via cfe-commits]

Author: Victor Chernyakin
Date: 2026-04-10T01:22:51Z
New Revision: d458f34b6dbab9e5ad6ba8a34791e80eeaf5c3b1

URL: https://github.com/llvm/llvm-project/commit/d458f34b6dbab9e5ad6ba8a34791e80eeaf5c3b1
DIFF: https://github.com/llvm/llvm-project/commit/d458f34b6dbab9e5ad6ba8a34791e80eeaf5c3b1.diff

LOG:  [clang-tidy] Fix `bugprone-incorrect-enable-if` inserting duplicate `typename` (#190899)

This PR resolves one of our FIXME's. Pre-C++20, this check turns
```cpp
typename std::enable_if<...>
```
into
```cpp
typename typename std::enable_if<...>::type
```
instead of 
```cpp
typename std::enable_if<...>::type
```

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/bugprone/incorrect-enable-if.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
index 6181ac84f36e3..5a592e10a599e 100644
--- a/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
+++ b/clang-tools-extra/clang-tidy/bugprone/IncorrectEnableIfCheck.cpp
@@ -47,8 +47,8 @@ void IncorrectEnableIfCheck::check(const MatchFinder::MatchResult &Result) {
       Result.Nodes.getNodeAs<TemplateSpecializationTypeLoc>(
           "enable_if_specialization");
 
-  if (!EnableIf || !EnableIfSpecializationLoc)
-    return;
+  assert(EnableIf);
+  assert(EnableIfSpecializationLoc);
 
   const SourceManager &SM = *Result.SourceManager;
   const SourceLocation RAngleLoc =
@@ -57,9 +57,8 @@ void IncorrectEnableIfCheck::check(const MatchFinder::MatchResult &Result) {
   auto Diag = diag(EnableIf->getBeginLoc(),
                    "incorrect std::enable_if usage detected; use "
                    "'typename std::enable_if<...>::type'");
-  // FIXME: This should handle the enable_if specialization already having an
-  // elaborated keyword.
-  if (!getLangOpts().CPlusPlus20) {
+  if (!getLangOpts().CPlusPlus20 &&
+      EnableIfSpecializationLoc->getElaboratedKeywordLoc().isInvalid()) {
     Diag << FixItHint::CreateInsertion(EnableIfSpecializationLoc->getBeginLoc(),
                                        "typename ");
   }

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index caf0275035064..7b47643a47c75 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -252,6 +252,12 @@ Changes in existing checks
   positive when increment/decrement operators appear inside lambda bodies that
   are part of a condition expression.
 
+- Improved :doc:`bugprone-incorrect-enable-if
+  <clang-tidy/checks/bugprone/incorrect-enable-if>` check to not
+  insert an extraneous ``typename`` on code like
+  ``typename std::enable_if<...>``, where there's already a ``typename`` and
+  only the ``::type`` at the end is missing.
+
 - Improved :doc:`bugprone-macro-parentheses
   <clang-tidy/checks/bugprone/macro-parentheses>` check by printing the macro
   definition in the warning message if the macro is defined on command line.

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/incorrect-enable-if.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/incorrect-enable-if.cpp
index 0c418efe1420b..81612a50e5bbd 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/bugprone/incorrect-enable-if.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/incorrect-enable-if.cpp
@@ -42,6 +42,12 @@ void invalid_multiple() {}
 // CHECK-FIXES: template <typename T, typename = typename std::enable_if<T::some_value>::type, typename = typename std::enable_if<T::other_value>::type>
 // CHECK-FIXES-CXX20: template <typename T, typename = std::enable_if<T::some_value>::type, typename = std::enable_if<T::other_value>::type>
 
+template <typename T, typename = typename std::enable_if<T::some_value>>
+void invalid_typename_keyword() {}
+// CHECK-MESSAGES: [[@LINE-2]]:23: warning: incorrect std::enable_if usage detected; use 'typename std::enable_if<...>::type' [bugprone-incorrect-enable-if]
+// CHECK-FIXES: template <typename T, typename = typename std::enable_if<T::some_value>::type>
+// CHECK-FIXES-CXX20: template <typename T, typename = typename std::enable_if<T::some_value>::type>
+
 template <typename T, typename = std::enable_if<T::some_value>>
 struct InvalidClass {};
 // CHECK-MESSAGES: [[@LINE-2]]:23: warning: incorrect std::enable_if usage detected; use 'typename std::enable_if<...>::type' [bugprone-incorrect-enable-if]