[clang-tools-extra] 6c153e5 - [clang-tidy] Fix false positives with template in `misc-unconventional-assign-operator` check (#143292)

[via cfe-commits]

Author: flovent
Date: 2025-07-06T15:06:18+03:00
New Revision: 6c153e50f8b23dbd422c3f9eedf65344839bbbb1

URL: https://github.com/llvm/llvm-project/commit/6c153e50f8b23dbd422c3f9eedf65344839bbbb1
DIFF: https://github.com/llvm/llvm-project/commit/6c153e50f8b23dbd422c3f9eedf65344839bbbb1.diff

LOG: [clang-tidy] Fix false positives with template in `misc-unconventional-assign-operator` check (#143292)

Fix false positives when copy assignment operator function in a template
class returns the result of another assignment to `*this`, this check
doesn't consider this situation that there will be a `BinaryOperator`
for assignment rather than `CXXOperatorCallExpr` since `this`'s type is
dependent.

Closes #143237.

Added: 
    

Modified: 
    clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
    clang-tools-extra/docs/ReleaseNotes.rst
    clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp

Removed: 
    


################################################################################
diff  --git a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
index afc4897eeb2ae..3fdaf9239f6af 100644
--- a/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
+++ b/clang-tools-extra/clang-tidy/misc/UnconventionalAssignOperatorCheck.cpp
@@ -66,8 +66,11 @@ void UnconventionalAssignOperatorCheck::registerMatchers(
                                 hasArgument(0, cxxThisExpr())),
             cxxOperatorCallExpr(
                 hasOverloadedOperatorName("="),
-                hasArgument(
-                    0, unaryOperator(hasOperatorName("*"),
+                hasArgument(0, unaryOperator(hasOperatorName("*"),
+                                             hasUnaryOperand(cxxThisExpr())))),
+            binaryOperator(
+                hasOperatorName("="),
+                hasLHS(unaryOperator(hasOperatorName("*"),
                                      hasUnaryOperand(cxxThisExpr())))))))));
   const auto IsGoodAssign = cxxMethodDecl(IsAssign, HasGoodReturnType);
 

diff  --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index f8f183e9de1cc..e021d6350694e 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -266,6 +266,11 @@ Changes in existing checks
   <clang-tidy/checks/misc/redundant-expression>` check by providing additional
   examples and fixing some macro related false positives.
 
+- Improved :doc:`misc-unconventional-assign-operator
+  <clang-tidy/checks/misc/unconventional-assign-operator>` check by fixing
+  false positives when copy assignment operator function in a template class
+  returns the result of another assignment to ``*this`` (``return *this=...``).
+
 - Improved :doc:`misc-unused-using-decls
   <clang-tidy/checks/misc/unused-using-decls>` check by fixing false positives
   on ``operator""`` with template parameters.

diff  --git a/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp b/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
index 74a22a7c083f4..28b53ae4af63d 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/misc/unconventional-assign-operator.cpp
@@ -163,3 +163,16 @@ struct TemplateTypeAlias {
   Alias3<TypeAlias::Alias> &operator=(double) { return *this; }
   // CHECK-MESSAGES: :[[@LINE-1]]:3: warning: operator=() should return 'TemplateTypeAlias&' [misc-unconventional-assign-operator]
 };
+
+namespace gh143237 {
+template<typename T>
+struct TemplateAssignment {
+  explicit TemplateAssignment(int) {
+  }
+
+  TemplateAssignment& operator=(int n) {
+    // No warning
+    return *this = TemplateAssignment(n);
+  }
+};
+}