[clang-tools-extra] [clang-tidy] fix fasle negatives in readability-redundant-casting when cast function pointer (PR #170502)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tools-extra

Author: Congcong Cai (HerrCai0907)

<details>
<summary>Changes</summary>

Part of #<!-- -->170476
When check equal of type, we need to ignore ParenType


---
Full diff: https://github.com/llvm/llvm-project/pull/170502.diff


3 Files Affected:

- (modified) clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp (+2-1) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+4) 
- (modified) clang-tools-extra/test/clang-tidy/checkers/readability/redundant-casting.cpp (+10) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
index d11c41c33d2be..21f481a718219 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
@@ -9,6 +9,7 @@
 #include "RedundantCastingCheck.h"
 #include "../utils/FixItHintUtils.h"
 #include "clang/AST/ASTContext.h"
+#include "clang/AST/TypeBase.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Lex/Lexer.h"
 
@@ -29,7 +30,7 @@ static bool areTypesEqual(QualType S, QualType D) {
   const QualType PtrD = D->getPointeeType();
 
   if (!PtrS.isNull() && !PtrD.isNull())
-    return areTypesEqual(PtrS, PtrD);
+    return areTypesEqual(PtrS.IgnoreParens(), PtrD.IgnoreParens());
 
   const DeducedType *DT = S->getContainedDeducedType();
   if (DT && DT->isDeduced())
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 9533d56c219f7..b4d8c02a852a1 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -562,6 +562,10 @@ 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-casting
+  <clang-tidy/checks/readability/redundant-casting>` check by fixing false
+  negatives when explicitly cast from function pointer.
+
 - 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-casting.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-casting.cpp
index fa91995c5615f..3e723b8b61d1d 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-casting.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/redundant-casting.cpp
@@ -235,3 +235,13 @@ void testRedundantDependentNTTPCasting() {
   // CHECK-MESSAGES: :[[@LINE-4]]:25: note: source type originates from referencing this non-type template parameter
   // CHECK-FIXES: T a = V;
 }
+
+namespace gh170476 {
+int f(void);
+int g1() {
+  int (*fp)() = (int(*)(void))&f;
+  // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: redundant explicit casting to the same type 'int (*)()' as the sub-expression, remove this casting [readability-redundant-casting]
+  // CHECK-FIXES: int (*fp)() = (&f);
+  return fp();
+}
+} // namespace gh170476

``````````

</details>


https://github.com/llvm/llvm-project/pull/170502