[clang-tidy] exclude CXXParenListInitExpr from RedundantCastingCheck

[dl8sd11]

Exclude CXXParenListInitExpr from RedundantCastingCheck because there are false positive cases. Currently, we can't think of positive cases for CXXParenListInitExpr. This can be improved by following the initListExpr method if we can come up with some positive cases.

Fixes #108846

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[llvmbot]

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

@llvm/pr-subscribers-clang-tidy

Author: Tommy Chen (dl8sd11)

Changes

Exclude CXXParenListInitExpr from RedundantCastingCheck because there are false positive cases. Currently, we can't think of positive cases for CXXParenListInitExpr. This can be improved by following the initListExpr method if we can come up with some positive cases.

#108846

---

Full diff: https://github.com/llvm/llvm-project/pull/109741.diff

2 Files Affected:

• (modified) clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp (+5)
• (modified) clang-tools-extra/test/clang-tidy/checkers/readability/redundant-casting.cpp (+7-3)

diff --git a/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp b/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
index b9ff0e81cbc522..fb85eb1628afbd 100644
--- a/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/RedundantCastingCheck.cpp
@@ -108,6 +108,10 @@ void RedundantCastingCheck::registerMatchers(MatchFinder *Finder) {
 
   auto BitfieldMemberExpr = memberExpr(member(fieldDecl(isBitField())));
 
+  const ast_matchers::internal::VariadicDynCastAllOfMatcher<
+      Stmt, CXXParenListInitExpr>
+      cxxParenListInitExpr; // NOLINT(readability-identifier-naming)
+
   Finder->addMatcher(
       explicitCastExpr(
           unless(hasCastKind(CK_ConstructorConversion)),
@@ -117,6 +121,7 @@ void RedundantCastingCheck::registerMatchers(MatchFinder *Finder) {
           hasDestinationType(qualType().bind("dstType")),
           hasSourceExpression(anyOf(
               expr(unless(initListExpr()), unless(BitfieldMemberExpr),
+                   unless(cxxParenListInitExpr()),
                    hasType(qualType().bind("srcType")))
                   .bind("source"),
               initListExpr(unless(hasInit(1, expr())),
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 30cac6bd5cca06..d94452d84a5841 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
@@ -1,8 +1,8 @@
-// RUN: %check_clang_tidy -std=c++11-or-later %s readability-redundant-casting %t -- -- -fno-delayed-template-parsing
-// RUN: %check_clang_tidy -std=c++11-or-later -check-suffix=,MACROS %s readability-redundant-casting %t -- \
+// RUN: %check_clang_tidy -std=c++20-or-later %s readability-redundant-casting %t -- -- -fno-delayed-template-parsing
+// RUN: %check_clang_tidy -std=c++20-or-later -check-suffix=,MACROS %s readability-redundant-casting %t -- \
 // RUN:   -config='{CheckOptions: { readability-redundant-casting.IgnoreMacros: false }}' \
 // RUN:   -- -fno-delayed-template-parsing
-// RUN: %check_clang_tidy -std=c++11-or-later -check-suffix=,ALIASES %s readability-redundant-casting %t -- \
+// RUN: %check_clang_tidy -std=c++20-or-later -check-suffix=,ALIASES %s readability-redundant-casting %t -- \
 // RUN:   -config='{CheckOptions: { readability-redundant-casting.IgnoreTypeAliases: true }}' \
 // RUN:   -- -fno-delayed-template-parsing
 
@@ -57,6 +57,10 @@ void testDiffrentTypesCast(B& value) {
   A& a7 = static_cast<A&>(value);
 }
 
+void testParenListInitExpr(A value) {
+  B b = static_cast<B>(value);
+}
+
 void testCastingWithAuto() {
   auto a = getA();
   A& a8 = static_cast<A&>(a);

[EugeneZelenko]

Please mention changes in Release Notes.

[PiotrZSL]

Except single comment, looks fine.

[felix642]

LGTM.

[5chmidti]

Actually, shouldn't this check instead change an explicit cast for a CXXParenListExpr from static_cast<C>(42) to C(42)? Doing this would be fairly simple and there should not be any case that wouldn't support it FWICT.

[PiotrZSL]

Actually, shouldn't this check instead change an explicit cast for a CXXParenListExpr from static_cast<C>(42) to C(42)

Yes, but that's secondary. As in such case this could be seen as an FunctionalCast.

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