[clang-tools-extra] [clang-tidy] Correctly handle attributes in readability-inconsistent-ifelse-braces (PR #184095)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-tidy

Author: mitchell (zeyi2)

<details>
<summary>Changes</summary>

Improved the check to correctly handle `[[likely]]` and `[[unlikely]]` attributes placed between the if/else keyword and the opening brace.

As of AI Usage: Gemini 3 is used for pre-commit reviewing.
Closes https://github.com/llvm/llvm-project/issues/184081


---
Full diff: https://github.com/llvm/llvm-project/pull/184095.diff


3 Files Affected:

- (modified) clang-tools-extra/clang-tidy/readability/InconsistentIfElseBracesCheck.cpp (+15-6) 
- (modified) clang-tools-extra/docs/ReleaseNotes.rst (+5) 
- (modified) clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp (+46) 


``````````diff
diff --git a/clang-tools-extra/clang-tidy/readability/InconsistentIfElseBracesCheck.cpp b/clang-tools-extra/clang-tidy/readability/InconsistentIfElseBracesCheck.cpp
index 6cc1b203470f1..5cf52088917a9 100644
--- a/clang-tools-extra/clang-tidy/readability/InconsistentIfElseBracesCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/InconsistentIfElseBracesCheck.cpp
@@ -18,13 +18,21 @@ using namespace clang::ast_matchers;
 
 namespace clang::tidy::readability {
 
+/// Look through AttributedStmt wrappers to find the underlying statement.
+static const Stmt *ignoreAttributed(const Stmt *S) {
+  if (const auto *AS = dyn_cast<AttributedStmt>(S))
+    return AS->getSubStmt();
+  return S;
+}
+
 /// Check that at least one branch of the \p If statement is a \c CompoundStmt.
 static bool shouldHaveBraces(const IfStmt *If) {
-  const Stmt *const Then = If->getThen();
+  const Stmt *const Then = ignoreAttributed(If->getThen());
   if (isa<CompoundStmt>(Then))
     return true;
 
-  if (const Stmt *const Else = If->getElse()) {
+  if (const Stmt *Else = If->getElse()) {
+    Else = ignoreAttributed(Else);
     if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
       return shouldHaveBraces(NestedIf);
 
@@ -53,7 +61,7 @@ void InconsistentIfElseBracesCheck::check(
 
 void InconsistentIfElseBracesCheck::checkIfStmt(
     const MatchFinder::MatchResult &Result, const IfStmt *If) {
-  const Stmt *Then = If->getThen();
+  const Stmt *Then = ignoreAttributed(If->getThen());
   if (const auto *NestedIf = dyn_cast<const IfStmt>(Then)) {
     // If the then-branch is a nested IfStmt, first we need to add braces to
     // it, then we need to check the inner IfStmt.
@@ -62,13 +70,14 @@ void InconsistentIfElseBracesCheck::checkIfStmt(
     if (shouldHaveBraces(NestedIf))
       checkIfStmt(Result, NestedIf);
   } else if (!isa<CompoundStmt>(Then)) {
-    emitDiagnostic(Result, Then, If->getRParenLoc(), If->getElseLoc());
+    emitDiagnostic(Result, If->getThen(), If->getRParenLoc(), If->getElseLoc());
   }
 
   if (const Stmt *const Else = If->getElse()) {
-    if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
+    const Stmt *UnwrappedElse = ignoreAttributed(Else);
+    if (const auto *NestedIf = dyn_cast<const IfStmt>(UnwrappedElse))
       checkIfStmt(Result, NestedIf);
-    else if (!isa<CompoundStmt>(Else))
+    else if (!isa<CompoundStmt>(UnwrappedElse))
       emitDiagnostic(Result, If->getElse(), If->getElseLoc());
   }
 }
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index cf8dd0dba9f12..65a24f1311754 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -253,6 +253,11 @@ Changes in existing checks
   now uses separate note diagnostics for each uninitialized enumerator, making
   it easier to see which specific enumerators need explicit initialization.
 
+- Improved :doc:`readability-inconsistent-ifelse-braces
+  <clang-tidy/checks/readability/inconsistent-ifelse-braces>` check by fixing
+  false positives when ``[[likely]]`` or ``[[unlikely]]`` attributes are placed
+  between the ``if`` or ``else`` keyword and the opening brace.
+
 - Improved :doc:`readability-non-const-parameter
   <clang-tidy/checks/readability/non-const-parameter>` check by avoiding false
   positives on parameters used in dependent expressions (e.g. inside generic
diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp
index 8fdb574227028..8e44440669d40 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp
@@ -14,6 +14,20 @@ void f(bool b) {
     return;
   // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: statement should have braces [readability-inconsistent-ifelse-braces]
   // CHECK-FIXES: } else { {{[[][[]}}unlikely{{[]][]]}}
+
+  if (b) [[likely]] {
+  } else [[unlikely]]
+    return;
+  // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: statement should have braces [readability-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else { {{[[][[]}}unlikely{{[]][]]}}
+
+  if (b) [[likely]]
+    return;
+  else [[unlikely]] {
+  }
+  // CHECK-MESSAGES: :[[@LINE-4]]:9: warning: statement should have braces [readability-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if (b) { {{[[][[]}}likely{{[]][]]}}
+  // CHECK-FIXES: } else {{[[][[]}}unlikely{{[]][]]}} {
 }
 
 // Negative tests.
@@ -39,4 +53,36 @@ void g(bool b) {
     return;
   else [[likely]]
     return;
+
+  if (b) [[likely]] {
+    return;
+  } else {
+    return;
+  }
+
+  if (b) {
+    return;
+  } else [[unlikely]] {
+    return;
+  }
+
+  if (b) [[likely]] {
+    return;
+  } else [[unlikely]] {
+    return;
+  }
+
+  if (b) [[likely]] {
+    return;
+  } else if (b) [[unlikely]] {
+    return;
+  } else {
+    return;
+  }
+
+  if (b) [[likely]] [[likely]] {
+    return;
+  } else [[unlikely]] [[unlikely]] {
+    return;
+  }
 }

``````````

</details>


https://github.com/llvm/llvm-project/pull/184095