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

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

clang-tools-extra/clang-tidy/readability/BracesAroundStatementsCheck.cpp

@@ -147,7 +147,7 @@ BracesAroundStatementsCheck::findRParenLoc(const IfOrWhileStmt *S,
 bool BracesAroundStatementsCheck::checkStmt(
     const MatchFinder::MatchResult &Result, const Stmt *S,
     SourceLocation StartLoc, SourceLocation EndLocHint) {
-  while (const auto *AS = dyn_cast<AttributedStmt>(S))
+  if (const auto *AS = dyn_cast<AttributedStmt>(S))
     S = AS->getSubStmt();
 
   const auto BraceInsertionHints = utils::getBraceInsertionsHints(

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.
@@ -62,10 +70,11 @@ 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 Stmt *Else = If->getElse()) {
+    Else = ignoreAttributed(Else);
     if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
       checkIfStmt(Result, NestedIf);
     else if (!isa<CompoundStmt>(Else))

clang-tools-extra/clang-tidy/utils/BracesAroundStatement.cpp

@@ -127,12 +127,24 @@ BraceInsertionHints getBraceInsertionsHints(const Stmt *const S,
   if (StartLoc.isInvalid())
     return {};
 
+  const Stmt *InnerS = S;
+  while (const auto *AS = dyn_cast<AttributedStmt>(InnerS))
+    InnerS = AS->getSubStmt();
+
+  SourceLocation InsertLoc = StartLoc;
+  if (S != InnerS) {
+    if (std::optional<Token> Tok = utils::lexer::getPreviousToken(
+            InnerS->getBeginLoc(), SM, LangOpts, /*SkipComments=*/true)) {
+      InsertLoc = Tok->getLocation();
+    }
+  }
+
   // Convert StartLoc to file location, if it's on the same macro expansion
   // level as the start of the statement. We also need file locations for
   // Lexer::getLocForEndOfToken working properly.
-  StartLoc = Lexer::makeFileCharRange(
-                 CharSourceRange::getCharRange(StartLoc, S->getBeginLoc()), SM,
-                 LangOpts)
+  StartLoc = Lexer::makeFileCharRange(CharSourceRange::getCharRange(
+                                          InsertLoc, InnerS->getBeginLoc()),
+                                      SM, LangOpts)
                  .getBegin();
   if (StartLoc.isInvalid())
     return {};

clang-tools-extra/test/clang-tidy/checkers/readability/inconsistent-ifelse-braces-attributes.cpp

@@ -5,15 +5,29 @@ void f(bool b) {
   if (b) [[likely]] return;
   else {
   }
-  // CHECK-MESSAGES: :[[@LINE-3]]:9: warning: statement should have braces [readability-inconsistent-ifelse-braces]
-  // CHECK-FIXES: if (b) { {{[[][[]}}likely{{[]][]]}} return;
+  // CHECK-MESSAGES: :[[@LINE-3]]:20: warning: statement should have braces [readability-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if (b) {{[[][[]}}likely{{[]][]]}} { return;
   // CHECK-FIXES: } else {
 
   if (b) {
   } else [[unlikely]]
     return;
-  // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: statement should have braces [readability-inconsistent-ifelse-braces]
-  // CHECK-FIXES: } else { {{[[][[]}}unlikely{{[]][]]}}
+  // CHECK-MESSAGES: :[[@LINE-2]]:22: warning: statement should have braces [readability-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else {{[[][[]}}unlikely{{[]][]]}} {
+
+  if (b) [[likely]] {
+  } else [[unlikely]]
+    return;
+  // CHECK-MESSAGES: :[[@LINE-2]]:22: warning: statement should have braces [readability-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else {{[[][[]}}unlikely{{[]][]]}} {
+
+  if (b) [[likely]]
+    return;
+  else [[unlikely]] {
+  }
+  // CHECK-MESSAGES: :[[@LINE-4]]:20: 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;
+  }
 }