[clang-tidy] Add new check 'bugprone-inconsistent-ifelse-braces'

clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp

@@ -33,6 +33,7 @@
 #include "ImplicitWideningOfMultiplicationResultCheck.h"
 #include "InaccurateEraseCheck.h"
 #include "IncDecInConditionsCheck.h"
+#include "InconsistentIfelseBracesCheck.h"
 #include "IncorrectEnableIfCheck.h"
 #include "IncorrectEnableSharedFromThisCheck.h"
 #include "IncorrectRoundingsCheck.h"
@@ -150,6 +151,8 @@ class BugproneModule : public ClangTidyModule {
         "bugprone-implicit-widening-of-multiplication-result");
     CheckFactories.registerCheck<InaccurateEraseCheck>(
         "bugprone-inaccurate-erase");
+    CheckFactories.registerCheck<InconsistentIfelseBracesCheck>(
+        "bugprone-inconsistent-ifelse-braces");
     CheckFactories.registerCheck<IncorrectEnableIfCheck>(
         "bugprone-incorrect-enable-if");
     CheckFactories.registerCheck<IncorrectEnableSharedFromThisCheck>(

clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt

@@ -28,6 +28,7 @@ add_clang_library(clangTidyBugproneModule STATIC
   ForwardingReferenceOverloadCheck.cpp
   ImplicitWideningOfMultiplicationResultCheck.cpp
   InaccurateEraseCheck.cpp
+  InconsistentIfelseBracesCheck.cpp
   IncorrectEnableIfCheck.cpp
   IncorrectEnableSharedFromThisCheck.cpp
   InvalidEnumDefaultInitializationCheck.cpp

clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.cpp

@@ -0,0 +1,89 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "InconsistentIfelseBracesCheck.h"
+#include "../utils/BracesAroundStatement.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::bugprone {
+
+/// 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();
+  if (isa<CompoundStmt>(Then))
+    return true;
+
+  if (const Stmt *const Else = If->getElse()) {
+    if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
+      return shouldHaveBraces(NestedIf);
+
+    return isa<CompoundStmt>(Else);
+  }
+
+  return false;
+}
+
+void InconsistentIfelseBracesCheck::registerMatchers(MatchFinder *Finder) {
+  Finder->addMatcher(
+      traverse(TK_IgnoreUnlessSpelledInSource,
+               ifStmt(hasElse(anything()),
+                      unless(isConsteval()), // 'if consteval' always has braces
+                      unless(hasParent(ifStmt())))
+                   .bind("if_stmt")),
+      this);
+}
+
+void InconsistentIfelseBracesCheck::check(
+    const MatchFinder::MatchResult &Result) {
+  const auto *MatchedIf = Result.Nodes.getNodeAs<IfStmt>("if_stmt");
+  if (!shouldHaveBraces(MatchedIf))
+    return;
+  checkIfStmt(Result, MatchedIf);
+}
+
+void InconsistentIfelseBracesCheck::checkIfStmt(
+    const ast_matchers::MatchFinder::MatchResult &Result, const IfStmt *If) {
+  const Stmt *Then = 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.
+    checkStmt(Result, If->getThen(), If->getRParenLoc(), If->getElseLoc());
+    if (shouldHaveBraces(NestedIf))
+      checkIfStmt(Result, NestedIf);
+  } else if (!isa<CompoundStmt>(Then)) {
+    checkStmt(Result, If->getThen(), If->getRParenLoc(), If->getElseLoc());
+  }
+
+  if (const Stmt *const Else = If->getElse()) {
+    if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
+      checkIfStmt(Result, NestedIf);
+    else if (!isa<CompoundStmt>(Else))
+      checkStmt(Result, If->getElse(), If->getElseLoc());
+  }
+}
+
+void InconsistentIfelseBracesCheck::checkStmt(
+    const ast_matchers::MatchFinder::MatchResult &Result, const Stmt *S,
+    SourceLocation StartLoc, SourceLocation EndLocHint) {
+  const SourceManager &SM = *Result.SourceManager;
+  const LangOptions &LangOpts = Result.Context->getLangOpts();
+
+  const utils::BraceInsertionHints Hints =
+      utils::getBraceInsertionsHints(S, LangOpts, SM, StartLoc, EndLocHint);
+  if (Hints) {
+    DiagnosticBuilder Diag = diag(Hints.DiagnosticPos, "<message>");
+    if (Hints.offersFixIts()) {
+      Diag << Hints.openingBraceFixIt() << Hints.closingBraceFixIt();
+    }
+  }
+}
+
+} // namespace clang::tidy::bugprone

clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.h

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INCONSISTENTIFELSEBRACESCHECK_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INCONSISTENTIFELSEBRACESCHECK_H
+
+#include "../ClangTidyCheck.h"
+
+namespace clang::tidy::bugprone {
+
+/// Detects `if`/`else` statements where one branch uses braces and the other
+/// does not.
+///
+/// For the user-facing documentation see:
+/// https://clang.llvm.org/extra/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.html
+class InconsistentIfelseBracesCheck : public ClangTidyCheck {
+public:
+  InconsistentIfelseBracesCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+  void checkIfStmt(const ast_matchers::MatchFinder::MatchResult &Result,
+                   const IfStmt *If);
+  void checkStmt(const ast_matchers::MatchFinder::MatchResult &Result,
+                 const Stmt *S, SourceLocation StartLoc,
+                 SourceLocation EndLocHint = {});
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INCONSISTENTIFELSEBRACESCHECK_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -157,6 +157,12 @@ Improvements to clang-tidy
 New checks
 ^^^^^^^^^^
 
+- New :doc:`bugprone-inconsistent-ifelse-braces
+  <clang-tidy/checks/bugprone/inconsistent-ifelse-braces>` check.
+
+  Detects ``if``/``else`` statements where one branch uses braces and the other
+  does not.
+
 - New :doc:`bugprone-invalid-enum-default-initialization
   <clang-tidy/checks/bugprone/invalid-enum-default-initialization>` check.
 

clang-tools-extra/docs/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.rst

@@ -0,0 +1,42 @@
+.. title:: clang-tidy - bugprone-inconsistent-ifelse-braces
+
+bugprone-inconsistent-ifelse-braces
+===================================
+
+Detects ``if``/``else`` statements where one branch uses braces and the other
+does not.
+
+Before:
+
+.. code-block:: c++
+
+  if (condition) {
+    statement;
+  } else
+    statement;
+
+  if (condition)
+    statement;
+
+  if (condition)
+    statement;
+  else
+    statement;
+
+After:
+
+.. code-block:: c++
+
+  if (condition) {
+    statement;
+  } else {
+    statement;
+  }
+
+  if (condition)
+    statement;
+
+  if (condition)
+    statement;
+  else
+    statement;

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -101,6 +101,7 @@ Clang-Tidy Checks
    :doc:`bugprone-implicit-widening-of-multiplication-result <bugprone/implicit-widening-of-multiplication-result>`, "Yes"
    :doc:`bugprone-inaccurate-erase <bugprone/inaccurate-erase>`, "Yes"
    :doc:`bugprone-inc-dec-in-conditions <bugprone/inc-dec-in-conditions>`,
+   :doc:`bugprone-inconsistent-ifelse-braces <bugprone/inconsistent-ifelse-braces>`, "Yes"
    :doc:`bugprone-incorrect-enable-if <bugprone/incorrect-enable-if>`, "Yes"
    :doc:`bugprone-incorrect-enable-shared-from-this <bugprone/incorrect-enable-shared-from-this>`, "Yes"
    :doc:`bugprone-incorrect-roundings <bugprone/incorrect-roundings>`,

clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces-consteval-if.cpp

@@ -0,0 +1,54 @@
+// RUN: %check_clang_tidy -std=c++23-or-later %s bugprone-inconsistent-ifelse-braces %t
+
+bool cond(const char *) { return false; }
+void do_something(const char *) {}
+
+// Positive tests.
+void f() {
+  if consteval {
+    if (cond("if1"))
+      do_something("if-single-line");
+    else {
+    }
+    // CHECK-MESSAGES: :[[@LINE-4]]:21: warning: <message> [bugprone-inconsistent-ifelse-braces]
+    // CHECK-FIXES: if (cond("if1")) {
+    // CHECK-FIXES: } else {
+  }
+
+  if consteval {
+    if (cond("if2"))
+      do_something("if-single-line");
+    else {
+    }
+    // CHECK-MESSAGES: :[[@LINE-4]]:21: warning: <message> [bugprone-inconsistent-ifelse-braces]
+    // CHECK-FIXES: if (cond("if2")) {
+    // CHECK-FIXES: } else {
+  } else {
+    if (cond("if2.1")) {
+    } else
+      do_something("else-single-line");
+    // CHECK-MESSAGES: :[[@LINE-2]]:11: warning: <message> [bugprone-inconsistent-ifelse-braces]
+    // CHECK-FIXES: } else {
+    // CHECK-FIXES: }
+  }
+}
+
+// Negative tests.
+void g() {
+  if consteval {
+    if (cond("if0")) {
+      do_something("if-single-line");
+    } else if (cond("if0")) {
+      do_something("elseif-single-line");
+    } else {
+      do_something("else-single-line");
+    }
+  } else {
+    if (cond("if0.1"))
+      do_something("if-single-line");
+    else if (cond("if0.1"))
+      do_something("elseif-single-line");
+    else
+      do_something("else-single-line");
+  }
+}

clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces-constexpr-if.cpp

@@ -0,0 +1,122 @@
+// RUN: %check_clang_tidy -std=c++17-or-later %s bugprone-inconsistent-ifelse-braces %t
+
+constexpr bool cond(const char *) { return false; }
+constexpr void do_something(const char *) {}
+
+// Positive tests.
+void f() {
+  if constexpr (cond("if0") /*comment*/) do_something("if-same-line");
+  else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-3]]:41: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if0") /*comment*/) { do_something("if-same-line");
+  // CHECK-FIXES: } else {
+
+  if constexpr (cond("if0.1") /*comment*/) {
+  } else do_something("else-same-line");
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else { do_something("else-same-line");
+  // CHECK-FIXES: }
+
+  if constexpr (cond("if1"))
+    do_something("if-single-line");
+  else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-4]]:29: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if1")) {
+  // CHECK-FIXES: } else {
+
+  if constexpr (cond("if1.1")) {
+  } else
+    do_something("else-single-line");
+  // CHECK-MESSAGES: :[[@LINE-2]]:9: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else {
+  // CHECK-FIXES: }
+
+  if constexpr (cond("if2") /*comment*/)
+    // some comment
+    do_something("if-multi-line");
+  else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-5]]:41: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if2") /*comment*/) {
+  // CHECK-FIXES: } else {
+
+  if constexpr (cond("if2.1") /*comment*/) {
+  } else
+    // some comment
+    do_something("else-multi-line");
+  // CHECK-MESSAGES: :[[@LINE-3]]:9: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else {
+  // CHECK-FIXES: }
+
+  if constexpr (cond("if3")) do_something("elseif-same-line");
+  else if constexpr (cond("if3")) {
+  } else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-4]]:29: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if3")) { do_something("elseif-same-line");
+  // CHECK-FIXES: } else if constexpr (cond("if3")) {
+
+  if constexpr (cond("if3.1")) {
+  } else if constexpr (cond("if3.1")) do_something("elseif-same-line");
+  else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-3]]:38: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else if constexpr (cond("if3.1")) { do_something("elseif-same-line");
+  // CHECK-FIXES: } else {
+
+  if constexpr (cond("if3.2")) {
+  } else if constexpr (cond("if3.2")) {
+  } else do_something("else-same-line");
+  // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else { do_something("else-same-line");
+  // CHECK-FIXES: }
+
+  if constexpr (cond("if4-outer"))
+    if constexpr (cond("if4-inner"))
+      do_something("if-single-line");
+    else {
+    }
+  else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-7]]:35: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-MESSAGES: :[[@LINE-7]]:37: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if4-outer")) {
+  // CHECK-FIXES: if constexpr (cond("if4-inner")) {
+  // CHECK-FIXES: } else {
+  // CHECK-FIXES: } else {
+
+  if constexpr (cond("if5"))
+      do_something("if-single-line");
+  else if constexpr (cond("if5")) {
+  }
+  // CHECK-MESSAGES: :[[@LINE-4]]:29: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: if constexpr (cond("if5")) {
+  // CHECK-FIXES: } else if constexpr (cond("if5")) {
+
+  if constexpr (cond("if5.1")) {
+  } else if constexpr (cond("if5.1"))
+      do_something("elseif-single-line");
+  // CHECK-MESSAGES: :[[@LINE-2]]:38: warning: <message> [bugprone-inconsistent-ifelse-braces]
+  // CHECK-FIXES: } else if constexpr (cond("if5.1")) {
+  // CHECK-FIXES: }
+}
+
+// Negative tests.
+void g() {
+  if constexpr (cond("if0")) {
+    do_something("if-single-line");
+  } else if constexpr (cond("if0")) {
+    do_something("elseif-single-line");
+  } else {
+    do_something("else-single-line");
+  }
+
+  if constexpr (cond("if1"))
+    do_something("if-single-line");
+  else if constexpr (cond("if1"))
+    do_something("elseif-single-line");
+  else
+    do_something("else-single-line");
+}