[clang-tools-extra] [clang-tidy] Add new check 'bugprone-inconsistent-ifelse-braces' (PR #162361)
Davide Cunial via cfe-commits
cfe-commits at lists.llvm.org
Wed Oct 8 11:24:58 PDT 2025
https://github.com/capitan-davide updated https://github.com/llvm/llvm-project/pull/162361
>From 29e7a6a80aa1d4e24a6a59af5b033712fe912f3e Mon Sep 17 00:00:00 2001
From: Davide Cunial <dcunial at proton.me>
Date: Wed, 8 Oct 2025 20:24:17 +0200
Subject: [PATCH] [clang-tidy] Add new check
'bugprone-inconsistent-ifelse-braces'
---
.../bugprone/BugproneTidyModule.cpp | 3 +
.../clang-tidy/bugprone/CMakeLists.txt | 1 +
.../InconsistentIfelseBracesCheck.cpp | 63 +++++++++++++++++++
.../bugprone/InconsistentIfelseBracesCheck.h | 34 ++++++++++
clang-tools-extra/docs/ReleaseNotes.rst | 5 ++
.../bugprone/inconsistent-ifelse-braces.rst | 6 ++
.../docs/clang-tidy/checks/list.rst | 3 +-
.../bugprone/inconsistent-ifelse-braces.cpp | 52 +++++++++++++++
8 files changed, 166 insertions(+), 1 deletion(-)
create mode 100644 clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.cpp
create mode 100644 clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.h
create mode 100644 clang-tools-extra/docs/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.rst
create mode 100644 clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces.cpp
diff --git a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp b/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
index fe261e729539c..e1e42d22c520e 100644
--- a/clang-tools-extra/clang-tidy/bugprone/BugproneTidyModule.cpp
+++ b/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>(
diff --git a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt b/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
index 46bc8efd44bc5..d19fd5017d2e0 100644
--- a/clang-tools-extra/clang-tidy/bugprone/CMakeLists.txt
+++ b/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
diff --git a/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.cpp b/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.cpp
new file mode 100644
index 0000000000000..b695467977c4f
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.cpp
@@ -0,0 +1,63 @@
+
+//===----------------------------------------------------------------------===//
+//
+// 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 "clang/AST/ASTTypeTraits.h"
+#include "clang/AST/Stmt.h"
+#include "clang/ASTMatchers/ASTMatchFinder.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;
+
+ const Stmt *const Else = If->getElse();
+ if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
+ return shouldHaveBraces(NestedIf);
+
+ return isa<CompoundStmt>(Else);
+}
+
+/// Check that all branchs of the \p If statement is are \c CompoundStmt.
+static bool doesHaveBraces(const IfStmt *If) {
+ const Stmt *const Then = If->getThen();
+ if (!isa<CompoundStmt>(Then))
+ return false;
+
+ const Stmt *const Else = If->getElse();
+ if (const auto *NestedIf = dyn_cast<const IfStmt>(Else))
+ return doesHaveBraces(NestedIf);
+
+ return isa<CompoundStmt>(Else);
+}
+
+void InconsistentIfelseBracesCheck::registerMatchers(MatchFinder *Finder) {
+ Finder->addMatcher(
+ traverse(TK_IgnoreUnlessSpelledInSource,
+ ifStmt(hasElse(anything()), 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) && !doesHaveBraces(MatchedIf)) {
+ diag(MatchedIf->getBeginLoc(), "bad!") << MatchedIf->getSourceRange();
+ }
+}
+
+} // namespace clang::tidy::bugprone
diff --git a/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.h b/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.h
new file mode 100644
index 0000000000000..9f0848cff8a43
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/bugprone/InconsistentIfelseBracesCheck.h
@@ -0,0 +1,34 @@
+
+//===----------------------------------------------------------------------===//
+//
+// 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 {
+
+/// FIXME: Write a short description.
+///
+/// For the user-facing documentation see:
+/// http://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;
+ bool isLanguageVersionSupported(const LangOptions &LangOpts) const override {
+ return LangOpts.CPlusPlus;
+ }
+};
+
+} // namespace clang::tidy::bugprone
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_BUGPRONE_INCONSISTENTIFELSEBRACESCHECK_H
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 7cdff86beeec6..6ed9b93e8c226 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -157,6 +157,11 @@ Improvements to clang-tidy
New checks
^^^^^^^^^^
+- New :doc:`bugprone-inconsistent-ifelse-braces
+ <clang-tidy/checks/bugprone/inconsistent-ifelse-braces>` check.
+
+ FIXME: Write a short description.
+
- New :doc:`bugprone-invalid-enum-default-initialization
<clang-tidy/checks/bugprone/invalid-enum-default-initialization>` check.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.rst b/clang-tools-extra/docs/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.rst
new file mode 100644
index 0000000000000..9592f39d6a13d
--- /dev/null
+++ b/clang-tools-extra/docs/clang-tidy/checks/bugprone/inconsistent-ifelse-braces.rst
@@ -0,0 +1,6 @@
+.. title:: clang-tidy - bugprone-inconsistent-ifelse-braces
+
+bugprone-inconsistent-ifelse-braces
+===================================
+
+FIXME: Describe what patterns does the check detect and why. Give examples.
diff --git a/clang-tools-extra/docs/clang-tidy/checks/list.rst b/clang-tools-extra/docs/clang-tidy/checks/list.rst
index c490d2ece2e0a..9438030c64828 100644
--- a/clang-tools-extra/docs/clang-tidy/checks/list.rst
+++ b/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>`,
: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>`,
@@ -256,7 +257,7 @@ Clang-Tidy Checks
:doc:`llvm-prefer-static-over-anonymous-namespace <llvm/prefer-static-over-anonymous-namespace>`,
:doc:`llvm-twine-local <llvm/twine-local>`, "Yes"
:doc:`llvm-use-new-mlir-op-builder <llvm/use-new-mlir-op-builder>`, "Yes"
- :doc:`llvm-use-ranges <llvm/use-ranges>`, "Yes"
+ :doc:`llvm-use-ranges <llvm/use-ranges>`,
:doc:`llvmlibc-callee-namespace <llvmlibc/callee-namespace>`,
:doc:`llvmlibc-implementation-in-namespace <llvmlibc/implementation-in-namespace>`,
:doc:`llvmlibc-inline-function-decl <llvmlibc/inline-function-decl>`, "Yes"
diff --git a/clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces.cpp b/clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces.cpp
new file mode 100644
index 0000000000000..2a281193814dc
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/bugprone/inconsistent-ifelse-braces.cpp
@@ -0,0 +1,52 @@
+// RUN: %check_clang_tidy %s bugprone-inconsistent-ifelse-braces %t
+
+void foo(bool flag) {
+ int x, y;
+
+ if (flag)
+ x = 0;
+ else {
+ y = 1;
+ }
+
+ if (flag) {
+ x = 2;
+ } else {
+ y = 3;
+ }
+
+ if (flag) {
+ x = 4;
+ } else if (flag) {
+ x = 5;
+ } else {
+ y = 6;
+ }
+
+ if (flag)
+ x = 7;
+ else if (flag)
+ y = 8;
+ else
+ y = 9;
+
+ if (flag)
+ x = 10;
+ else if (flag) {
+ y = 11;
+ } else
+ y = 12;
+}
+
+// FIXME: Add something that triggers the check here.
+void f();
+// CHECK-MESSAGES: :[[@LINE-1]]:6: warning: function 'f' is insufficiently awesome [bugprone-inconsistent-ifelse-braces]
+
+// FIXME: Verify the applied fix.
+// * Make the CHECK patterns specific enough and try to make verified lines
+// unique to avoid incorrect matches.
+// * Use {{}} for regular expressions.
+// CHECK-FIXES: {{^}}void awesome_f();{{$}}
+
+// FIXME: Add something that doesn't trigger the check here.
+void awesome_f2();
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