[clang-tidy] Fix if-constexpr false-positive in readability-misleading-indentation

When  depend on template parameter,
compiler can use NullStmt instead of CompoundStmt.
This causes issues as we losing information about
end location of that Stmt. To avoid this issue
check now ignores ifStmt with NullStmt on true-branch.

Fixes: https://github.com/llvm/llvm-project/issues/61435

Reviewed By: carlosgalvezp

Differential Revision: https://reviews.llvm.org/D146887

diff --git a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
index 4c10b6f..2c011f5 100644 (file)
--- a/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/MisleadingIndentationCheck.cpp
@@ -104,7 +104,8 @@ void MisleadingIndentationCheck::missingBracesCheck(const SourceManager &SM,
 }
 
 void MisleadingIndentationCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(ifStmt(hasElse(stmt())).bind("if"), this);
+  Finder->addMatcher(
+      ifStmt(unless(hasThen(nullStmt())), hasElse(stmt())).bind("if"), this);
   Finder->addMatcher(
       compoundStmt(has(stmt(anyOf(ifStmt(), forStmt(), whileStmt()))))
           .bind("compound"),

diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 03ba9e1..413f892 100644 (file)
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -240,6 +240,10 @@ Changes in existing checks
   magic numbers in type aliases such as ``using`` and ``typedef`` declarations if
   the new ``IgnoreTypeAliases`` option is set to true.
 
+- Fixed a false positive in :doc:`readability-misleading-indentation
+  <clang-tidy/checks/readability/misleading-indentation>` check when warning would
+  be unnecessarily emitted for template dependent ``if constexpr``.
+
 - Fixed a false positive in :doc:`cppcoreguidelines-slicing
   <clang-tidy/checks/cppcoreguidelines/slicing>` check when warning would be
   emitted in constructor for virtual base class initialization.

diff --git a/clang-tools-extra/test/clang-tidy/checkers/readability/misleading-indentation-cpp17.cpp b/clang-tools-extra/test/clang-tidy/checkers/readability/misleading-indentation-cpp17.cpp
new file mode 100644 (file)
index 0000000..31e3893
--- /dev/null
+++ b/clang-tools-extra/test/clang-tidy/checkers/readability/misleading-indentation-cpp17.cpp
@@ -0,0 +1,29 @@
+// RUN: %check_clang_tidy -std=c++17-or-later %s readability-misleading-indentation %t -- -- -fno-delayed-template-parsing
+
+namespace PR61435 {
+
+template<int N>
+constexpr auto lam_correct = []{
+  if constexpr (N == 1) {
+  } else {
+  }
+};
+
+template<int N>
+constexpr auto lam_incorrect = []{
+  if constexpr (N == 1) {
+  }
+   else {
+  }
+  // CHECK-MESSAGES: :[[@LINE-2]]:4: warning: different indentation for 'if' and corresponding 'else' [readability-misleading-indentation]
+};
+
+void test() {
+  lam_correct<1>();
+  lam_correct<2>();
+
+  lam_incorrect<1>();
+  lam_incorrect<2>();
+}
+
+}