[clang-tidy] Improve ExceptionSpecAnalyzers handling of conditional noexcept expressions

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

@@ -142,13 +142,22 @@ ExceptionSpecAnalyzer::analyzeFunctionEST(const FunctionDecl *FuncDecl,
     return State::NotThrowing;
   case CT_Dependent: {
     const Expr *NoexceptExpr = FuncProto->getNoexceptExpr();
+    if (!NoexceptExpr)
+      return State::NotThrowing;
+
+    // We can't resolve value dependence so just return unknown
+    if (NoexceptExpr->isValueDependent())
+      return State::Unknown;
+
+    // Try to evaluate the expression to a boolean value
     bool Result = false;
-    return (NoexceptExpr && !NoexceptExpr->isValueDependent() &&
-            NoexceptExpr->EvaluateAsBooleanCondition(
-                Result, FuncDecl->getASTContext(), true) &&
-            Result)
-               ? State::NotThrowing
-               : State::Throwing;
+    if (NoexceptExpr->EvaluateAsBooleanCondition(
+            Result, FuncDecl->getASTContext(), true))
+      return Result ? State::NotThrowing : State::Throwing;
+
+    // The noexcept expression is not value dependent but we can't evaluate it
+    // as a boolean condition so we have no idea if its throwing or not
+    return State::Unknown;
   }
   default:
     return State::Throwing;

clang-tools-extra/docs/ReleaseNotes.rst

@@ -284,9 +284,14 @@ Changes in existing checks
   <clang-tidy/checks/performance/faster-string-find>` check to properly escape
   single quotes.
 
+- Improved :doc:`performance-noexcept-move-constructor
+  <clang-tidy/checks/performance/noexcept-move-constructor>` to better handle
+  conditional noexcept expressions, eliminating false-positives.
+
 - Improved :doc:`performance-noexcept-swap
   <clang-tidy/checks/performance/noexcept-swap>` check to enforce a stricter
-  match with the swap function signature, eliminating false-positives.
+  match with the swap function signature and better handling of condition
+  noexcept expressions, eliminating false-positives.
 
 - Improved :doc:`readability-braces-around-statements
   <clang-tidy/checks/readability/braces-around-statements>` check to

clang-tools-extra/test/clang-tidy/checkers/performance/noexcept-move-constructor.cpp

@@ -1,5 +1,14 @@
 // RUN: %check_clang_tidy %s performance-noexcept-move-constructor %t -- -- -fexceptions
 
+namespace std
+{
+  template <typename T>
+  struct is_nothrow_move_constructible
+  {
+    static constexpr bool value = __is_nothrow_constructible(T, __add_rvalue_reference(T));
+  };
+} // namespace std
+
 struct Empty
 {};
 
@@ -379,3 +388,12 @@ struct OK31 {
   OK31(OK31 &&) noexcept(TrueT<int>::value) = default;
   OK31& operator=(OK31 &&) noexcept(TrueT<int>::value) = default;
 };
+
+namespace gh68101
+{
+  template <typename T>
+  class Container {
+     public:
+      Container(Container&&) noexcept(std::is_nothrow_move_constructible<T>::value);
+  };
+} // namespace gh68101

clang-tools-extra/test/clang-tidy/checkers/performance/noexcept-swap.cpp

@@ -1,5 +1,14 @@
 // RUN: %check_clang_tidy %s performance-noexcept-swap %t -- -- -fexceptions
 
+namespace std
+{
+  template <typename T>
+  struct is_nothrow_move_constructible
+  {
+    static constexpr bool value = __is_nothrow_constructible(T, __add_rvalue_reference(T));
+  };
+} // namespace std
+
 void throwing_function() noexcept(false);
 void noexcept_function() noexcept;
 
@@ -54,9 +63,6 @@ struct D {
   // CHECK-MESSAGES: :[[@LINE-1]]:27: warning: noexcept specifier on swap function evaluates to 'false' [performance-noexcept-swap]
 };
 
-template <typename T>
-void swap(D<T> &, D<T> &) noexcept(D<T>::kFalse);
-// CHECK-MESSAGES: :[[@LINE-1]]:36: warning: noexcept specifier on swap function evaluates to 'false' [performance-noexcept-swap]
 void swap(D<int> &, D<int> &) noexcept(D<int>::kFalse);
 // CHECK-MESSAGES: :[[@LINE-1]]:40: warning: noexcept specifier on swap function evaluates to 'false' [performance-noexcept-swap]
 
@@ -151,9 +157,8 @@ struct OK16 {
   void swap(OK16 &) noexcept(kTrue);
 };
 
-// FIXME: This gives a warning, but it should be OK.
-//template <typename T>
-//void swap(OK16<T> &, OK16<T> &) noexcept(OK16<T>::kTrue);
+template <typename T>
+void swap(OK16<T> &, OK16<T> &) noexcept(OK16<T>::kTrue);
 template <typename T>
 void swap(OK16<int> &, OK16<int> &) noexcept(OK16<int>::kTrue);
 
@@ -217,4 +222,13 @@ namespace PR64303 {
     friend void swap(Test&, Test&);
     // CHECK-MESSAGES: :[[@LINE-1]]:17: warning: swap functions should be marked noexcept [performance-noexcept-swap]
   };
-}
+} // namespace PR64303
+
+namespace gh68101
+{
+  template <typename T>
+  class Container {
+     public:
+      void swap(Container&) noexcept(std::is_nothrow_move_constructible<T>::value);
+  };
+} // namespace gh68101