[clang-tidy] fix false positive in cppcoreguidelines-missing-std-forward

clang-tools-extra/clang-tidy/cppcoreguidelines/MissingStdForwardCheck.cpp

@@ -53,16 +53,72 @@ AST_MATCHER(ParmVarDecl, isTemplateTypeParameter) {
          FuncTemplate->getTemplateParameters()->getDepth();
 }
 
+AST_MATCHER_P(NamedDecl, hasSameNameAsBoundNode, std::string, BindingID) {
+  IdentifierInfo *II = Node.getIdentifier();
+  if (nullptr == II)
+    return false;
+  StringRef Name = II->getName();
+
+  return Builder->removeBindings(
+      [this, Name](const ast_matchers::internal::BoundNodesMap &Nodes) {
+        const DynTypedNode &BN = Nodes.getNode(this->BindingID);
+        if (const auto *ND = BN.get<NamedDecl>()) {
+          if (!isa<FieldDecl, CXXMethodDecl, VarDecl>(ND))
+            return true;
+          return ND->getName() != Name;
+        }
+        return true;
+      });
+}
+
+AST_MATCHER_P(LambdaCapture, hasCaptureKind, LambdaCaptureKind, Kind) {
+  return Node.getCaptureKind() == Kind;
+}
+
+AST_MATCHER_P(LambdaExpr, hasCaptureDefaultKind, LambdaCaptureDefault, Kind) {
+  return Node.getCaptureDefault() == Kind;
+}
+
 } // namespace
 
 void MissingStdForwardCheck::registerMatchers(MatchFinder *Finder) {
+  auto RefToParmImplicit = allOf(
+      equalsBoundNode("var"), hasInitializer(ignoringParenImpCasts(
+                                  declRefExpr(to(equalsBoundNode("param"))))));
+  auto RefToParm = capturesVar(
+      varDecl(anyOf(hasSameNameAsBoundNode("param"), RefToParmImplicit)));
+  auto HasRefToParm = hasAnyCapture(RefToParm);
+
+  auto CaptureInRef =
+      allOf(hasCaptureDefaultKind(LambdaCaptureDefault::LCD_ByRef),
+            unless(hasAnyCapture(
+                capturesVar(varDecl(hasSameNameAsBoundNode("param"))))));
+  auto CaptureInCopy = allOf(
+      hasCaptureDefaultKind(LambdaCaptureDefault::LCD_ByCopy), HasRefToParm);
+  auto CaptureByRefExplicit = hasAnyCapture(
+      allOf(hasCaptureKind(LambdaCaptureKind::LCK_ByRef), RefToParm));
+
+  auto CapturedInBody =
+      lambdaExpr(anyOf(CaptureInRef, CaptureInCopy, CaptureByRefExplicit));
+  auto CapturedInCaptureList = hasAnyCapture(capturesVar(
+      varDecl(hasInitializer(ignoringParenImpCasts(equalsBoundNode("call"))))));
+
+  auto CapturedInLambda = hasDeclContext(cxxRecordDecl(
+      isLambda(),
+      hasParent(lambdaExpr(forCallable(equalsBoundNode("func")),
+                           anyOf(CapturedInCaptureList, CapturedInBody)))));
+
   auto ToParam = hasAnyParameter(parmVarDecl(equalsBoundNode("param")));
 
   auto ForwardCallMatcher = callExpr(
-      forCallable(equalsBoundNode("func")), argumentCountIs(1),
+      callExpr().bind("call"), argumentCountIs(1),
+      hasArgument(
+          0, declRefExpr(to(
+                 varDecl(optionally(equalsBoundNode("param"))).bind("var")))),
+      forCallable(anyOf(equalsBoundNode("func"), CapturedInLambda)),
       callee(unresolvedLookupExpr(hasAnyDeclaration(
           namedDecl(hasUnderlyingDecl(hasName("::std::forward")))))),
-      hasArgument(0, declRefExpr(to(equalsBoundNode("param"))).bind("ref")),
+
       unless(anyOf(hasAncestor(typeLoc()),
                    hasAncestor(expr(hasUnevaluatedContext())))));
 

clang-tools-extra/docs/ReleaseNotes.rst

@@ -295,6 +295,10 @@ Changes in existing checks
   coroutine functions and increase issue detection for cases involving type
   aliases with references.
 
+- Improved :doc:`cppcoreguidelines-missing-std-forward
+  <clang-tidy/checks/cppcoreguidelines/missing-std-forward>` check to
+  address false positives in the capture list and body of lambdas.
+
 - Improved :doc:`cppcoreguidelines-narrowing-conversions
   <clang-tidy/checks/cppcoreguidelines/narrowing-conversions>` check by
   extending the `IgnoreConversionFromTypes` option to include types without a

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/missing-std-forward.cpp

@@ -90,9 +90,9 @@ void lambda_value_capture(T&& t) {
 }
 
 template <class T>
-void lambda_value_reference(T&& t) {
-  // CHECK-MESSAGES: :[[@LINE-1]]:33: warning: forwarding reference parameter 't' is never forwarded inside the function body [cppcoreguidelines-missing-std-forward]
-  [&]() { T other = std::forward<T>(t); };
+void lambda_value_capture_copy(T&& t) {
+  // CHECK-MESSAGES: :[[@LINE-1]]:36: warning: forwarding reference parameter 't' is never forwarded inside the function body [cppcoreguidelines-missing-std-forward]
+  [&,t]() { T other = std::forward<T>(t); };
 }
 
 } // namespace positive_cases
@@ -147,4 +147,29 @@ class AClass {
   T data;
 };
 
+template <class T>
+void lambda_value_reference(T&& t) {
+  [&]() { T other = std::forward<T>(t); };
+}
+
+template<typename T>
+void lambda_value_reference_capture_list_ref_1(T&& t) {
+    [=, &t] { T other = std::forward<T>(t); };
+}
+
+template<typename T>
+void lambda_value_reference_capture_list_ref_2(T&& t) {
+    [&t] { T other = std::forward<T>(t); };
+}
+
+template<typename T>
+void lambda_value_reference_capture_list(T&& t) {
+    [t = std::forward<T>(t)] { t(); };
+}
+
+template <class T>
+void lambda_value_reference_auxiliary_var(T&& t) {
+  [&x = t]() { T other = std::forward<T>(x); };
+}
+
 } // namespace negative_cases