[clang][dataflow] Handle CXXInheritedCtorInitExpr in ResultObjectVisitor. (#99616)

`CXXInheritedCtorInitExpr` is another of the node kinds that should be
considered an "original initializer". An assertion failure in
`assert(Children.size() == 1)` happens without this fix.

---------

Co-authored-by: martinboehme <[email protected]>

Author: Pask00

clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp

@@ -416,7 +416,7 @@ class ResultObjectVisitor : public AnalysisASTVisitor<ResultObjectVisitor> {
     // below them can initialize the same object (or part of it).
     if (isa<CXXConstructExpr>(E) || isa<CallExpr>(E) || isa<LambdaExpr>(E) ||
         isa<CXXDefaultArgExpr>(E) || isa<CXXStdInitializerListExpr>(E) ||
-        isa<AtomicExpr>(E) ||
+        isa<AtomicExpr>(E) || isa<CXXInheritedCtorInitExpr>(E) ||
         // We treat `BuiltinBitCastExpr` as an "original initializer" too as
         // it may not even be casting from a record type -- and even if it is,
         // the two objects are in general of unrelated type.

clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp

@@ -442,6 +442,55 @@ TEST_F(EnvironmentTest, CXXDefaultInitExprResultObjIsWrappedExprResultObj) {
             &Env.getResultObjectLocation(*DefaultInit->getExpr()));
 }
 
+// This test verifies the behavior of `getResultObjectLocation()` in
+// scenarios involving inherited constructors.
+// Since the specific AST node of interest `CXXConstructorDecl` is implicitly
+// generated, we cannot annotate any statements inside of it as we do in tests
+// within TransferTest. Thus, the only way to get the right `Environment` is by
+// explicitly initializing it as we do in tests within EnvironmentTest.
+// This is why this test is not inside TransferTest, where most of the tests for
+// `getResultObjectLocation()` are located.
+TEST_F(EnvironmentTest, ResultObjectLocationForInheritedCtorInitExpr) {
+  using namespace ast_matchers;
+
+  std::string Code = R"(
+    struct Base {
+      Base(int b) {}
+    };
+    struct Derived : Base {
+      using Base::Base;
+    };
+
+    Derived d = Derived(0);
+  )";
+
+  auto Unit =
+      tooling::buildASTFromCodeWithArgs(Code, {"-fsyntax-only", "-std=c++20"});
+  auto &Context = Unit->getASTContext();
+
+  ASSERT_EQ(Context.getDiagnostics().getClient()->getNumErrors(), 0U);
+
+  auto Results =
+      match(cxxConstructorDecl(
+                hasAnyConstructorInitializer(cxxCtorInitializer(
+                    withInitializer(expr().bind("inherited_ctor_init_expr")))))
+                .bind("ctor"),
+            Context);
+  const auto *Constructor = selectFirst<CXXConstructorDecl>("ctor", Results);
+  const auto *InheritedCtorInit = selectFirst<CXXInheritedCtorInitExpr>(
+      "inherited_ctor_init_expr", Results);
+
+  EXPECT_EQ(InheritedCtorInit->child_begin(), InheritedCtorInit->child_end());
+
+  Environment Env(DAContext, *Constructor);
+  Env.initialize();
+
+  RecordStorageLocation &Loc = Env.getResultObjectLocation(*InheritedCtorInit);
+  EXPECT_NE(&Loc, nullptr);
+
+  EXPECT_EQ(&Loc, Env.getThisPointeeStorageLocation());
+}
+
 TEST_F(EnvironmentTest, Stmt) {
   using namespace ast_matchers;