[clang][dataflow] fix assert in Environment::getResultObjectLocation (#79608)

When calling `Environment::getResultObjectLocation` with a
CXXOperatorCallExpr that is a prvalue, we just hit an assert because no
record was ever created.

---------

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

Author: paulsemel

clang/lib/Analysis/FlowSensitive/Transfer.cpp

@@ -536,7 +536,13 @@ class TransferVisitor : public ConstStmtVisitor<TransferVisitor> {
 
       copyRecord(*LocSrc, *LocDst, Env);
       Env.setStorageLocation(*S, *LocDst);
+      return;
     }
+
+    // CXXOperatorCallExpr can be prvalues. Call `VisitCallExpr`() to create
+    // a `RecordValue` for them so that `Environment::getResultObjectLocation()`
+    // can return a value.
+    VisitCallExpr(S);
   }
 
   void VisitCXXFunctionalCastExpr(const CXXFunctionalCastExpr *S) {

clang/unittests/Analysis/FlowSensitive/TransferTest.cpp

@@ -2735,6 +2735,39 @@ TEST(TransferTest, ResultObjectLocationForDefaultInitExpr) {
       });
 }
 
+// This test ensures that CXXOperatorCallExpr returning prvalues are correctly
+// handled by the transfer functions, especially that `getResultObjectLocation`
+// correctly returns a storage location for those.
+TEST(TransferTest, ResultObjectLocationForCXXOperatorCallExpr) {
+  std::string Code = R"(
+    struct A {
+      A operator+(int);
+    };
+
+    void target() {
+      A a;
+      a + 3;
+      (void)0; // [[p]]
+    }
+  )";
+  using ast_matchers::cxxOperatorCallExpr;
+  using ast_matchers::match;
+  using ast_matchers::selectFirst;
+  using ast_matchers::traverse;
+  runDataflow(
+      Code,
+      [](const llvm::StringMap<DataflowAnalysisState<NoopLattice>> &Results,
+         ASTContext &ASTCtx) {
+        const Environment &Env = getEnvironmentAtAnnotation(Results, "p");
+
+        auto *CallExpr = selectFirst<CXXOperatorCallExpr>(
+            "call_expr",
+            match(cxxOperatorCallExpr().bind("call_expr"), ASTCtx));
+
+        EXPECT_NE(&Env.getResultObjectLocation(*CallExpr), nullptr);
+      });
+}
+
 TEST(TransferTest, StaticCast) {
   std::string Code = R"(
     void target(int Foo) {