[clang][dataflow] Add support for comma binary operator

[sgatev]

Summary

Add support for comma binary operator.

[ymandel]

Thanks!

clang/lib/Analysis/FlowSensitive/Transfer.cpp

void VisitBinaryOperator(const BinaryOperator *S) {
     case BO_EQ: {
       auto &LHSEqRHSValue = evaluateBooleanEquality(*LHS, *RHS, Env);
       auto &Loc = Env.createStorageLocation(*S);
       Env.setStorageLocation(*S, Loc);
       Env.setValue(Loc, S->getOpcode() == BO_EQ ? LHSEqRHSValue
                                                 : Env.makeNot(LHSEqRHSValue));
       break;
     }
+    case BO_Comma: {
+      if (auto *Loc = Env.getStorageLocation(*RHS, SkipPast::None))
+        Env.setStorageLocation(*S, *Loc);
+      break;
+    }
     default:
       break;
     }
   }
 
   void VisitDeclRefExpr(const DeclRefExpr *S) {
     assert(S->getDecl() != nullptr);
     auto *DeclLoc = Env.getStorageLocation(*S->getDecl(), SkipPast::None);

clang/unittests/Analysis/FlowSensitive/TransferTest.cpp

runDataflow(
         const StorageLocation *BoundBarLoc =
             Env.getStorageLocation(*BoundBarDecl, SkipPast::Reference);
         EXPECT_NE(BoundBarLoc, BarRefLoc);
 
         EXPECT_EQ(Env.getValue(*BoundFooDecl, SkipPast::Reference), QuxVal);
       });
 }
 
+TEST_F(TransferTest, BinaryOperatorComma) {
+  std::string Code = R"(
+    void target(int Foo, int Bar) {
+      int &Baz = (Foo, Bar);
+      // [[p]]
+    }
+  )";
+  runDataflow(Code,
+              [](llvm::ArrayRef<
+                     std::pair<std::string, DataflowAnalysisState<NoopLattice>>>
+                     Results,
+                 ASTContext &ASTCtx) {
+                ASSERT_THAT(Results, ElementsAre(Pair("p", _)));
+                const Environment &Env = Results[0].second.Env;
+
+                const ValueDecl *BarDecl = findValueDecl(ASTCtx, "Bar");
+                ASSERT_THAT(BarDecl, NotNull());
+
+                const ValueDecl *BazDecl = findValueDecl(ASTCtx, "Baz");
+                ASSERT_THAT(BazDecl, NotNull());
+
+                const StorageLocation *BarLoc =
+                    Env.getStorageLocation(*BarDecl, SkipPast::Reference);
+                ASSERT_THAT(BarLoc, NotNull());
+
+                const StorageLocation *BazLoc =
+                    Env.getStorageLocation(*BazDecl, SkipPast::Reference);
+                EXPECT_EQ(BazLoc, BarLoc);
+              });
+}
+
 } // namespace