[clang][index] Fix processing of CompoundAssignOperator at setting up reference roles (#69370)

Without this patch in expressions like `foo += 1` reference `foo` has no
read and write roles.

This happens because `CompoundAssignOperator` is also a
`BinaryOperator`, thus handling `CompoindAssignOperator` in `else`
branch is a dead code.

Author: ArcsinX

clang/lib/Index/IndexBody.cpp

@@ -77,9 +77,15 @@ class BodyIndexer : public RecursiveASTVisitor<BodyIndexer> {
     const Stmt *Parent = *It;
 
     if (auto BO = dyn_cast<BinaryOperator>(Parent)) {
-      if (BO->getOpcode() == BO_Assign && BO->getLHS()->IgnoreParenCasts() == E)
-        Roles |= (unsigned)SymbolRole::Write;
-
+      if (BO->getOpcode() == BO_Assign) {
+        if (BO->getLHS()->IgnoreParenCasts() == E)
+          Roles |= (unsigned)SymbolRole::Write;
+      } else if (auto CA = dyn_cast<CompoundAssignOperator>(Parent)) {
+        if (CA->getLHS()->IgnoreParenCasts() == E) {
+          Roles |= (unsigned)SymbolRole::Read;
+          Roles |= (unsigned)SymbolRole::Write;
+        }
+      }
     } else if (auto UO = dyn_cast<UnaryOperator>(Parent)) {
       if (UO->isIncrementDecrementOp()) {
         Roles |= (unsigned)SymbolRole::Read;
@@ -88,12 +94,6 @@ class BodyIndexer : public RecursiveASTVisitor<BodyIndexer> {
         Roles |= (unsigned)SymbolRole::AddressOf;
       }
 
-    } else if (auto CA = dyn_cast<CompoundAssignOperator>(Parent)) {
-      if (CA->getLHS()->IgnoreParenCasts() == E) {
-        Roles |= (unsigned)SymbolRole::Read;
-        Roles |= (unsigned)SymbolRole::Write;
-      }
-
     } else if (auto CE = dyn_cast<CallExpr>(Parent)) {
       if (CE->getCallee()->IgnoreParenCasts() == E) {
         addCallRole(Roles, Relations);

clang/unittests/Index/IndexTests.cpp

@@ -428,6 +428,31 @@ TEST(IndexTest, NonTypeTemplateParameter) {
                              WrittenAt(Position(3, 15)))));
 }
 
+TEST(IndexTest, ReadWriteRoles) {
+  std::string Code = R"cpp(
+    int main() {
+      int foo = 0;
+      foo = 2;
+      foo += 1;
+      int bar = foo;
+  }
+  )cpp";
+  auto Index = std::make_shared<Indexer>();
+  IndexingOptions Opts;
+  Opts.IndexFunctionLocals = true;
+  tooling::runToolOnCode(std::make_unique<IndexAction>(Index, Opts), Code);
+  EXPECT_THAT(
+      Index->Symbols,
+      AllOf(Contains(AllOf(QName("foo"), HasRole(SymbolRole::Write),
+                           WrittenAt(Position(4, 7)))),
+            Contains(AllOf(QName("foo"),
+                           HasRole(static_cast<unsigned>(SymbolRole::Read) |
+                                   static_cast<unsigned>(SymbolRole::Write)),
+                           WrittenAt(Position(5, 7)))),
+            Contains(AllOf(QName("foo"), HasRole(SymbolRole::Read),
+                           WrittenAt(Position(6, 17))))));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang