[clang][index] index the missing LabelDecl in libindex.

[hokein]

add a clangd xref test.

[kadircet]

we should also be handling LabelDecls in clang/lib/Index/IndexDecl.cpp

clang/lib/Index/IndexBody.cpp

145

this should propagate the result from handleReference, i.e return IndexCtx.handleRefer....

146

s/unsigned/SymbolRoleSet

154

the two comments above also applies to this one.

clang/unittests/Index/IndexTests.cpp

355

nit: just Not(Contains(QName("label"))

[kadircet]

clang/lib/Index/IndexBody.cpp

152

argh, looks like RecursiveASTVisitor doesn't traverse LabelDecl inside the LabelStmt. So feel free to fix that in RAV or call IndexCtx.handleDecl(LabelDecl) in here with a fixme. (hopefully nothing much should break with the former though)

clang/unittests/Index/IndexTests.cpp

349

i believe we should see the "definition/declaration" of label rather than a reference

clang/lib/Index/IndexBody.cpp

public:
 
   bool VisitDeclRefExpr(DeclRefExpr *E) {
     SmallVector<SymbolRelation, 4> Relations;
     SymbolRoleSet Roles = getRolesForRef(E, Relations);
     return IndexCtx.handleReference(E->getDecl(), E->getLocation(),
                                     Parent, ParentDC, Roles, Relations, E);
   }
 
+  bool VisitGotoStmt(GotoStmt *Goto) {
+    if (auto *LabelDecl = Goto->getLabel())
+      IndexCtx.handleReference(LabelDecl, Goto->getLabelLoc(), Parent, ParentDC,
+                               static_cast<unsigned>(SymbolRole::Reference));
+    return true;
+  }
+
+  bool VisitLabelStmt(LabelStmt *Label) {
+    if (auto *LabelDecl = Label->getDecl())
+      IndexCtx.handleReference(LabelDecl, Label->getIdentLoc(), Parent,
+                               ParentDC,
+                               static_cast<unsigned>(SymbolRole::Reference));
+    return true;
+  }
+
   bool VisitMemberExpr(MemberExpr *E) {
     SourceLocation Loc = E->getMemberLoc();
     if (Loc.isInvalid())
       Loc = E->getBeginLoc();
     SmallVector<SymbolRelation, 4> Relations;
     SymbolRoleSet Roles = getRolesForRef(E, Relations);
     return IndexCtx.handleReference(E->getMemberDecl(), Loc,
                                     Parent, ParentDC, Roles, Relations, E);

clang/unittests/Index/IndexTests.cpp

TEST(IndexTest, VisitDefaultArgs) {
   Opts.IndexFunctionLocals = true;
   Opts.IndexParametersInDeclarations = true;
   tooling::runToolOnCode(std::make_unique<IndexAction>(Index, Opts), Code);
   EXPECT_THAT(Index->Symbols,
               Contains(AllOf(QName("var"), HasRole(SymbolRole::Reference),
                              WrittenAt(Position(3, 20)))));
 }
 
+TEST(IndexTest, LabelDecl) {
+  std::string Code = R"cpp(
+    void foo() {
+    label:
+      return;
+    }
+  )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,
+              Contains(AllOf(QName("label"), HasRole(SymbolRole::Reference),
+                             WrittenAt(Position(3, 5)))));
+  Index->Symbols.clear();
+  Opts.IndexFunctionLocals = false;
+  tooling::runToolOnCode(std::make_unique<IndexAction>(Index, Opts), Code);
+  EXPECT_THAT(Index->Symbols,
+              Not(Contains(AllOf(QName("label"), HasRole(SymbolRole::Reference),
+                                 WrittenAt(Position(3, 5))))));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang