[clang][Index] Visit the default parameter arguements in libindex.

Summary:
We are missing the default parmeter arguments when IndexFunctionLocals
is true.

Fixes https://github.com/clangd/clangd/issues/285.

Reviewers: kadircet

Subscribers: kristof.beyls, ilya-biryukov, jkorous, arphaman, usaxena95, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D74610

clang-tools-extra/clangd/unittests/XRefsTests.cpp

@@ -943,6 +943,11 @@ TEST(FindReferences, WithinAST) {
           int x = [[MACRO]]([[MACRO]](1));
         }
       )cpp",
+
+      R"cpp(
+        int [[v^ar]] = 0;
+        void foo(int s = [[var]]);
+      )cpp",
   };
   for (const char *Test : Tests) {
     Annotations T(Test);

clang/lib/Index/IndexDecl.cpp

@@ -90,6 +90,12 @@ public:
                                  Parent->getLexicalDeclContext(),
                                  /*isBase=*/false, isIBType);
     IndexCtx.indexNestedNameSpecifierLoc(D->getQualifierLoc(), Parent);
+    auto IndexDefaultParmeterArgument = [&](const ParmVarDecl *Parm,
+                                            const NamedDecl *Parent) {
+      if (Parm->hasDefaultArg() && !Parm->hasUninstantiatedDefaultArg() &&
+          !Parm->hasUnparsedDefaultArg())
+        IndexCtx.indexBody(Parm->getDefaultArg(), Parent);
+    };
     if (IndexCtx.shouldIndexFunctionLocalSymbols()) {
       if (const ParmVarDecl *Parm = dyn_cast<ParmVarDecl>(D)) {
         auto *DC = Parm->getDeclContext();
@@ -106,7 +112,8 @@ public:
       } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
         if (IndexCtx.shouldIndexParametersInDeclarations() ||
             FD->isThisDeclarationADefinition()) {
-          for (auto PI : FD->parameters()) {
+          for (const auto *PI : FD->parameters()) {
+            IndexDefaultParmeterArgument(PI, D);
             IndexCtx.handleDecl(PI);
           }
         }
@@ -116,9 +123,7 @@ public:
       if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
         if (FD->isThisDeclarationADefinition()) {
           for (const auto *PV : FD->parameters()) {
-            if (PV->hasDefaultArg() && !PV->hasUninstantiatedDefaultArg() &&
-                !PV->hasUnparsedDefaultArg())
-              IndexCtx.indexBody(PV->getDefaultArg(), D);
+            IndexDefaultParmeterArgument(PV, D);
           }
         }
       }

clang/unittests/Index/IndexTests.cpp

@@ -319,6 +319,21 @@ TEST(IndexTest, InjecatedNameClass) {
                                          WrittenAt(Position(4, 14)))));
 }
 
+TEST(IndexTest, VisitDefaultArgs) {
+  std::string Code = R"cpp(
+    int var = 0;
+    void f(int s = var) {}
+  )cpp";
+  auto Index = std::make_shared<Indexer>();
+  IndexingOptions Opts;
+  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)))));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang