Index: clangd/XRefs.cpp
===================================================================
--- clangd/XRefs.cpp
+++ clangd/XRefs.cpp
@@ -14,6 +14,16 @@
 using namespace llvm;
 namespace {
 
+bool IsDefinition(const Decl* D) {
+  if (const auto *TD = dyn_cast<TagDecl>(D))
+    return TD->isThisDeclarationADefinition();
+  else if (const auto *VD = dyn_cast<VarDecl>(D))
+    return VD->isThisDeclarationADefinition();
+  else if (const auto *FD = dyn_cast<FunctionDecl>(D))
+    return FD->isThisDeclarationADefinition();
+  return false;
+}
+
 /// Finds declarations locations that a given source location refers to.
 class DeclarationAndMacrosFinder : public index::IndexDataConsumer {
   std::vector<const Decl *> Decls;
@@ -50,8 +60,20 @@
                       ArrayRef<index::SymbolRelation> Relations, FileID FID,
                       unsigned Offset,
                       index::IndexDataConsumer::ASTNodeInfo ASTNode) override {
-    if (isSearchedLocation(FID, Offset))
-      Decls.push_back(D);
+    if (isSearchedLocation(FID, Offset)) {
+      // Find and add definition declarations (for GoToDefinition).
+      // We don't use parameter `D`, as Parameter `D` is the canonical
+      // declaration, which is the first declaration of a redeclarable
+      // declaration, and it could be a forward declaration.
+      auto Def = std::find_if(D->redecls_begin(), D->redecls_end(),
+                              [](const Decl *D) { return IsDefinition(D); });
+      if (Def != D->redecls_end()) {
+        Decls.push_back(*Def);
+      } else {
+        // Couldn't find a definition, fall back to use `D`.
+        Decls.push_back(D);
+      }
+    }
     return true;
   }
 
Index: unittests/clangd/XRefsTests.cpp
===================================================================
--- unittests/clangd/XRefsTests.cpp
+++ unittests/clangd/XRefsTests.cpp
@@ -203,6 +203,18 @@
         #define MACRO 2
         #undef macro
       )cpp",
+
+      R"cpp(// Forward class declaration
+        class Foo;
+        [[class Foo {}]];
+        F^oo* foo();
+      )cpp",
+
+      R"cpp(// Function declaration
+        void foo();
+        void g() { f^oo(); }
+        [[void foo() {}]]
+      )cpp",
   };
   for (const char *Test : Tests) {
     Annotations T(Test);