check error of calling member function by wrong syntax: obj.func()

include/peacalm/luaw.h

@@ -4336,7 +4336,11 @@ struct luaw::registrar<Return (Class::*)(Args...)> {
   static void register_member_function(luaw&            l,
                                        const char*      fname,
                                        MemberFunction&& mf) {
-    auto f = [=](ObjectType o, Args... args) -> Return {
+    auto f = [mf, &l](ObjectType o, Args... args) -> Return {
+      if (!o) {
+        luaL_error(l.L(), "Calling member function by null pointer of object");
+        return Return();
+      }
       PEACALM_LUAW_ASSERT(o);
       return mf(*o, std::move(args)...);
     };

test/unit_test/register_member.cpp

@@ -27,6 +27,12 @@ struct Obj {
   int cv_geti() const volatile { return i; }
 
   int plus() { return ++i; }
+  int plusby(int d) {
+    i += d;
+    return i;
+  }
+
+  void reset() { i = 0; }
 
   int overloaded_f() { return i + 1000; }
   int overloaded_f() const { return i + 2000; }
@@ -346,6 +352,46 @@ TEST(register_member, member_functions) {
   EXPECT_EQ(l.gettop(), 0);
 }
 
+TEST(register_member, member_functions_by_wrong_syntax_call) {
+  luaw l;
+
+  l.register_member("i", &Obj::i);
+  l.register_member("plus", &Obj::plus);
+  l.register_member("plusby", &Obj::plusby);
+  l.register_member("reset", &Obj::reset);
+
+  Obj o;
+  l.set("o", &o);
+
+  int ret_code = l.dostring("o.plus()");
+  EXPECT_NE(ret_code, LUA_OK);
+  l.log_error_out();
+  EXPECT_EQ(o.i, 1);
+
+  bool failed;
+  int  reti = l.eval_int("return o.plus()", -1, false, &failed);
+  EXPECT_EQ(reti, -1);
+  EXPECT_TRUE(failed);
+
+  ret_code = l.dostring("o:plus()");
+  EXPECT_EQ(ret_code, LUA_OK);
+  EXPECT_EQ(o.i, 2);
+
+  ret_code = l.dostring("o:reset()");
+  EXPECT_EQ(ret_code, LUA_OK);
+  EXPECT_EQ(o.i, 0);
+
+  ret_code = l.dostring("o.plusby(3)");
+  EXPECT_NE(ret_code, LUA_OK);
+  l.log_error_out();
+  EXPECT_EQ(o.i, 0);
+
+  EXPECT_EQ(l.eval_int("return o.plusby(o, 5)"), 5);
+  EXPECT_EQ(l.eval_int("return o:plusby(5)"), 10);
+
+  EXPECT_EQ(l.gettop(), 0);
+}
+
 TEST(register_member, result_status_of_get) {
   luaw l;
   l.set("o", Obj{});