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Fix non userdata const reference overloads #270

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Merged
kunitoki merged 1 commit into from
Sep 8, 2026
Merged

Fix non userdata const reference overloads #270

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12 changes: 8 additions & 4 deletions Distribution/LuaBridge/LuaBridge.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6376,7 +6376,8 @@ struct StackOpSelector<T*, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -6391,7 +6392,8 @@ struct StackOpSelector<const T*, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -6403,7 +6405,8 @@ struct StackOpSelector<T&, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -6415,7 +6418,8 @@ struct StackOpSelector<const T&, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

}
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12 changes: 8 additions & 4 deletions Source/LuaBridge/detail/Stack.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1518,7 +1518,8 @@ struct StackOpSelector<T*, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -1533,7 +1534,8 @@ struct StackOpSelector<const T*, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -1545,7 +1547,8 @@ struct StackOpSelector<T&, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

template <class T>
Expand All @@ -1557,7 +1560,8 @@ struct StackOpSelector<const T&, false>

static ReturnType get(lua_State* L, int index) { return Stack<T>::get(L, index); }

static bool isInstance(lua_State* L, int index) { return Stack<T>::isInstance(L, index); }
template <class U = T>
static bool isInstance(lua_State* L, int index) { return Stack<U>::isInstance(L, index); }
};

} // namespace detail
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45 changes: 45 additions & 0 deletions Tests/Source/OverloadTests.cpp
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Expand Up @@ -549,6 +549,51 @@ TEST_F(OverloadTests, OverloadOperatorClass)
EXPECT_EQ(6, result2.value);
}

TEST_F(OverloadTests, ConstReferenceToNonUserdataParameters)
{
// Registering an overload set whose parameters are references to
// non-userdata types instantiates Stack<const T&>::isInstance, which used to
// be a compile error. Arity alone selects the overload here, so the runtime
// expectations stay unambiguous.
struct X
{
int sum(const int& a) const { return a; }
int sum(const int& a, const int& b) const { return a + b; }
};

luabridge::getGlobalNamespace(L)
.beginClass<X>("X")
.addConstructor<void()>()
.addFunction("sum",
luabridge::constOverload<const int&>(&X::sum),
luabridge::constOverload<const int&, const int&>(&X::sum))
.endClass();

runLua("x = X(); result = x:sum(3)");
EXPECT_EQ(3, result<int>());

runLua("x = X(); result = x:sum(3, 4)");
EXPECT_EQ(7, result<int>());
}

TEST_F(OverloadTests, ConstReferenceToStringParameters)
{
luabridge::getGlobalNamespace(L)
.addFunction("test",
[](const std::string& s) -> int {
return static_cast<int>(s.size());
},
[](const std::string& s, const int& factor) -> int {
return static_cast<int>(s.size()) * factor;
});

runLua("result = test ('abcd')");
EXPECT_EQ(4, result<int>());

runLua("result = test ('abcd', 3)");
EXPECT_EQ(12, result<int>());
}

TEST_F(OverloadTests, LuaCFunctionFallback)
{
struct X
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47 changes: 47 additions & 0 deletions Tests/Source/StackTests.cpp
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Expand Up @@ -32,6 +32,53 @@ TEST_F(StackTests, VoidStackOverflow)
ASSERT_TRUE(luabridge::Stack<void>::push(L));
}

TEST_F(StackTests, ReferenceAndPointerToNonUserdataTypes)
{
// Stack<T&>, Stack<const T&>, Stack<T*> and Stack<const T*> all forward to
// `Helper::template isInstance<T>(...)`, which requires the selected
// StackOpSelector to declare isInstance as a template. The non-userdata
// specialisations declared it as a plain static function, so instantiating
// isInstance for a reference or pointer to any non-userdata type was a hard
// compile error ("'isInstance' following the 'template' keyword does not
// refer to a template"). That made luabridge::overload<const T&>(...)
// unusable for int, double, std::string and every other non-userdata type.
{
ASSERT_TRUE(luabridge::push(L, 42));

EXPECT_TRUE(luabridge::isInstance<int&>(L, -1));
EXPECT_TRUE(luabridge::isInstance<const int&>(L, -1));
EXPECT_TRUE(luabridge::isInstance<int*>(L, -1));
EXPECT_TRUE(luabridge::isInstance<const int*>(L, -1));

EXPECT_TRUE(luabridge::isInstance<double&>(L, -1));
EXPECT_TRUE(luabridge::isInstance<const double&>(L, -1));

lua_pop(L, 1);
}

{
ASSERT_TRUE(luabridge::push(L, std::string("abc")));

EXPECT_TRUE(luabridge::isInstance<std::string&>(L, -1));
EXPECT_TRUE(luabridge::isInstance<const std::string&>(L, -1));

EXPECT_FALSE(luabridge::isInstance<int&>(L, -1));
EXPECT_FALSE(luabridge::isInstance<const int&>(L, -1));

// The userdata specialisations reach isInstance through the same path
// and must keep working.
EXPECT_FALSE(luabridge::isInstance<Unregistered&>(L, -1));
EXPECT_FALSE(luabridge::isInstance<const Unregistered&>(L, -1));

// An explicit U is forwarded rather than silently replaced by T, which
// mirrors how the userdata selectors forward Userdata::isInstance<U>.
EXPECT_TRUE(
(luabridge::detail::StackOpSelector<const int&, false>::isInstance<std::string>(L, -1)));

lua_pop(L, 1);
}
}

TEST_F(StackTests, NullptrType)
{
{
Expand Down
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