Remove SubtypeId from AnyUserData and instead add Value::Other variant that will cover any unknown types (eg. LuaJIT CData)

src/scope.rs

@@ -6,7 +6,7 @@ use std::os::raw::c_void;
 use crate::error::{Error, Result};
 use crate::function::Function;
 use crate::state::{Lua, LuaGuard, RawLua};
-use crate::types::{Callback, CallbackUpvalue, ScopedCallback, SubtypeId, ValueRef};
+use crate::types::{Callback, CallbackUpvalue, ScopedCallback, ValueRef};
 use crate::userdata::{AnyUserData, UserData, UserDataRegistry, UserDataStorage};
 use crate::util::{self, assert_stack, check_stack, get_userdata, take_userdata, StackGuard};
 use crate::value::{FromLuaMulti, IntoLuaMulti};
@@ -186,7 +186,7 @@ impl<'scope, 'env: 'scope> Scope<'scope, 'env> {
             std::ptr::write(ud_ptr, UserDataStorage::new_scoped(data));
             ffi::lua_setmetatable(state, -2);
 
-            let ud = AnyUserData(self.lua.pop_ref(), SubtypeId::None);
+            let ud = AnyUserData(self.lua.pop_ref());
 
             let destructor: DestructorCallback = Box::new(|rawlua, vref| {
                 let state = rawlua.state();

src/serde/de.rs

@@ -150,7 +150,8 @@ impl<'de> serde::Deserializer<'de> for Deserializer {
             | Value::Thread(_)
             | Value::UserData(_)
             | Value::LightUserData(_)
-            | Value::Error(_) => {
+            | Value::Error(_)
+            | Value::Other(_) => {
                 if self.options.deny_unsupported_types {
                     let msg = format!("unsupported value type `{}`", self.value.type_name());
                     Err(de::Error::custom(msg))

src/state/raw.rs

@@ -18,7 +18,7 @@ use crate::table::Table;
 use crate::thread::Thread;
 use crate::types::{
     AppDataRef, AppDataRefMut, Callback, CallbackUpvalue, DestructedUserdata, Integer, LightUserData,
-    MaybeSend, ReentrantMutex, RegistryKey, SubtypeId, ValueRef, XRc,
+    MaybeSend, ReentrantMutex, RegistryKey, ValueRef, XRc,
 };
 use crate::userdata::{AnyUserData, MetaMethod, UserData, UserDataRegistry, UserDataStorage};
 use crate::util::{
@@ -560,6 +560,7 @@ impl RawLua {
                 let protect = !self.unlikely_memory_error();
                 push_internal_userdata(state, WrappedFailure::Error(*err.clone()), protect)?;
             }
+            Value::Other(vref) => self.push_ref(vref),
         }
         Ok(())
     }
@@ -644,7 +645,7 @@ impl RawLua {
                     }
                     _ => {
                         ffi::lua_xpush(state, self.ref_thread(), idx);
-                        Value::UserData(AnyUserData(self.pop_ref_thread(), SubtypeId::None))
+                        Value::UserData(AnyUserData(self.pop_ref_thread()))
                     }
                 }
             }
@@ -661,14 +662,10 @@ impl RawLua {
                 Value::Buffer(crate::Buffer(self.pop_ref_thread()))
             }
 
-            #[cfg(feature = "luajit")]
-            ffi::LUA_TCDATA => {
-                // CData is represented as a userdata type
+            _ => {
                 ffi::lua_xpush(state, self.ref_thread(), idx);
-                Value::UserData(AnyUserData(self.pop_ref_thread(), SubtypeId::CData))
+                Value::Other(self.pop_ref_thread())
             }
-
-            _ => mlua_panic!("unexpected value type on stack"),
         }
     }
 
@@ -806,7 +803,7 @@ impl RawLua {
             ffi::lua_setuservalue(state, -2);
         }
 
-        Ok(AnyUserData(self.pop_ref(), SubtypeId::None))
+        Ok(AnyUserData(self.pop_ref()))
     }
 
     pub(crate) unsafe fn create_userdata_metatable<T>(

src/types.rs

@@ -28,14 +28,6 @@ pub type Integer = ffi::lua_Integer;
 /// Type of Lua floating point numbers.
 pub type Number = ffi::lua_Number;
 
-// Represents different subtypes wrapped in AnyUserData
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub(crate) enum SubtypeId {
-    None,
-    #[cfg(feature = "luajit")]
-    CData,
-}
-
 /// A "light" userdata value. Equivalent to an unmanaged raw pointer.
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub struct LightUserData(pub *mut c_void);

src/userdata.rs

@@ -19,7 +19,7 @@ use crate::function::Function;
 use crate::state::Lua;
 use crate::string::String;
 use crate::table::{Table, TablePairs};
-use crate::types::{MaybeSend, SubtypeId, ValueRef};
+use crate::types::{MaybeSend, ValueRef};
 use crate::util::{check_stack, get_userdata, take_userdata, StackGuard};
 use crate::value::{FromLua, FromLuaMulti, IntoLua, IntoLuaMulti, Value};
 
@@ -643,7 +643,7 @@ pub trait UserData: Sized {
 /// [`is`]: crate::AnyUserData::is
 /// [`borrow`]: crate::AnyUserData::borrow
 #[derive(Clone, Debug)]
-pub struct AnyUserData(pub(crate) ValueRef, pub(crate) SubtypeId);
+pub struct AnyUserData(pub(crate) ValueRef);
 
 impl AnyUserData {
     /// Checks whether the type of this userdata is `T`.
@@ -935,12 +935,6 @@ impl AnyUserData {
 
     /// Returns a type name of this `UserData` (from a metatable field).
     pub(crate) fn type_name(&self) -> Result<Option<StdString>> {
-        match self.1 {
-            SubtypeId::None => {}
-            #[cfg(feature = "luajit")]
-            SubtypeId::CData => return Ok(Some("cdata".to_owned())),
-        }
-
         let lua = self.0.lua.lock();
         let state = lua.state();
         unsafe {

src/userdata/object.rs

@@ -88,6 +88,6 @@ impl ObjectLike for AnyUserData {
 
     #[inline]
     fn to_string(&self) -> Result<StdString> {
-        Value::UserData(AnyUserData(self.0.copy(), self.1)).to_string()
+        Value::UserData(AnyUserData(self.0.copy())).to_string()
     }
 }

src/util/mod.rs

@@ -275,9 +275,10 @@ pub(crate) unsafe fn to_string(state: *mut ffi::lua_State, index: c_int) -> Stri
         ffi::LUA_TTHREAD => format!("<thread {:?}>", ffi::lua_topointer(state, index)),
         #[cfg(feature = "luau")]
         ffi::LUA_TBUFFER => format!("<buffer {:?}>", ffi::lua_topointer(state, index)),
-        #[cfg(feature = "luajit")]
-        ffi::LUA_TCDATA => format!("<cdata {:?}>", ffi::lua_topointer(state, index)),
-        _ => "<unknown>".to_string(),
+        type_id => {
+            let type_name = CStr::from_ptr(ffi::lua_typename(state, type_id)).to_string_lossy();
+            format!("<{type_name} {:?}>", ffi::lua_topointer(state, index))
+        }
     }
 }
 

src/value.rs

@@ -14,7 +14,7 @@ use crate::state::{Lua, RawLua};
 use crate::string::{BorrowedStr, String};
 use crate::table::Table;
 use crate::thread::Thread;
-use crate::types::{Integer, LightUserData, Number, SubtypeId, ValueRef};
+use crate::types::{Integer, LightUserData, Number, ValueRef};
 use crate::userdata::AnyUserData;
 use crate::util::{check_stack, StackGuard};
 
@@ -28,7 +28,7 @@ use {
 
 /// A dynamically typed Lua value.
 ///
-/// The `String`, `Table`, `Function`, `Thread`, and `UserData` variants contain handle types
+/// The non-primitive variants (eg. string/table/function/thread/userdata) contain handle types
 /// into the internal Lua state. It is a logic error to mix handle types between separate
 /// `Lua` instances, and doing so will result in a panic.
 #[derive(Clone)]
@@ -69,6 +69,9 @@ pub enum Value {
     Buffer(crate::Buffer),
     /// `Error` is a special builtin userdata type. When received from Lua it is implicitly cloned.
     Error(Box<Error>),
+    /// Any other value not known to mlua (eg. LuaJIT CData).
+    #[allow(private_interfaces)]
+    Other(ValueRef),
 }
 
 pub use self::Value::Nil;
@@ -93,12 +96,11 @@ impl Value {
             Value::Table(_) => "table",
             Value::Function(_) => "function",
             Value::Thread(_) => "thread",
-            Value::UserData(AnyUserData(_, SubtypeId::None)) => "userdata",
-            #[cfg(feature = "luajit")]
-            Value::UserData(AnyUserData(_, SubtypeId::CData)) => "cdata",
+            Value::UserData(_) => "userdata",
             #[cfg(feature = "luau")]
             Value::Buffer(_) => "buffer",
             Value::Error(_) => "error",
+            Value::Other(_) => "other",
         }
     }
 
@@ -173,7 +175,8 @@ impl Value {
             Value::Table(Table(vref))
             | Value::Function(Function(vref))
             | Value::Thread(Thread(vref, ..))
-            | Value::UserData(AnyUserData(vref, ..)) => unsafe { invoke_to_string(vref) },
+            | Value::UserData(AnyUserData(vref))
+            | Value::Other(vref) => unsafe { invoke_to_string(vref) },
             #[cfg(feature = "luau")]
             Value::Buffer(crate::Buffer(vref)) => unsafe { invoke_to_string(vref) },
             Value::Error(err) => Ok(err.to_string()),
@@ -448,17 +451,6 @@ impl Value {
         self.as_buffer().is_some()
     }
 
-    /// Returns `true` if the value is a CData wrapped in [`AnyUserData`].
-    #[cfg(any(feature = "luajit", doc))]
-    #[cfg_attr(docsrs, doc(cfg(feature = "luajit")))]
-    #[doc(hidden)]
-    #[inline]
-    pub fn is_cdata(&self) -> bool {
-        self.as_userdata()
-            .map(|ud| ud.1 == SubtypeId::CData)
-            .unwrap_or_default()
-    }
-
     /// Wrap reference to this Value into [`SerializableValue`].
     ///
     /// This allows customizing serialization behavior using serde.
@@ -548,6 +540,7 @@ impl Value {
             buf @ Value::Buffer(_) => write!(fmt, "buffer: {:?}", buf.to_pointer()),
             Value::Error(e) if recursive => write!(fmt, "{e:?}"),
             Value::Error(_) => write!(fmt, "error"),
+            Value::Other(v) => write!(fmt, "other: {:?}", v.to_pointer()),
         }
     }
 }
@@ -574,6 +567,7 @@ impl fmt::Debug for Value {
             #[cfg(feature = "luau")]
             Value::Buffer(buf) => write!(fmt, "{buf:?}"),
             Value::Error(e) => write!(fmt, "Error({e:?})"),
+            Value::Other(v) => write!(fmt, "Other({v:?})"),
         }
     }
 }
@@ -711,7 +705,8 @@ impl<'a> Serialize for SerializableValue<'a> {
             | Value::Thread(_)
             | Value::UserData(_)
             | Value::LightUserData(_)
-            | Value::Error(_) => {
+            | Value::Error(_)
+            | Value::Other(_) => {
                 if self.options.deny_unsupported_types {
                     let msg = format!("cannot serialize <{}>", self.value.type_name());
                     Err(ser::Error::custom(msg))

tests/tests.rs

@@ -1256,8 +1256,7 @@ fn test_luajit_cdata() -> Result<()> {
     "#,
         )
         .eval::<Value>()?;
-    assert!(cdata.is_userdata() && cdata.is_cdata());
-    assert_eq!(cdata.type_name(), "cdata");
+    assert_eq!(cdata.type_name(), "other");
     assert!(cdata.to_string()?.starts_with("cdata<void *>:"));
 
     Ok(())