From 76a8f8cc71082c6195f7cfaf15d16612cf123b3d Mon Sep 17 00:00:00 2001
From: Alex Orlenko <zxteam@protonmail.com>
Date: Tue, 27 May 2025 01:31:54 +0100
Subject: [PATCH] Add `__type` to Error's userdata metatable. Close #585

---
 src/util/error.rs    |  6 +++++-
 src/util/userdata.rs | 10 +++++-----
 tests/luau.rs        | 11 +++++++++++
 3 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/src/util/error.rs b/src/util/error.rs
index 899522d..8629f11 100644
--- a/src/util/error.rs
+++ b/src/util/error.rs
@@ -349,7 +349,11 @@ pub(crate) unsafe fn init_error_registry(state: *mut ffi::lua_State) -> Result<(
         state,
         Some(|state| {
             ffi::lua_pushcfunction(state, error_tostring);
-            rawset_field(state, -2, "__tostring")
+            ffi::lua_setfield(state, -2, cstr!("__tostring"));
+
+            // This is mostly for Luau typeof() function
+            ffi::lua_pushstring(state, cstr!("error"));
+            ffi::lua_setfield(state, -2, cstr!("__type"));
         }),
     )?;
 
diff --git a/src/util/userdata.rs b/src/util/userdata.rs
index 2edbf0b..5e8d611 100644
--- a/src/util/userdata.rs
+++ b/src/util/userdata.rs
@@ -47,7 +47,7 @@ pub(crate) unsafe fn get_internal_metatable<T: TypeKey>(state: *mut ffi::lua_Sta
 // Uses 6 stack spaces and calls checkstack.
 pub(crate) unsafe fn init_internal_metatable<T: TypeKey>(
     state: *mut ffi::lua_State,
-    customize_fn: Option<fn(*mut ffi::lua_State) -> Result<()>>,
+    customize_fn: Option<fn(*mut ffi::lua_State)>,
 ) -> Result<()> {
     check_stack(state, 6)?;
 
@@ -62,11 +62,11 @@ pub(crate) unsafe fn init_internal_metatable<T: TypeKey>(
     ffi::lua_pushboolean(state, 0);
     rawset_field(state, -2, "__metatable")?;
 
-    if let Some(f) = customize_fn {
-        f(state)?;
-    }
-
     protect_lua!(state, 1, 0, |state| {
+        if let Some(f) = customize_fn {
+            f(state);
+        }
+
         ffi::lua_rawsetp(state, ffi::LUA_REGISTRYINDEX, T::type_key());
     })?;
 
diff --git a/tests/luau.rs b/tests/luau.rs
index 1b2cfc1..20fbee6 100644
--- a/tests/luau.rs
+++ b/tests/luau.rs
@@ -436,5 +436,16 @@ fn test_loadstring() -> Result<()> {
     Ok(())
 }
 
+#[test]
+fn test_typeof_error() -> Result<()> {
+    let lua = Lua::new();
+
+    let err = Error::runtime("just a test error");
+    let res = lua.load("return typeof(...)").call::<String>(err)?;
+    assert_eq!(res, "error");
+
+    Ok(())
+}
+
 #[path = "luau/require.rs"]
 mod require;