How can I use the MaybeSend type?

[shanebishop]

I want to wrap calls to mlua::Lua::create_function so that I can have generic error handling for creation of different functions.

Here is what I tried:

fn create_function<'lua, A, R, F>(lua: &'lua Lua, name: &str, func: F) -> bool
where
    A: FromLuaMulti<'lua>,
    R: IntoLuaMulti<'lua>,
    F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
{
    let fun = lua.create_function(func);

    if let Ok(fun) = fun {
        lua.globals().set(name, fun);
        true
    } else {
        error!("Error creating function: {}", name);
        false
    }
}

However, I get this error:

error[E0405]: cannot find trait `MaybeSend` in this scope
   --> src/lib.rs:276:40
    |
276 |     F: Fn(&'lua Lua, A) -> Result<R> + MaybeSend + 'static,
    |                                        ^^^^^^^^^ not found in this scope

When I try adding use mlua::types::MaybeSend;, I get this error:

error[E0603]: module `types` is private
  --> src/lib.rs:19:11
   |
19 | use mlua::types::MaybeSend;
   |           ^^^^^  --------- trait `MaybeSend` is not publicly re-exported
   |           |
   |           private module

Is it possible for me to use the MaybeSend type? Or do I have no choice but to duplicate my error handling code for every call I make to mlua::Lua::create_function?

[khvzak]

MaybeSend trait depends on mlua send feature flag.
If it set then MaybeSend can be replaced with Send, otherwise just omitted.