Should `ToLua` take `self` by reference.

[kaikalii]

Basically every implementation of ToLua is not actually going to consume the value, yet ToLua::to_lua (or 0.9 IntoLua::into_lua) takes self by value. The only time I can think when you might need to move out of self when converting to a mlua::Value is when self contains a lua object in the first place, in which case you can just cheaply clone it.

I am finding I sometimes have to clone more expensive things to convert them to Lua values when that shouldn't be necessary.

Should the method take &self? Maybe only require Self: ?Sized?

The only downside I can see is that it would be a breaking change, and a minor one to patch at that.

If this is agreeable, I'd be happy to implement it.

[khvzak]

The only time I can think when you might need to move out of self when converting to a mlua::Value is when self contains a lua object in the first place, in which case you can just cheaply clone it.

There is one more reason actually:

impl<'lua, T: UserData + MaybeSend + 'static> IntoLua<'lua> for T {
    fn into_lua(self, lua: &'lua Lua) -> Result<Value<'lua>> {
        Ok(Value::UserData(lua.create_userdata(self)?))
    }
}

I was thinking about taking self by reference and keeping the trait name ToLua, but seems having the ability to move T into lua is more valuable.

I am finding I sometimes have to clone more expensive things to convert them to Lua values when that shouldn't be necessary.

What data structures you use? IntoLua is implemented for few reference objects like &[], &str. Maybe adding few more implementations would help?

[kaikalii]

Ah I see. I didn't realize &[] implemented IntoLua. I think it would be good if &HashMap and &BTreeMap implemented it (and maybe the *Sets too).