Function arg_error_impl 

pub fn arg_error_impl(
    state: &mut LuaState,
    arg: i32,
    extramsg: &[u8],
) -> LuaError

Equivalent of C luaL_argerror: build an arg-type error with function name (from debug info) and caller source location. Handles method calls by producing “calling ‘f’ on bad self …” when arg==1 and namewhat==“method”.