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a550087eee
The `luaL_testudata` and `luaL_checkudata` functions correctly treat the absence of a metatable for the type to check as the type not matching, so there is no need to have the type's metatable in memory until an object using it exists. Therefore we can defer the metatable's creation until the first time an object of that type is created. Saves some 4500 bytes of Lua heap RAM, at least if no such objects are created. The created metatables are shared between all scripts, so there is no increase in the total RAM usage if all objects are used. However, there is some increased risk of heap fragmentation and unexpected out-of-memory errors on rarely used code paths. It would be nice to construct the object in the new utility function, but it's not possible in C++ to take the address of a constructor. Instead passing in a lambda is ugly, hardly any more efficient, and screws up constructors which take parameters. Also optimizes by using the generated userdata creators where possible, and convincing the compiler to omit unnecessary checks.