Calls the method, using the proc_name to call-through to Crystal.

If do_block is true, the generated Proc expression will use do ... end instead of { ... }. This allows embedding the code body inside a string conversion template, without the code block being interpreted as an environment variable (see also Template::Basic).

With crystal_object, for the override of a virtual method, the Proc takes the Crystal object as its first argument instead of capturing self, see CppToCrystalProc::CRYSTAL_OBJECT, and calls the override on it as an instance of typeof(self), the type the Proc is built in, which names a private type too. So the Proc captures nothing: a closure the C++ object holds would refer to the Crystal object, and the GC never finalizes an object reachable from itself through another, so neither would ever be collected.