Post #2937853

I added `defer` to crescent (lang) last night. Seems like a straight-forward win in languages that support it. It was also a suprisingly easy feature to add. Args are evaluated at deferral time, calls are made LIFO when the enclosing scope closes. Very suspicious of how simple it is actually. The only things I could think of were compiler warnings on non-unit return types and errors on `@must_check` and `@allocates` (will probably rename these annotations)