syntax_data: {"ast_node_type":"other","tokens":[{"end":36,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// (end of a coroutine) states.
context_before:     /// `UNRESUMED` (beginning of a coroutine) and `RETURNED`/`POISONED`
context_after:     const RESERVED_VARIANTS: usize = 3;