syntax_data: {"ast_node_type":"other","tokens":[{"end":86,"kind":"keyword","start":0,"text":"\"`FnOnce`"}]}
source_snippet:                     "`FnOnce` coroutine-closures return coroutines that capture from \
context_before:                     parent_capture.is_by_ref() || coroutine_kind != ty::ClosureKind::FnOnce,
context_after:                         their body; it will always result in a borrowck error!"