syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     /// the caller must specify what "flavor" of generator that they'd like to
context_before:     /// is agnostic to the type of generator that is returned (by-ref/by-move),
context_after:     /// create. Additionally, they must manually compute the upvars of the closure.