syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // whose `Sized`-ness relies on the hidden types of opaques defined by the
context_before:     // FIXME(#132279): @lcnr believes that we may want to support coroutines
context_after:     // parent function. In this case we'd have to be able to reveal only these