syntax_data: {"ast_node_type":"other","tokens":[{"end":20,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // opaques here.
context_before:     // parent function. In this case we'd have to be able to reveal only these
context_after:     let infcx = tcx.infer_ctxt().ignoring_regions().build(TypingMode::non_body_analysis());