syntax_data: {"ast_node_type":"function","tokens":[{"end":77,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:                 // fetch the fully liberated fn signature (that is, all bound
context_before:             rustc_hir::BodyOwnerKind::Fn | rustc_hir::BodyOwnerKind::Closure => {
context_after:                 // types/lifetimes replaced)