syntax_data: {"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             // `Err(Unimplemented)` to `Ok(None)`. This helps us avoid
context_before:             // If there's an error type, 'downgrade' our result from
context_after:             // emitting additional spurious errors, since we're guaranteed