syntax_data: {"ast_node_type":"other","tokens":[{"end":76,"kind":"keyword","start":0,"text":"//"}]}
source_snippet: // The provided closure will be invoked to deserialize a `SyntaxContextData`
context_before: // to track which `SyntaxContext`s we have already decoded.
context_after: // if we haven't already seen the id of the `SyntaxContext` we are deserializing.