syntax_data: {"ast_node_type":"other","tokens":[{"end":30,"kind":"keyword","start":0,"text":"\"ast-tree\""}]}
source_snippet:         "ast-tree" => AstTree,
context_before:         "expanded,hygiene" => Source(PpSourceMode::ExpandedHygiene),
context_after:         "ast-tree,expanded" => AstTreeExpanded,