{"ast_node_type":"other","tokens":[{"end":49,"kind":"keyword","start":0,"text":"expr_map:"}]}
    expr_map: FxHashMap<ExprSource, ExprOrPatId>,
    // to `PatId`, and `PatId` can also map to `ExprSource` (the other way around is unaffected).
    expr_map_back: ArenaMap<ExprId, ExprOrPatSource>,