https://github.com/rust-lang/rustc-guide/blob/9b3803d35d0e9ee80c0b42ee58ed472b16f06ea8/src/queries/query-evaluation-model-in-detail.md#L117-L123 `let list_of_items` should be `let list_of_hir_items` or `for item_def_id in list_of_hir_items { ` should be `for item_def_id in list_of_items { `