syntax_data: {"ast_node_type":"other","tokens":[{"end":31,"kind":"keyword","start":0,"text":"///"}]}
source_snippet:     ///     (false, true) => {}
context_before:     ///     //~^ ERROR cannot use `y.1` because it was mutably borrowed
context_after:     ///     // Borrowck must not know we don't test `y.1` when `y.0` is `true`.