Function is_test_run_receiver 

pub fn is_test_run_receiver(source: &str, run_start: usize) -> bool

#2138: whether the run identifier starting at run_start in source is the test run’s run — inside a suite’s case body, with no binder of its own in scope there. #2175: the scope is the checker’s: a let earlier in any enclosing block, a lambda parameter, a match arm’s pattern, or an is <pattern> test’s bindings all shadow it. #2181: an is test binds where the checker says it does (bynk_check::narrowing): in an if’s then block when the condition holds, in its else block when it fails (if !(v is Some(run)) { … } else { run.id }), and on the right of && and implies (v is Some(run) && run.id == "x").