syntax_data: {"ast_node_type":"import","tokens":[{"end":82,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:             //     deref!(false) => {} // not reached because the guard changed it
context_before:             //     _ if { *b = true; false } => {} // not reached because the guard is `false`
context_after:             //     // UB because we reached the unreachable.