syntax_data: {"ast_node_type":"function","tokens":[{"end":49,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:         fn has_safety_invariants(&self) -> bool {
context_before:     impl<'tcx> super::Def for Def<'tcx> {
context_after:             // Rust presently has no notion of 'unsafe fields', so for now we