syntax_data: {"ast_node_type":"function","tokens":[{"end":26,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn default() -> Self {
context_before: impl<'tcx> Default for ProvisionalEvaluationCache<'tcx> {
context_after:         Self { dfn: Cell::new(0), map: Default::default(), wf_args: Default::default() }