syntax_data: {"ast_node_type":"other","tokens":[{"end":71,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // Use a type that can't appear in defaults of type parameters.
context_before:     ty::ExistentialTraitRef<'tcx> {
context_after:         let dummy_self = Ty::new_fresh(p.tcx(), 0);