syntax_data: {"ast_node_type":"other","tokens":[{"end":81,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // `previous_stack` stores a `PolyTraitObligation`, while `obligation` is
context_before:         debug_assert!(!self.infcx.next_trait_solver());
context_after:         // a `PredicateObligation`. These are distinct types, so we can't