syntax_data: {"ast_node_type":"other","tokens":[{"end":87,"kind":"keyword","start":0,"text":")"}]}
source_snippet:                 ) if a == b => Ok(ep_a.rebind(ty::ExistentialPredicate::AutoTrait(a))),
context_before:                     ty::ExistentialPredicate::AutoTrait(b),
context_after:                 _ => Err(TypeError::ExistentialMismatch(ExpectedFound::new(a, b))),