syntax_data: {"ast_node_type":"other","tokens":[{"end":60,"kind":"keyword","start":0,"text":"ty::ExistentialPredicate::Projection(b),"}]}
source_snippet:                     ty::ExistentialPredicate::Projection(b),
context_before:                     ty::ExistentialPredicate::Projection(a),
context_after:                 ) => Ok(ep_a.rebind(ty::ExistentialPredicate::Projection(