syntax_data: {"ast_node_type":"other","tokens":[{"end":59,"kind":"keyword","start":0,"text":"ty::ExistentialPredicate::AutoTrait(a),"}]}
source_snippet:                     ty::ExistentialPredicate::AutoTrait(a),
context_before:                 (
context_after:                     ty::ExistentialPredicate::AutoTrait(b),