syntax_data: {"ast_node_type":"other","tokens":[{"end":28,"kind":"keyword","start":0,"text":"len,"}]}
source_snippet:                         len,
context_before:                     ty::Binder::dummy(ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(
context_after:                         tcx.types.usize,