syntax_data: {"ast_node_type":"other","tokens":[{"end":68,"kind":"keyword","start":0,"text":"this.upvars.len()"}]}
source_snippet:                             this.upvars.len() > upvar_index.index(),
context_before:                         debug_assert!(
context_after:                             "Unexpected capture place, upvars={:#?}, upvar_index={:?}",