syntax_data: {"ast_node_type":"variable","tokens":[{"end":87,"kind":"keyword","start":0,"text":"while"}]}
source_snippet:         while let PatKind::AscribeUserType { ref subpattern, .. } = unpeeled_pat.kind {
context_before:         let mut unpeeled_pat = pat;
context_after:             unpeeled_pat = subpattern;