syntax_data: {"ast_node_type":"other","tokens":[{"end":64,"kind":"keyword","start":0,"text":"PatKind::AscribeUserType"}]}
source_snippet:                 PatKind::AscribeUserType { subpattern, .. } => {
context_before:                 PatKind::Binding { var, ty, .. } => break Ok((*var, *ty, pat.span)),
context_after:                     pat = subpattern;