syntax_data: {"ast_node_type":"variable","tokens":[{"end":31,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let ty = match opt_ty {
context_before:         let opt_ty = self.args.get(p.index() as usize).map(|arg| arg.kind());
context_after:             Some(ty::GenericArgKind::Type(ty)) => ty,