syntax_data: {"ast_node_type":"variable","tokens":[{"end":81,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let kind = self.lower_variant_or_leaf(res, id, span, ty, vec![]);
context_before:                 // be a unit struct or unit variant (e.g. `Option::None`).
context_after:                 return Box::new(Pat { span, ty, kind });