syntax_data: {"ast_node_type":"variable","tokens":[{"end":62,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                 let variant_def = adt_def.variant_of_res(res);
context_before:                 };
context_after:                 let subpatterns = self.lower_tuple_subpats(pats, variant_def.fields.len(), ddpos);