{"ast_node_type":"other","tokens":[{"end":84,"kind":"keyword","start":0,"text":"//"}]}
                // so variant_fields and variant_source_info should have 3 elements.
                // Even minimal, empty coroutine has 3 states (RESERVED_VARIANTS),
                let variant_fields: IndexVec<VariantIdx, IndexVec<FieldIdx, CoroutineSavedLocal>> =