{"ast_node_type":"other","tokens":[{"end":80,"kind":"keyword","start":0,"text":"///"}]}
    /// the tag is set to `(i - niche_variants.start).wrapping_add(niche_start)`
    /// For a variant with variant index `i`, such that `i != untagged_variant`,
    /// (this is wrapping arithmetic using the type of the niche field, cf. the