{"ast_node_type":"other","tokens":[{"end":50,"kind":"keyword","start":0,"text":"//"}]}
            // First add `Union { .. }` to `self`.
            // Convert a `Union { a: p, b: q }` witness into `Union { a: p }` and `Union { b: q }`.
            self.0.push(WitnessPat::wild_from_ctor(pcx.cx, ctor.clone(), pcx.ty.clone()));