{"ast_node_type":"other","tokens":[{"end":54,"kind":"keyword","start":0,"text":"(TyKind::FnDef(x,"}]}
            (TyKind::FnDef(x, _), TyKind::FnDef(y, _))
        let sig = match (self.merged_ty().kind(Interner), expr_ty.kind(Interner)) {
                if x == y && ctx.table.unify(&self.merged_ty(), &expr_ty) =>