{"abstract":"The operation returns a result or retained state that violates this contract: Repeat one mutable list n times, mutate its first repeated reference, and report all repetitions; they alias the same object.","category":"Iterator consumption","checks":4,"contract":"Repeat one mutable list n times, mutate its first repeated reference, and report all repetitions; they alias the same object. Inputs are the finite Python values shown by the executable fixtures; no concurrent execution is assumed.","contract_signature":"x, y=None","evaluation_group":"model-f7e4eb32e6b66f29","failed_approach":"Independent unmodified copies omit both shared identity and the required mutation.","family":"xr-repeat-retains-object-identity","id":"FA-4586","implementations":{"attempt":{"sha256":"6fe4d8e24294a23218d5baf1bfdf26e103a49f6d6159177869c4e16937a21414","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport itertools as it\nfrom collections import deque\nN = 1\nobservations = []\ndef solve(x, y=None):\n    r=[list(x) for _ in range(y)]\n    return r\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('repeated alias', solve(['a'], 2), [['a', 'new'], ['a', 'new']])\ncheck('single alias', solve([], 1), [['new']])\ncheck('zero repeats', solve(['a'], 0), [])\ncheck('three aliases', solve([], 3), [['new'], ['new'], ['new']])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"},"broken":{"sha256":"b558a3606edf06899e11d99c7e0a4f3a8c1d06358dd7e0a8997793492b6474ab","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\nimport itertools as it\nfrom collections import deque\nN = 1\nobservations = []\ndef solve(x, y=None):\n    r=[list(x) for _ in range(y)]\n    if r: r[0].append(\"new\")\n    return r\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('repeated alias', solve(['a'], 2), [['a', 'new'], ['a', 'new']])\ncheck('single alias', solve([], 1), [['new']])\ncheck('zero repeats', solve(['a'], 0), [])\ncheck('three aliases', solve([], 3), [['new'], ['new'], ['new']])\nprint(json.dumps({\"observations\": observations, \"passed\": all(x[\"passed\"] for x in observations)}, ensure_ascii=False))\nraise SystemExit(0 if all(x[\"passed\"] for x in observations) else 1)\n"}},"limitations":" This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.","method":"Deterministic executable model with adversarial boundary fixtures.","provenance":{"created_by":"Failure Map","dependencies":"Python standard library","family":"xr-repeat-retains-object-identity","generated_at":"2026-09-29T14:37:40.808450+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A controlled local-runtime regression for collection APIs, language semantics, or ownership wrappers. Fixtures include boundary and interaction cases.","root_cause":"Constructing a fresh list per repetition changes aliasing semantics.","sha256":"ac65363481cb8c2646f022aad57e52f4ee747311bac448a834cea30d3a8f9237","title":"Repeat retains object identity · case 01","variant":1,"variant_policy":"Five execution reruns of a fixed adversarial fixture suite; variant number does not alter semantic inputs.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.06,"exit_code":1,"observations":[{"actual":[["a"],["a"]],"check":"repeated alias","expected":[["a","new"],["a","new"]],"passed":false},{"actual":[[]],"check":"single alias","expected":[["new"]],"passed":false},{"actual":[],"check":"zero repeats","expected":[],"passed":true},{"actual":[[],[],[]],"check":"three aliases","expected":[["new"],["new"],["new"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"repeated alias\", \"actual\": [[\"a\"], [\"a\"]], \"expected\": [[\"a\", \"new\"], [\"a\", \"new\"]], \"passed\": false}, {\"check\": \"single alias\", \"actual\": [[]], \"expected\": [[\"new\"]], \"passed\": false}, {\"check\": \"zero repeats\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"three aliases\", \"actual\": [[], [], []], \"expected\": [[\"new\"], [\"new\"], [\"new\"]], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":37.207,"exit_code":1,"observations":[{"actual":[["a","new"],["a"]],"check":"repeated alias","expected":[["a","new"],["a","new"]],"passed":false},{"actual":[["new"]],"check":"single alias","expected":[["new"]],"passed":true},{"actual":[],"check":"zero repeats","expected":[],"passed":true},{"actual":[["new"],[],[]],"check":"three aliases","expected":[["new"],["new"],["new"]],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"repeated alias\", \"actual\": [[\"a\", \"new\"], [\"a\"]], \"expected\": [[\"a\", \"new\"], [\"a\", \"new\"]], \"passed\": false}, {\"check\": \"single alias\", \"actual\": [[\"new\"]], \"expected\": [[\"new\"]], \"passed\": true}, {\"check\": \"zero repeats\", \"actual\": [], \"expected\": [], \"passed\": true}, {\"check\": \"three aliases\", \"actual\": [[\"new\"], [], []], \"expected\": [[\"new\"], [\"new\"], [\"new\"]], \"passed\": false}], \"passed\": false}\n"}},"member_only":{"stages":["fixed"],"fields":["implementations.fixed","verification.fixed","harness","repair"],"note":"The verified repair, its recorded checks, the repair description, and the scoring harness are available to members."}}