{"abstract":"Adds a setter and unexpectedly converts the non-data descriptor into a data descriptor and changes the required Python-language result.","category":"Descriptor lookup","checks":4,"contract":"An instance dictionary field shadows a non-data descriptor. Assignment creates a shadow, deleting the shadow restores computed descriptor reads, and class access stays class. Return reads and final instance dictionary. Inputs use the finite Python types shown in the fixtures. An error string denotes the specified caught exception, not an unhandled process failure.","evaluation_group":"xl-nondata-descriptor-shadow","failed_approach":"The alternative still fails because it manually calls the descriptor and ignores legal instance shadows.","family":"xl-nondata-descriptor-shadow-accidental-data-descriptor","id":"FA-4981","implementations":{"attempt":{"sha256":"335989de2b8dab20a425baded7f44f20c9c62a4b8dd72600cc5350e989d8815a","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self,obj,owner):\n            return 'class' if obj is None else 'computed'\n        pass\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(C.__dict__['field'].__get__(c,C))\n        elif op=='set': c.field=value\n        elif op=='delete': c.__dict__.pop('field',None)\n        elif op=='class': out.append(C.field)\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('initial shadow', solve({'field': 'local'}, [['get', None]]), [['local'], {'field': 'local'}])\ncheck('assign then unshadow', solve({}, [['get', None], ['set', 'local'], ['get', None], ['delete', None], ['get', None], ['class', None]]), [['computed', 'local', 'computed', 'class'], {}])\ncheck('false shadow', solve({'field': 0}, [['get', None]]), [[0], {'field': 0}])\ncheck('None shadow', solve({'field': None}, [['get', None], ['class', None]]), [[None, 'class'], {'field': None}])\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":"8fb1eb6fe77296ef2b7bea1108e2533a8af659c2bfc15eac7c2ebbb00e77b82e","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self,obj,owner):\n            return 'class' if obj is None else 'computed'\n        def __set__(self,obj,value): obj.__dict__['field']=value\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(c.field)\n        elif op=='set': c.field=value\n        elif op=='delete': c.__dict__.pop('field',None)\n        elif op=='class': out.append(C.field)\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('initial shadow', solve({'field': 'local'}, [['get', None]]), [['local'], {'field': 'local'}])\ncheck('assign then unshadow', solve({}, [['get', None], ['set', 'local'], ['get', None], ['delete', None], ['get', None], ['class', None]]), [['computed', 'local', 'computed', 'class'], {}])\ncheck('false shadow', solve({'field': 0}, [['get', None]]), [[0], {'field': 0}])\ncheck('None shadow', solve({'field': None}, [['get', None], ['class', None]]), [[None, 'class'], {'field': None}])\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"},"fixed":{"sha256":"13859b50cb2ff699abd0d0b67b5058927e5438934c3e1751ada880c7ad5b8c60","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(initial, commands):\n    class D:\n        def __get__(self,obj,owner):\n            return 'class' if obj is None else 'computed'\n        pass\n    class C:\n        field=D()\n    c=C(); c.__dict__.update(initial); out=[]\n    for op,value in commands:\n        if op=='get': out.append(c.field)\n        elif op=='set': c.field=value\n        elif op=='delete': c.__dict__.pop('field',None)\n        elif op=='class': out.append(C.field)\n    return [out,dict(c.__dict__)]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('initial shadow', solve({'field': 'local'}, [['get', None]]), [['local'], {'field': 'local'}])\ncheck('assign then unshadow', solve({}, [['get', None], ['set', 'local'], ['get', None], ['delete', None], ['get', None], ['class', None]]), [['computed', 'local', 'computed', 'class'], {}])\ncheck('false shadow', solve({'field': 0}, [['get', None]]), [[0], {'field': 0}])\ncheck('None shadow', solve({'field': None}, [['get', None], ['class', None]]), [[None, 'class'], {'field': None}])\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":"xl-nondata-descriptor-shadow-accidental-data-descriptor","generated_at":"2026-09-29T14:37:44.941883+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"Runs Python standard-library language operations in a deterministic local reproducer. Literal expected answers are authored independently. Related defects share an evaluation group to avoid benchmark split leakage.","repair":"An instance dictionary field shadows a non-data descriptor. Assignment creates a shadow, deleting the shadow restores computed descriptor reads, and class access stays class. Return reads and final instance dictionary.","root_cause":"Adds a setter and unexpectedly converts the non-data descriptor into a data descriptor. The executable reproducer isolates this operation from the rest of the contract.","sha256":"10ac34ae16e14146a8558d916182467e569c14ba5e648c3badd85341796df8f2","title":"Nondata descriptor shadow: Adds a setter and unexpectedly converts the non-data descriptor into a data descriptor · case 01","variant":1,"variant_policy":"The five numbered cases rerun the same authored boundary fixtures; they are reproducibility runs, not independent input variants.","verification":{"attempt":{"elapsed_ms":36.802,"exit_code":1,"observations":[{"actual":[["computed"],{"field":"local"}],"check":"initial shadow","expected":[["local"],{"field":"local"}],"passed":false},{"actual":[["computed","computed","computed","class"],{}],"check":"assign then unshadow","expected":[["computed","local","computed","class"],{}],"passed":false},{"actual":[["computed"],{"field":0}],"check":"false shadow","expected":[[0],{"field":0}],"passed":false},{"actual":[["computed","class"],{"field":null}],"check":"None shadow","expected":[[null,"class"],{"field":null}],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"initial shadow\", \"actual\": [[\"computed\"], {\"field\": \"local\"}], \"expected\": [[\"local\"], {\"field\": \"local\"}], \"passed\": false}, {\"check\": \"assign then unshadow\", \"actual\": [[\"computed\", \"computed\", \"computed\", \"class\"], {}], \"expected\": [[\"computed\", \"local\", \"computed\", \"class\"], {}], \"passed\": false}, {\"check\": \"false shadow\", \"actual\": [[\"computed\"], {\"field\": 0}], \"expected\": [[0], {\"field\": 0}], \"passed\": false}, {\"check\": \"None shadow\", \"actual\": [[\"computed\", \"class\"], {\"field\": null}], \"expected\": [[null, \"class\"], {\"field\": null}], \"passed\": false}], \"passed\": false}\n"},"broken":{"elapsed_ms":41.96,"exit_code":1,"observations":[{"actual":[["computed"],{"field":"local"}],"check":"initial shadow","expected":[["local"],{"field":"local"}],"passed":false},{"actual":[["computed","computed","computed","class"],{}],"check":"assign then unshadow","expected":[["computed","local","computed","class"],{}],"passed":false},{"actual":[["computed"],{"field":0}],"check":"false shadow","expected":[[0],{"field":0}],"passed":false},{"actual":[["computed","class"],{"field":null}],"check":"None shadow","expected":[[null,"class"],{"field":null}],"passed":false}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"initial shadow\", \"actual\": [[\"computed\"], {\"field\": \"local\"}], \"expected\": [[\"local\"], {\"field\": \"local\"}], \"passed\": false}, {\"check\": \"assign then unshadow\", \"actual\": [[\"computed\", \"computed\", \"computed\", \"class\"], {}], \"expected\": [[\"computed\", \"local\", \"computed\", \"class\"], {}], \"passed\": false}, {\"check\": \"false shadow\", \"actual\": [[\"computed\"], {\"field\": 0}], \"expected\": [[0], {\"field\": 0}], \"passed\": false}, {\"check\": \"None shadow\", \"actual\": [[\"computed\", \"class\"], {\"field\": null}], \"expected\": [[null, \"class\"], {\"field\": null}], \"passed\": false}], \"passed\": false}\n"},"fixed":{"elapsed_ms":38.037,"exit_code":0,"observations":[{"actual":[["local"],{"field":"local"}],"check":"initial shadow","expected":[["local"],{"field":"local"}],"passed":true},{"actual":[["computed","local","computed","class"],{}],"check":"assign then unshadow","expected":[["computed","local","computed","class"],{}],"passed":true},{"actual":[[0],{"field":0}],"check":"false shadow","expected":[[0],{"field":0}],"passed":true},{"actual":[[null,"class"],{"field":null}],"check":"None shadow","expected":[[null,"class"],{"field":null}],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"initial shadow\", \"actual\": [[\"local\"], {\"field\": \"local\"}], \"expected\": [[\"local\"], {\"field\": \"local\"}], \"passed\": true}, {\"check\": \"assign then unshadow\", \"actual\": [[\"computed\", \"local\", \"computed\", \"class\"], {}], \"expected\": [[\"computed\", \"local\", \"computed\", \"class\"], {}], \"passed\": true}, {\"check\": \"false shadow\", \"actual\": [[0], {\"field\": 0}], \"expected\": [[0], {\"field\": 0}], \"passed\": true}, {\"check\": \"None shadow\", \"actual\": [[null, \"class\"], {\"field\": null}], \"expected\": [[null, \"class\"], {\"field\": null}], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}