{"abstract":"Accepts the keyword-only parameter positionally and changes the required Python-language result.","category":"Call argument binding","checks":6,"contract":"Call f(a, *, b=10) and return [a,b]. Reject extra positional arguments, unknown keywords and repeated binding of a. 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-keyword-only-binding","failed_approach":"The alternative still fails because it forbids legal keyword binding of the first parameter.","family":"xl-keyword-only-binding-positional-acceptance","id":"FA-4856","implementations":{"attempt":{"sha256":"161e5dfd27ccb82b917ce4a3834ff0ee04eb2d1227aedbb040ea2fdc3ae59bae","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(args, kwargs):\n    def f(a, /, *, b=10):\n        return [a,b]\n    try:\n        return f(*args, **kwargs)\n    except TypeError:\n        return \"TypeError\"\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('second positional rejected', solve([1, 2], {}), 'TypeError')\ncheck('all named', solve([], {'a': 1, 'b': 2}), [1, 2])\ncheck('optional omitted', solve([1], {}), [1, 10])\ncheck('unknown name', solve([1], {'c': 3}), 'TypeError')\ncheck('a bound twice', solve([1], {'a': 2}), 'TypeError')\ncheck('explicit None', solve([None], {'b': None}), [None, 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":"fe36397a770e1b1f101c3a8c53da9c75db6107395e285e432d6df01efd494876","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(args, kwargs):\n    def f(a, b=10):\n        return [a,b]\n    try:\n        return f(*args, **kwargs)\n    except TypeError:\n        return \"TypeError\"\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('second positional rejected', solve([1, 2], {}), 'TypeError')\ncheck('all named', solve([], {'a': 1, 'b': 2}), [1, 2])\ncheck('optional omitted', solve([1], {}), [1, 10])\ncheck('unknown name', solve([1], {'c': 3}), 'TypeError')\ncheck('a bound twice', solve([1], {'a': 2}), 'TypeError')\ncheck('explicit None', solve([None], {'b': None}), [None, 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":"9c02d25496faa5bb1fd109dd76ed2b2ffc3bdc873b6d14978860386fb86b583c","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(args, kwargs):\n    def f(a, *, b=10):\n        return [a,b]\n    try:\n        return f(*args, **kwargs)\n    except TypeError:\n        return \"TypeError\"\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('second positional rejected', solve([1, 2], {}), 'TypeError')\ncheck('all named', solve([], {'a': 1, 'b': 2}), [1, 2])\ncheck('optional omitted', solve([1], {}), [1, 10])\ncheck('unknown name', solve([1], {'c': 3}), 'TypeError')\ncheck('a bound twice', solve([1], {'a': 2}), 'TypeError')\ncheck('explicit None', solve([None], {'b': None}), [None, 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-keyword-only-binding-positional-acceptance","generated_at":"2026-09-29T14:37:43.622692+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":"Call f(a, *, b=10) and return [a,b]. Reject extra positional arguments, unknown keywords and repeated binding of a.","root_cause":"Accepts the keyword-only parameter positionally. The executable reproducer isolates this operation from the rest of the contract.","sha256":"272e302062bf5ff8956d2f2c5252bf1b5c6a46c0b1b60c4242e97f44d717113a","title":"Keyword only binding: Accepts the keyword-only parameter positionally · 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":44.322,"exit_code":1,"observations":[{"actual":"TypeError","check":"second positional rejected","expected":"TypeError","passed":true},{"actual":"TypeError","check":"all named","expected":[1,2],"passed":false},{"actual":[1,10],"check":"optional omitted","expected":[1,10],"passed":true},{"actual":"TypeError","check":"unknown name","expected":"TypeError","passed":true},{"actual":"TypeError","check":"a bound twice","expected":"TypeError","passed":true},{"actual":[null,null],"check":"explicit None","expected":[null,null],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"second positional rejected\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"all named\", \"actual\": \"TypeError\", \"expected\": [1, 2], \"passed\": false}, {\"check\": \"optional omitted\", \"actual\": [1, 10], \"expected\": [1, 10], \"passed\": true}, {\"check\": \"unknown name\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"a bound twice\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"explicit None\", \"actual\": [null, null], \"expected\": [null, null], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":42.021,"exit_code":1,"observations":[{"actual":[1,2],"check":"second positional rejected","expected":"TypeError","passed":false},{"actual":[1,2],"check":"all named","expected":[1,2],"passed":true},{"actual":[1,10],"check":"optional omitted","expected":[1,10],"passed":true},{"actual":"TypeError","check":"unknown name","expected":"TypeError","passed":true},{"actual":"TypeError","check":"a bound twice","expected":"TypeError","passed":true},{"actual":[null,null],"check":"explicit None","expected":[null,null],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"second positional rejected\", \"actual\": [1, 2], \"expected\": \"TypeError\", \"passed\": false}, {\"check\": \"all named\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"optional omitted\", \"actual\": [1, 10], \"expected\": [1, 10], \"passed\": true}, {\"check\": \"unknown name\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"a bound twice\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"explicit None\", \"actual\": [null, null], \"expected\": [null, null], \"passed\": true}], \"passed\": false}\n"},"fixed":{"elapsed_ms":38.653,"exit_code":0,"observations":[{"actual":"TypeError","check":"second positional rejected","expected":"TypeError","passed":true},{"actual":[1,2],"check":"all named","expected":[1,2],"passed":true},{"actual":[1,10],"check":"optional omitted","expected":[1,10],"passed":true},{"actual":"TypeError","check":"unknown name","expected":"TypeError","passed":true},{"actual":"TypeError","check":"a bound twice","expected":"TypeError","passed":true},{"actual":[null,null],"check":"explicit None","expected":[null,null],"passed":true}],"passed":true,"stderr":"","stdout":"{\"observations\": [{\"check\": \"second positional rejected\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"all named\", \"actual\": [1, 2], \"expected\": [1, 2], \"passed\": true}, {\"check\": \"optional omitted\", \"actual\": [1, 10], \"expected\": [1, 10], \"passed\": true}, {\"check\": \"unknown name\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"a bound twice\", \"actual\": \"TypeError\", \"expected\": \"TypeError\", \"passed\": true}, {\"check\": \"explicit None\", \"actual\": [null, null], \"expected\": [null, null], \"passed\": true}], \"passed\": true}\n"}},"verified":true,"visibility":"public"}