{"abstract":"Joining branch intervals discards a reachable endpoint.","category":"Static analysis soundness","checks":7,"contract":"Join two integer closed intervals or None for unreachable; return a list enclosing their union, or None if both are unreachable.","contract_signature":"a, b","evaluation_group":"model-caaa8d4b2cf001fa","failed_approach":"Taking only the first reachable interval still discards values from the second branch.","family":"z-static_analysis-interval-join","id":"FA-11491","implementations":{"attempt":{"sha256":"a5c924dc1974cbf2b025d7571598c9c326eacdccecd3f1e6321d17d2c324caab","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(a, b):\n    return a if a is not None else b\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('disjoint branches',solve([0,N],[N+2,N+3]),[0,N+3])\ncheck('nested second branch',solve([0,N+4],[1,N+2]),[0,N+4])\ncheck('second expands lower bound',solve([0,N],[-N,0]),[-N,N])\ncheck('left unreachable',solve(None,[N,N]),[N,N])\ncheck('right unreachable',solve([N,N],None),[N,N])\ncheck('both unreachable',solve(None,None),None)\ncheck('identical singleton',solve([N,N],[N,N]),[N,N])\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":"3171a6c2d70616d4445fab425bcdc1078a832bc1a6be299ee5f44bddd3a9e85d","source":"\"\"\"Failure Map reference implementation. Python standard library only.\"\"\"\nimport json\n\nN = 1\nobservations = []\ndef solve(a, b):\n    if a is None: return b\n    if b is None: return a\n    return [max(a[0],b[0]), min(a[1],b[1])]\ndef check(label, actual, expected):\n    observations.append({\"check\": label, \"actual\": actual, \"expected\": expected, \"passed\": actual == expected})\ncheck('disjoint branches',solve([0,N],[N+2,N+3]),[0,N+3])\ncheck('nested second branch',solve([0,N+4],[1,N+2]),[0,N+4])\ncheck('second expands lower bound',solve([0,N],[-N,0]),[-N,N])\ncheck('left unreachable',solve(None,[N,N]),[N,N])\ncheck('right unreachable',solve([N,N],None),[N,N])\ncheck('both unreachable',solve(None,None),None)\ncheck('identical singleton',solve([N,N],[N,N]),[N,N])\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":"z-static_analysis-interval-join","generated_at":"2026-09-29T14:38:48.438447+00:00","license":"CC0-1.0","python":"3.12.14","seed":1,"split":"open-access"},"relevance":"A deterministic offline analysis model exposing a specific soundness or precision boundary; it does not implement a complete language analyzer.","root_cause":"The join intersects alternative outcomes instead of enclosing both.","sha256":"e994b4287901ff36543b94d79d756d3a33c418597e18a30f707f70cca405ad7e","title":"Joining branch intervals discards a reachable endpoint · case 01","variant":1,"variant_policy":"Five numbered records share a model and may reuse boundary fixtures.","verified":true,"visibility":"public","verification":{"attempt":{"elapsed_ms":39.901,"exit_code":1,"observations":[{"actual":[0,1],"check":"disjoint branches","expected":[0,4],"passed":false},{"actual":[0,5],"check":"nested second branch","expected":[0,5],"passed":true},{"actual":[0,1],"check":"second expands lower bound","expected":[-1,1],"passed":false},{"actual":[1,1],"check":"left unreachable","expected":[1,1],"passed":true},{"actual":[1,1],"check":"right unreachable","expected":[1,1],"passed":true},{"actual":null,"check":"both unreachable","expected":null,"passed":true},{"actual":[1,1],"check":"identical singleton","expected":[1,1],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"disjoint branches\", \"actual\": [0, 1], \"expected\": [0, 4], \"passed\": false}, {\"check\": \"nested second branch\", \"actual\": [0, 5], \"expected\": [0, 5], \"passed\": true}, {\"check\": \"second expands lower bound\", \"actual\": [0, 1], \"expected\": [-1, 1], \"passed\": false}, {\"check\": \"left unreachable\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"right unreachable\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"both unreachable\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"identical singleton\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}], \"passed\": false}\n"},"broken":{"elapsed_ms":39.454,"exit_code":1,"observations":[{"actual":[3,1],"check":"disjoint branches","expected":[0,4],"passed":false},{"actual":[1,3],"check":"nested second branch","expected":[0,5],"passed":false},{"actual":[0,0],"check":"second expands lower bound","expected":[-1,1],"passed":false},{"actual":[1,1],"check":"left unreachable","expected":[1,1],"passed":true},{"actual":[1,1],"check":"right unreachable","expected":[1,1],"passed":true},{"actual":null,"check":"both unreachable","expected":null,"passed":true},{"actual":[1,1],"check":"identical singleton","expected":[1,1],"passed":true}],"passed":false,"stderr":"","stdout":"{\"observations\": [{\"check\": \"disjoint branches\", \"actual\": [3, 1], \"expected\": [0, 4], \"passed\": false}, {\"check\": \"nested second branch\", \"actual\": [1, 3], \"expected\": [0, 5], \"passed\": false}, {\"check\": \"second expands lower bound\", \"actual\": [0, 0], \"expected\": [-1, 1], \"passed\": false}, {\"check\": \"left unreachable\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"right unreachable\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}, {\"check\": \"both unreachable\", \"actual\": null, \"expected\": null, \"passed\": true}, {\"check\": \"identical singleton\", \"actual\": [1, 1], \"expected\": [1, 1], \"passed\": true}], \"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."}}