FA-5116 / Method resolution / Open access

Classmethod dynamic binding: Uses the defining Base class instead of the bound subclass · case 01

Uses the defining Base class instead of the bound subclass and changes the required Python-language result.

Verified by executionVariant 1 · 4 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Uses the defining Base class instead of the bound subclass. The executable reproducer isolates this operation from the rest of the contract.

VERIFIED REPAIR

An inherited classmethod binds the accessing class, including access through an instance or a saved bound method. Return [bound class name,its label,suffix].

Unsuccessful approach: The alternative still fails because it reports the bound class metaclass instead of the class name.

Case contract

An inherited classmethod binds the accessing class, including access through an instance or a saved bound method. Return [bound class name,its label,suffix]. Inputs use the finite Python types shown in the fixtures. An error string denotes the specified caught exception, not an unhandled process failure.

Why this case matters

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.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(mode, suffix):
    class Base:
        label='base'
        @classmethod
        def read(cls,suffix): return ['Base',Base.label,suffix]
    class Child(Base): label='child'
    try:
        if mode=='base': return Base.read(suffix)
        if mode=='child': return Child.read(suffix)
        if mode=='instance': return Child().read(suffix)
        bound=Child.read
        return bound(suffix)
    except (TypeError,AttributeError) as exc:
        return type(exc).__name__
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('base access', solve('base', 'x'), ['Base', 'base', 'x'])
check('subclass access', solve('child', 'y'), ['Child', 'child', 'y'])
check('instance access', solve('instance', None), ['Child', 'child', None])
check('saved bound method', solve('saved', 0), ['Child', 'child', 0])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
base access	`['Base', 'base', 'x']`	`['Base', 'base', 'x']`	Passed
subclass access	`['Base', 'base', 'y']`	`['Child', 'child', 'y']`	Failed
instance access	`['Base', 'base', None]`	`['Child', 'child', None]`	Failed
saved bound method	`['Base', 'base', 0]`	`['Child', 'child', 0]`	Failed

SHA-256 / 2048e0e5f3858c1098b86aec6e82d41de806f05a23282ce22c4fe22fc444e707

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(mode, suffix):
    class Base:
        label='base'
        @classmethod
        def read(cls,suffix): return [type(cls).__name__,cls.label,suffix]
    class Child(Base): label='child'
    try:
        if mode=='base': return Base.read(suffix)
        if mode=='child': return Child.read(suffix)
        if mode=='instance': return Child().read(suffix)
        bound=Child.read
        return bound(suffix)
    except (TypeError,AttributeError) as exc:
        return type(exc).__name__
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('base access', solve('base', 'x'), ['Base', 'base', 'x'])
check('subclass access', solve('child', 'y'), ['Child', 'child', 'y'])
check('instance access', solve('instance', None), ['Child', 'child', None])
check('saved bound method', solve('saved', 0), ['Child', 'child', 0])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
base access	`['type', 'base', 'x']`	`['Base', 'base', 'x']`	Failed
subclass access	`['type', 'child', 'y']`	`['Child', 'child', 'y']`	Failed
instance access	`['type', 'child', None]`	`['Child', 'child', None]`	Failed
saved bound method	`['type', 'child', 0]`	`['Child', 'child', 0]`	Failed

SHA-256 / e80ebf3120618dc53b7a2e38fae56b40d501c2b35975a7d875e6c26e41054999

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(mode, suffix):
    class Base:
        label='base'
        @classmethod
        def read(cls,suffix): return [cls.__name__,cls.label,suffix]
    class Child(Base): label='child'
    try:
        if mode=='base': return Base.read(suffix)
        if mode=='child': return Child.read(suffix)
        if mode=='instance': return Child().read(suffix)
        bound=Child.read
        return bound(suffix)
    except (TypeError,AttributeError) as exc:
        return type(exc).__name__
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('base access', solve('base', 'x'), ['Base', 'base', 'x'])
check('subclass access', solve('child', 'y'), ['Child', 'child', 'y'])
check('instance access', solve('instance', None), ['Child', 'child', None])
check('saved bound method', solve('saved', 0), ['Child', 'child', 0])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
base access	`['Base', 'base', 'x']`	`['Base', 'base', 'x']`	Passed
subclass access	`['Child', 'child', 'y']`	`['Child', 'child', 'y']`	Passed
instance access	`['Child', 'child', None]`	`['Child', 'child', None]`	Passed
saved bound method	`['Child', 'child', 0]`	`['Child', 'child', 0]`	Passed

SHA-256 / 7f30de44638b8a60d774a651f2944bc1d879f12c49eeda25f27204a7ea91a750

Verification & scope

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.

Observations recorded using Python 3.12.14 at 2026-09-29T14:37:46.265647+00:00.

Case digest / e77bae31e3943fed61b77e4cf836b4e2343296079bed20d5a55d6108f48c550e