FA-43406 / Borrow checking / Open access
An unactivated reservation is usable as a mutable reference · case 01
An unactivated reservation is usable as a mutable reference.
ROOT CAUSE
The static analyzer mishandles reserved write: an unactivated reservation is usable as a mutable reference.
VERIFIED REPAIR
Apply the specified transfer or inference rule at this site: if bool(d['reserved_writes']): errors.append('reserved-write').
Unsuccessful approach: The partial repair uses if len(d['reserved_writes'])>1: errors.append('reserved-write'), which still violates the stipulated analysis contract.
Case contract
Validate reservation/activation facts of a toy two-phase mutable loan. Activation requires prior reservation, dominance and same loan identity. Reserved loan cannot be written through. Shared reads may exist during reservation but not activation. Reservation cannot cross storage death. Activation occurs at most once per path. Only compiler-generated method receiver auto-borrows may be two-phase. Argument evaluation must complete before activation. Canceled calls must release reservations. Input is a fully explicit descriptor of the stated toy IR. Return rule identifiers in declaration order; absent optional obligations use the provided neutral defaults. No rule is an assertion about a production language.
Why this case matters
A finite offline static-analysis model of ownership and borrowing; it does not execute the analyzed program.
1 / The failure
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
errors=[]
if d['activated'] and not d['reserved']: errors.append('reservation-required')
if d['activated'] and not d['dominates']: errors.append('reservation-dominance')
if d['activated'] and d['reservation_id']!=d['activation_id']: errors.append('activation-identity')
if False: errors.append('reserved-write')
if d['activated'] and bool(d['shared_at_activation']): errors.append('activation-shared-conflict')
if bool(set(d['storage_dead'])&set(d['reservation_points'])): errors.append('reservation-storage')
if len(d['activations'])!=len(set(d['activations'])): errors.append('single-activation')
if d['two_phase'] and not d['auto_receiver']: errors.append('eligible-auto-borrow')
if d['activation_point']<d['argument_end']: errors.append('argument-before-activation')
if d['canceled'] and d['reservation_live']: errors.append('cancellation-release')
return errors
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'activated': False, 'reserved': False, 'dominates': True, 'reservation_id': None, 'activation_id': None, 'reserved_writes': [], 'shared_at_activation': [], 'storage_dead': [], 'reservation_points': [], 'activations': [], 'auto_receiver': True, 'two_phase': False, 'argument_end': 0, 'activation_point': 0, 'canceled': False, 'reservation_live': False}
check('well formed empty obligations',solve(base),[])
check('reservation-required regression 0', solve(dict(base, **({'activated':True,'activation_id':'a','reservation_id':'a'}))), ['reservation-required'])
check('reservation-required regression 1', solve(dict(base, **({'activated':True,'activation_id':N,'reservation_id':N}))), ['reservation-required'])
check('reservation-dominance regression 0', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False}))), ['reservation-dominance'])
check('reservation-dominance regression 1', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False,'activation_point':N}))), ['reservation-dominance'])
check('activation-identity regression 0', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':'a','activation_id':'b'}))), ['activation-identity'])
check('activation-identity regression 1', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':N,'activation_id':N+1}))), ['activation-identity'])
check('reserved-write regression 0', solve(dict(base, **({'reserved_writes':[N]}))), ['reserved-write'])
check('reserved-write regression 1', solve(dict(base, **({'reserved_writes':[N+1]}))), ['reserved-write'])
check('activation-shared-conflict regression 0', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':['r']}))), ['activation-shared-conflict'])
check('activation-shared-conflict regression 1', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':[N]}))), ['activation-shared-conflict'])
check('reservation-storage regression 0', solve(dict(base, **({'storage_dead':[N],'reservation_points':[N,N+1]}))), ['reservation-storage'])
check('reservation-storage regression 1', solve(dict(base, **({'storage_dead':[N,N+1],'reservation_points':[N]}))), ['reservation-storage'])
check('single-activation regression 0', solve(dict(base, **({'activations':['r','r']}))), ['single-activation'])
check('single-activation regression 1', solve(dict(base, **({'activations':[N,N]}))), ['single-activation'])
check('eligible-auto-borrow regression 0', solve(dict(base, **({'two_phase':True,'auto_receiver':False}))), ['eligible-auto-borrow'])
check('eligible-auto-borrow regression 1', solve(dict(base, **({'two_phase':True,'auto_receiver':False,'argument_end':0,'activation_point':N}))), ['eligible-auto-borrow'])
check('argument-before-activation regression 0', solve(dict(base, **({'activation_point':N,'argument_end':N+1}))), ['argument-before-activation'])
check('argument-before-activation regression 1', solve(dict(base, **({'activation_point':N+1,'argument_end':N+2}))), ['argument-before-activation'])
check('cancellation-release regression 0', solve(dict(base, **({'canceled':True,'reservation_live':True}))), ['cancellation-release'])
check('cancellation-release regression 1', solve(dict(base, **({'canceled':True,'reservation_live':True,'activation_point':N}))), ['cancellation-release'])
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 |
|---|---|---|---|
| well formed empty obligations | [] | [] | Passed |
| reservation-required regression 0 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-required regression 1 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-dominance regression 0 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| reservation-dominance regression 1 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| activation-identity regression 0 | ['activation-identity'] | ['activation-identity'] | Passed |
| activation-identity regression 1 | ['activation-identity'] | ['activation-identity'] | Passed |
| reserved-write regression 0 | [] | ['reserved-write'] | Failed |
| reserved-write regression 1 | [] | ['reserved-write'] | Failed |
| activation-shared-conflict regression 0 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| activation-shared-conflict regression 1 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| reservation-storage regression 0 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| reservation-storage regression 1 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| single-activation regression 0 | ['single-activation'] | ['single-activation'] | Passed |
| single-activation regression 1 | ['single-activation'] | ['single-activation'] | Passed |
| eligible-auto-borrow regression 0 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| eligible-auto-borrow regression 1 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| argument-before-activation regression 0 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| argument-before-activation regression 1 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| cancellation-release regression 0 | ['cancellation-release'] | ['cancellation-release'] | Passed |
| cancellation-release regression 1 | ['cancellation-release'] | ['cancellation-release'] | Passed |
SHA-256 / 9677b889168d8c718f30d025e471c7e63c74cd6f3523250df48c057dde59df43
2 / The unsuccessful fix
Exit 1"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
errors=[]
if d['activated'] and not d['reserved']: errors.append('reservation-required')
if d['activated'] and not d['dominates']: errors.append('reservation-dominance')
if d['activated'] and d['reservation_id']!=d['activation_id']: errors.append('activation-identity')
if len(d['reserved_writes'])>1: errors.append('reserved-write')
if d['activated'] and bool(d['shared_at_activation']): errors.append('activation-shared-conflict')
if bool(set(d['storage_dead'])&set(d['reservation_points'])): errors.append('reservation-storage')
if len(d['activations'])!=len(set(d['activations'])): errors.append('single-activation')
if d['two_phase'] and not d['auto_receiver']: errors.append('eligible-auto-borrow')
if d['activation_point']<d['argument_end']: errors.append('argument-before-activation')
if d['canceled'] and d['reservation_live']: errors.append('cancellation-release')
return errors
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'activated': False, 'reserved': False, 'dominates': True, 'reservation_id': None, 'activation_id': None, 'reserved_writes': [], 'shared_at_activation': [], 'storage_dead': [], 'reservation_points': [], 'activations': [], 'auto_receiver': True, 'two_phase': False, 'argument_end': 0, 'activation_point': 0, 'canceled': False, 'reservation_live': False}
check('well formed empty obligations',solve(base),[])
check('reservation-required regression 0', solve(dict(base, **({'activated':True,'activation_id':'a','reservation_id':'a'}))), ['reservation-required'])
check('reservation-required regression 1', solve(dict(base, **({'activated':True,'activation_id':N,'reservation_id':N}))), ['reservation-required'])
check('reservation-dominance regression 0', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False}))), ['reservation-dominance'])
check('reservation-dominance regression 1', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False,'activation_point':N}))), ['reservation-dominance'])
check('activation-identity regression 0', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':'a','activation_id':'b'}))), ['activation-identity'])
check('activation-identity regression 1', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':N,'activation_id':N+1}))), ['activation-identity'])
check('reserved-write regression 0', solve(dict(base, **({'reserved_writes':[N]}))), ['reserved-write'])
check('reserved-write regression 1', solve(dict(base, **({'reserved_writes':[N+1]}))), ['reserved-write'])
check('activation-shared-conflict regression 0', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':['r']}))), ['activation-shared-conflict'])
check('activation-shared-conflict regression 1', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':[N]}))), ['activation-shared-conflict'])
check('reservation-storage regression 0', solve(dict(base, **({'storage_dead':[N],'reservation_points':[N,N+1]}))), ['reservation-storage'])
check('reservation-storage regression 1', solve(dict(base, **({'storage_dead':[N,N+1],'reservation_points':[N]}))), ['reservation-storage'])
check('single-activation regression 0', solve(dict(base, **({'activations':['r','r']}))), ['single-activation'])
check('single-activation regression 1', solve(dict(base, **({'activations':[N,N]}))), ['single-activation'])
check('eligible-auto-borrow regression 0', solve(dict(base, **({'two_phase':True,'auto_receiver':False}))), ['eligible-auto-borrow'])
check('eligible-auto-borrow regression 1', solve(dict(base, **({'two_phase':True,'auto_receiver':False,'argument_end':0,'activation_point':N}))), ['eligible-auto-borrow'])
check('argument-before-activation regression 0', solve(dict(base, **({'activation_point':N,'argument_end':N+1}))), ['argument-before-activation'])
check('argument-before-activation regression 1', solve(dict(base, **({'activation_point':N+1,'argument_end':N+2}))), ['argument-before-activation'])
check('cancellation-release regression 0', solve(dict(base, **({'canceled':True,'reservation_live':True}))), ['cancellation-release'])
check('cancellation-release regression 1', solve(dict(base, **({'canceled':True,'reservation_live':True,'activation_point':N}))), ['cancellation-release'])
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 |
|---|---|---|---|
| well formed empty obligations | [] | [] | Passed |
| reservation-required regression 0 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-required regression 1 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-dominance regression 0 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| reservation-dominance regression 1 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| activation-identity regression 0 | ['activation-identity'] | ['activation-identity'] | Passed |
| activation-identity regression 1 | ['activation-identity'] | ['activation-identity'] | Passed |
| reserved-write regression 0 | [] | ['reserved-write'] | Failed |
| reserved-write regression 1 | [] | ['reserved-write'] | Failed |
| activation-shared-conflict regression 0 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| activation-shared-conflict regression 1 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| reservation-storage regression 0 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| reservation-storage regression 1 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| single-activation regression 0 | ['single-activation'] | ['single-activation'] | Passed |
| single-activation regression 1 | ['single-activation'] | ['single-activation'] | Passed |
| eligible-auto-borrow regression 0 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| eligible-auto-borrow regression 1 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| argument-before-activation regression 0 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| argument-before-activation regression 1 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| cancellation-release regression 0 | ['cancellation-release'] | ['cancellation-release'] | Passed |
| cancellation-release regression 1 | ['cancellation-release'] | ['cancellation-release'] | Passed |
SHA-256 / c7edc840989a2e5eb041abe8dc7d2c7d129ed93b1e0f0a219070a605fb67db38
3 / The verified repair
Exit 0"""Failure Map reference implementation. Python standard library only."""
import json
N = 1
observations = []
def solve(d):
errors=[]
if d['activated'] and not d['reserved']: errors.append('reservation-required')
if d['activated'] and not d['dominates']: errors.append('reservation-dominance')
if d['activated'] and d['reservation_id']!=d['activation_id']: errors.append('activation-identity')
if bool(d['reserved_writes']): errors.append('reserved-write')
if d['activated'] and bool(d['shared_at_activation']): errors.append('activation-shared-conflict')
if bool(set(d['storage_dead'])&set(d['reservation_points'])): errors.append('reservation-storage')
if len(d['activations'])!=len(set(d['activations'])): errors.append('single-activation')
if d['two_phase'] and not d['auto_receiver']: errors.append('eligible-auto-borrow')
if d['activation_point']<d['argument_end']: errors.append('argument-before-activation')
if d['canceled'] and d['reservation_live']: errors.append('cancellation-release')
return errors
def check(label, actual, expected):
observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'activated': False, 'reserved': False, 'dominates': True, 'reservation_id': None, 'activation_id': None, 'reserved_writes': [], 'shared_at_activation': [], 'storage_dead': [], 'reservation_points': [], 'activations': [], 'auto_receiver': True, 'two_phase': False, 'argument_end': 0, 'activation_point': 0, 'canceled': False, 'reservation_live': False}
check('well formed empty obligations',solve(base),[])
check('reservation-required regression 0', solve(dict(base, **({'activated':True,'activation_id':'a','reservation_id':'a'}))), ['reservation-required'])
check('reservation-required regression 1', solve(dict(base, **({'activated':True,'activation_id':N,'reservation_id':N}))), ['reservation-required'])
check('reservation-dominance regression 0', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False}))), ['reservation-dominance'])
check('reservation-dominance regression 1', solve(dict(base, **({'activated':True,'reserved':True,'dominates':False,'activation_point':N}))), ['reservation-dominance'])
check('activation-identity regression 0', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':'a','activation_id':'b'}))), ['activation-identity'])
check('activation-identity regression 1', solve(dict(base, **({'activated':True,'reserved':True,'reservation_id':N,'activation_id':N+1}))), ['activation-identity'])
check('reserved-write regression 0', solve(dict(base, **({'reserved_writes':[N]}))), ['reserved-write'])
check('reserved-write regression 1', solve(dict(base, **({'reserved_writes':[N+1]}))), ['reserved-write'])
check('activation-shared-conflict regression 0', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':['r']}))), ['activation-shared-conflict'])
check('activation-shared-conflict regression 1', solve(dict(base, **({'activated':True,'reserved':True,'shared_at_activation':[N]}))), ['activation-shared-conflict'])
check('reservation-storage regression 0', solve(dict(base, **({'storage_dead':[N],'reservation_points':[N,N+1]}))), ['reservation-storage'])
check('reservation-storage regression 1', solve(dict(base, **({'storage_dead':[N,N+1],'reservation_points':[N]}))), ['reservation-storage'])
check('single-activation regression 0', solve(dict(base, **({'activations':['r','r']}))), ['single-activation'])
check('single-activation regression 1', solve(dict(base, **({'activations':[N,N]}))), ['single-activation'])
check('eligible-auto-borrow regression 0', solve(dict(base, **({'two_phase':True,'auto_receiver':False}))), ['eligible-auto-borrow'])
check('eligible-auto-borrow regression 1', solve(dict(base, **({'two_phase':True,'auto_receiver':False,'argument_end':0,'activation_point':N}))), ['eligible-auto-borrow'])
check('argument-before-activation regression 0', solve(dict(base, **({'activation_point':N,'argument_end':N+1}))), ['argument-before-activation'])
check('argument-before-activation regression 1', solve(dict(base, **({'activation_point':N+1,'argument_end':N+2}))), ['argument-before-activation'])
check('cancellation-release regression 0', solve(dict(base, **({'canceled':True,'reservation_live':True}))), ['cancellation-release'])
check('cancellation-release regression 1', solve(dict(base, **({'canceled':True,'reservation_live':True,'activation_point':N}))), ['cancellation-release'])
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 |
|---|---|---|---|
| well formed empty obligations | [] | [] | Passed |
| reservation-required regression 0 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-required regression 1 | ['reservation-required'] | ['reservation-required'] | Passed |
| reservation-dominance regression 0 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| reservation-dominance regression 1 | ['reservation-dominance'] | ['reservation-dominance'] | Passed |
| activation-identity regression 0 | ['activation-identity'] | ['activation-identity'] | Passed |
| activation-identity regression 1 | ['activation-identity'] | ['activation-identity'] | Passed |
| reserved-write regression 0 | ['reserved-write'] | ['reserved-write'] | Passed |
| reserved-write regression 1 | ['reserved-write'] | ['reserved-write'] | Passed |
| activation-shared-conflict regression 0 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| activation-shared-conflict regression 1 | ['activation-shared-conflict'] | ['activation-shared-conflict'] | Passed |
| reservation-storage regression 0 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| reservation-storage regression 1 | ['reservation-storage'] | ['reservation-storage'] | Passed |
| single-activation regression 0 | ['single-activation'] | ['single-activation'] | Passed |
| single-activation regression 1 | ['single-activation'] | ['single-activation'] | Passed |
| eligible-auto-borrow regression 0 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| eligible-auto-borrow regression 1 | ['eligible-auto-borrow'] | ['eligible-auto-borrow'] | Passed |
| argument-before-activation regression 0 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| argument-before-activation regression 1 | ['argument-before-activation'] | ['argument-before-activation'] | Passed |
| cancellation-release regression 0 | ['cancellation-release'] | ['cancellation-release'] | Passed |
| cancellation-release regression 1 | ['cancellation-release'] | ['cancellation-release'] | Passed |
SHA-256 / eca4be6c58130da4519879ebe42d92570bdd4d8b52a6fa1d2fdf7d4a07c27fe4
Verification & scope
The explicitly stated toy language is the complete scope; this is not a production compiler or a claim about Rust semantics. 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 2026-09-29T14:44:01.522502+00:00.
Case digest / 35d02c30f3e77d0a37edd9ac48047737d7fa1ee18f9c8bfdebe1d2a626e100e1