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FA-43156 / Borrow checking / Open access

A consuming closure is incorrectly admitted as repeatedly mutable-callable · case 01

A consuming closure is incorrectly admitted as repeatedly mutable-callable.

Verified by executionVariant 1 · 21 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The static analyzer mishandles once mode: a consuming closure is incorrectly admitted as repeatedly mutable-callable.

THE FAILURE

The static analyzer mishandles once mode: a consuming closure is incorrectly admitted as repeatedly mutable-callable.

Unsuccessful approach: The partial repair uses if bool(d['consumed']) and d['mode']=='Shared': errors.append('once-mode'), which still violates the stipulated analysis contract.

Case contract

Validate an inferred closure environment. Captures contain declared places; overlapping prefix captures must be minimized; unique captures may not be duplicated; consumed captures require Once call mode; mutated captures require Mut or Once; an escaping environment cannot hold stack-only origins; environment region contains all call sites; captured references remain valid for the environment region; captures of packed fields cannot form references; captures of destructor-bearing aggregates cannot be narrowed to moved fields. 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 not set(d['captures'])<=set(d['declared']): errors.append('capture-declaration')
    if any(a!=b and b.startswith(a+'.') for a in d['captures'] for b in d['captures']): errors.append('capture-prefix')
    if len(d['unique'])!=len(set(d['unique'])): errors.append('unique-duplicate')
    if False: errors.append('once-mode')
    if bool(d['mutated']) and d['mode']=='Shared': errors.append('mut-mode')
    if d['escapes'] and bool(set(d['captures'])&set(d['stack'])): errors.append('escape-stack')
    if not set(d['calls'])<=set(d['env']): errors.append('call-region')
    if not set(d['env'])<=set(d['valid']): errors.append('capture-validity')
    if bool(set(d['captures'])&set(d['packed'])): errors.append('packed-reference')
    if any(p.split('.')[0] in d['drop_aggregates'] for p in d['narrow_moves']): errors.append('destructor-narrowing')
    return errors
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'captures': [], 'declared': [], 'unique': [], 'consumed': [], 'mutated': [], 'mode': 'Shared', 'escapes': False, 'stack': [], 'env': [], 'calls': [], 'valid': [], 'packed': [], 'narrow_moves': [], 'drop_aggregates': []}
check('well formed empty obligations',solve(base),[])
check('capture-declaration regression 0', solve(dict(base, **({'captures':['a','b'],'declared':['a']}))), ['capture-declaration'])
check('capture-declaration regression 1', solve(dict(base, **({'captures':['a','x'+str(N)],'declared':['a']}))), ['capture-declaration'])
check('capture-prefix regression 0', solve(dict(base, **({'captures':['r','r.y'],'declared':['r','r.y']}))), ['capture-prefix'])
check('capture-prefix regression 1', solve(dict(base, **({'captures':['r','r.y.z'],'declared':['r','r.y.z']}))), ['capture-prefix'])
check('unique-duplicate regression 0', solve(dict(base, **({'unique':['r','r']}))), ['unique-duplicate'])
check('unique-duplicate regression 1', solve(dict(base, **({'unique':[N,N]}))), ['unique-duplicate'])
check('once-mode regression 0', solve(dict(base, **({'consumed':['x'],'mode':'Mut'}))), ['once-mode'])
check('once-mode regression 1', solve(dict(base, **({'consumed':list(range(N)),'mode':'Mut'}))), ['once-mode'])
check('mut-mode regression 0', solve(dict(base, **({'mutated':['x']}))), ['mut-mode'])
check('mut-mode regression 1', solve(dict(base, **({'mutated':[N]}))), ['mut-mode'])
check('escape-stack regression 0', solve(dict(base, **({'escapes':True,'captures':['a','b'],'declared':['a','b'],'stack':['b']}))), ['escape-stack'])
check('escape-stack regression 1', solve(dict(base, **({'escapes':True,'captures':['a','c'],'declared':['a','c'],'stack':['c']}))), ['escape-stack'])
check('call-region regression 0', solve(dict(base, **({'calls':[N],'env':[N+1],'valid':[N+1]}))), ['call-region'])
check('call-region regression 1', solve(dict(base, **({'calls':[N,N+1],'env':[N+1,N+2],'valid':[N+1,N+2]}))), ['call-region'])
check('capture-validity regression 0', solve(dict(base, **({'env':[N,N+1],'valid':[N]}))), ['capture-validity'])
check('capture-validity regression 1', solve(dict(base, **({'env':[N],'valid':[N+1]}))), ['capture-validity'])
check('packed-reference regression 0', solve(dict(base, **({'captures':['a','b'],'declared':['a','b'],'packed':['b']}))), ['packed-reference'])
check('packed-reference regression 1', solve(dict(base, **({'captures':['a','c'],'declared':['a','c'],'packed':['c']}))), ['packed-reference'])
check('destructor-narrowing regression 0', solve(dict(base, **({'narrow_moves':['r.f'],'drop_aggregates':['r']}))), ['destructor-narrowing'])
check('destructor-narrowing regression 1', solve(dict(base, **({'narrow_moves':['r.f.g'],'drop_aggregates':['r']}))), ['destructor-narrowing'])
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 fixtureActualExpectedOutcome
well formed empty obligations[][]Passed
capture-declaration regression 0['capture-declaration']['capture-declaration']Passed
capture-declaration regression 1['capture-declaration']['capture-declaration']Passed
capture-prefix regression 0['capture-prefix']['capture-prefix']Passed
capture-prefix regression 1['capture-prefix']['capture-prefix']Passed
unique-duplicate regression 0['unique-duplicate']['unique-duplicate']Passed
unique-duplicate regression 1['unique-duplicate']['unique-duplicate']Passed
once-mode regression 0[]['once-mode']Failed
once-mode regression 1[]['once-mode']Failed
mut-mode regression 0['mut-mode']['mut-mode']Passed
mut-mode regression 1['mut-mode']['mut-mode']Passed
escape-stack regression 0['escape-stack']['escape-stack']Passed
escape-stack regression 1['escape-stack']['escape-stack']Passed
call-region regression 0['call-region']['call-region']Passed
call-region regression 1['call-region']['call-region']Passed
capture-validity regression 0['capture-validity']['capture-validity']Passed
capture-validity regression 1['capture-validity']['capture-validity']Passed
packed-reference regression 0['packed-reference']['packed-reference']Passed
packed-reference regression 1['packed-reference']['packed-reference']Passed
destructor-narrowing regression 0['destructor-narrowing']['destructor-narrowing']Passed
destructor-narrowing regression 1['destructor-narrowing']['destructor-narrowing']Passed

SHA-256 / 6823edc720c300b71cd782238de2349cdea763c4b466a859b25edf3c6d6a95b5

2 / The unsuccessful fix

Exit 1
"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(d):
    errors=[]
    if not set(d['captures'])<=set(d['declared']): errors.append('capture-declaration')
    if any(a!=b and b.startswith(a+'.') for a in d['captures'] for b in d['captures']): errors.append('capture-prefix')
    if len(d['unique'])!=len(set(d['unique'])): errors.append('unique-duplicate')
    if bool(d['consumed']) and d['mode']=='Shared': errors.append('once-mode')
    if bool(d['mutated']) and d['mode']=='Shared': errors.append('mut-mode')
    if d['escapes'] and bool(set(d['captures'])&set(d['stack'])): errors.append('escape-stack')
    if not set(d['calls'])<=set(d['env']): errors.append('call-region')
    if not set(d['env'])<=set(d['valid']): errors.append('capture-validity')
    if bool(set(d['captures'])&set(d['packed'])): errors.append('packed-reference')
    if any(p.split('.')[0] in d['drop_aggregates'] for p in d['narrow_moves']): errors.append('destructor-narrowing')
    return errors
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'captures': [], 'declared': [], 'unique': [], 'consumed': [], 'mutated': [], 'mode': 'Shared', 'escapes': False, 'stack': [], 'env': [], 'calls': [], 'valid': [], 'packed': [], 'narrow_moves': [], 'drop_aggregates': []}
check('well formed empty obligations',solve(base),[])
check('capture-declaration regression 0', solve(dict(base, **({'captures':['a','b'],'declared':['a']}))), ['capture-declaration'])
check('capture-declaration regression 1', solve(dict(base, **({'captures':['a','x'+str(N)],'declared':['a']}))), ['capture-declaration'])
check('capture-prefix regression 0', solve(dict(base, **({'captures':['r','r.y'],'declared':['r','r.y']}))), ['capture-prefix'])
check('capture-prefix regression 1', solve(dict(base, **({'captures':['r','r.y.z'],'declared':['r','r.y.z']}))), ['capture-prefix'])
check('unique-duplicate regression 0', solve(dict(base, **({'unique':['r','r']}))), ['unique-duplicate'])
check('unique-duplicate regression 1', solve(dict(base, **({'unique':[N,N]}))), ['unique-duplicate'])
check('once-mode regression 0', solve(dict(base, **({'consumed':['x'],'mode':'Mut'}))), ['once-mode'])
check('once-mode regression 1', solve(dict(base, **({'consumed':list(range(N)),'mode':'Mut'}))), ['once-mode'])
check('mut-mode regression 0', solve(dict(base, **({'mutated':['x']}))), ['mut-mode'])
check('mut-mode regression 1', solve(dict(base, **({'mutated':[N]}))), ['mut-mode'])
check('escape-stack regression 0', solve(dict(base, **({'escapes':True,'captures':['a','b'],'declared':['a','b'],'stack':['b']}))), ['escape-stack'])
check('escape-stack regression 1', solve(dict(base, **({'escapes':True,'captures':['a','c'],'declared':['a','c'],'stack':['c']}))), ['escape-stack'])
check('call-region regression 0', solve(dict(base, **({'calls':[N],'env':[N+1],'valid':[N+1]}))), ['call-region'])
check('call-region regression 1', solve(dict(base, **({'calls':[N,N+1],'env':[N+1,N+2],'valid':[N+1,N+2]}))), ['call-region'])
check('capture-validity regression 0', solve(dict(base, **({'env':[N,N+1],'valid':[N]}))), ['capture-validity'])
check('capture-validity regression 1', solve(dict(base, **({'env':[N],'valid':[N+1]}))), ['capture-validity'])
check('packed-reference regression 0', solve(dict(base, **({'captures':['a','b'],'declared':['a','b'],'packed':['b']}))), ['packed-reference'])
check('packed-reference regression 1', solve(dict(base, **({'captures':['a','c'],'declared':['a','c'],'packed':['c']}))), ['packed-reference'])
check('destructor-narrowing regression 0', solve(dict(base, **({'narrow_moves':['r.f'],'drop_aggregates':['r']}))), ['destructor-narrowing'])
check('destructor-narrowing regression 1', solve(dict(base, **({'narrow_moves':['r.f.g'],'drop_aggregates':['r']}))), ['destructor-narrowing'])
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 fixtureActualExpectedOutcome
well formed empty obligations[][]Passed
capture-declaration regression 0['capture-declaration']['capture-declaration']Passed
capture-declaration regression 1['capture-declaration']['capture-declaration']Passed
capture-prefix regression 0['capture-prefix']['capture-prefix']Passed
capture-prefix regression 1['capture-prefix']['capture-prefix']Passed
unique-duplicate regression 0['unique-duplicate']['unique-duplicate']Passed
unique-duplicate regression 1['unique-duplicate']['unique-duplicate']Passed
once-mode regression 0[]['once-mode']Failed
once-mode regression 1[]['once-mode']Failed
mut-mode regression 0['mut-mode']['mut-mode']Passed
mut-mode regression 1['mut-mode']['mut-mode']Passed
escape-stack regression 0['escape-stack']['escape-stack']Passed
escape-stack regression 1['escape-stack']['escape-stack']Passed
call-region regression 0['call-region']['call-region']Passed
call-region regression 1['call-region']['call-region']Passed
capture-validity regression 0['capture-validity']['capture-validity']Passed
capture-validity regression 1['capture-validity']['capture-validity']Passed
packed-reference regression 0['packed-reference']['packed-reference']Passed
packed-reference regression 1['packed-reference']['packed-reference']Passed
destructor-narrowing regression 0['destructor-narrowing']['destructor-narrowing']Passed
destructor-narrowing regression 1['destructor-narrowing']['destructor-narrowing']Passed

SHA-256 / 50c68499c12e2b427dfc5d011043c28fa529fa043ed44c5175940f68d8a1ed6f

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 21 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

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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 2026-09-29T14:43:59.340263+00:00.

Case digest / c1e1c8ec647c21d3055ac9ff8c079acb6a21def89dc4e1579f30648d5383ed71