FAILURE MAP
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FA-43996 / Borrow checking / Open access

Unsizing manufactures a new referent allocation identity · case 01

Unsizing manufactures a new referent allocation identity.

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

ROOT CAUSE

The static analyzer mishandles unsize owner: unsizing manufactures a new referent allocation identity.

THE FAILURE

The static analyzer mishandles unsize owner: unsizing manufactures a new referent allocation identity.

Unsuccessful approach: The partial repair uses if d['source_owner'] is not None and d['target_owner'] is None: errors.append('unsize-owner'), which still violates the stipulated analysis contract.

Case contract

Check reference coercion proof steps. Unique-to-shared freeze is one-way; unsizing preserves owner; trait unsizing retains metadata; array-to-slice length equals array extent; nested mutable references cannot shorten inner lifetime; shared outer references may shorten; deref coercion records every intermediate loan; implicit coercion cannot execute a moving deref; reification of a borrowed function pointer preserves captured lifetimes; never-type branch coercion contributes no invented loan. 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['source_shared'] and d['target_unique']: errors.append('freeze-direction')
    if False: errors.append('unsize-owner')
    if d['unsized'] and not d['metadata']: errors.append('unsize-metadata')
    if d['array_coerce'] and d['array_size']!=d['slice_size']: errors.append('array-slice-extent')
    if d['nested_mut'] and d['inner_before']!=d['inner_after']: errors.append('nested-mut-invariance')
    if d['shared_outer'] and d['outer_after']>d['outer_before']: errors.append('outer-shared-shortening')
    if not set(d['intermediate'])<=set(d['recorded']): errors.append('deref-intermediates')
    if d['implicit'] and d['moving_deref']: errors.append('implicit-moving-deref')
    if not set(d['captured'])<=set(d['reified']): errors.append('function-reification-capture')
    if d['never_branch'] and bool(d['invented']): errors.append('never-no-origin')
    return errors
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'source_shared': False, 'target_unique': False, 'source_owner': None, 'target_owner': None, 'unsized': False, 'metadata': True, 'array_size': 0, 'slice_size': 0, 'array_coerce': False, 'nested_mut': False, 'inner_before': 0, 'inner_after': 0, 'shared_outer': False, 'outer_before': 0, 'outer_after': 0, 'intermediate': [], 'recorded': [], 'moving_deref': False, 'implicit': False, 'captured': [], 'reified': [], 'never_branch': False, 'invented': []}
check('well formed empty obligations',solve(base),[])
check('freeze-direction regression 0', solve(dict(base, **({'source_shared':True,'target_unique':True}))), ['freeze-direction'])
check('freeze-direction regression 1', solve(dict(base, **({'source_shared':True,'target_unique':True,'outer_before':N,'outer_after':N}))), ['freeze-direction'])
check('unsize-owner regression 0', solve(dict(base, **({'source_owner':'a','target_owner':'b'}))), ['unsize-owner'])
check('unsize-owner regression 1', solve(dict(base, **({'source_owner':N,'target_owner':N+1}))), ['unsize-owner'])
check('unsize-metadata regression 0', solve(dict(base, **({'unsized':True,'metadata':False}))), ['unsize-metadata'])
check('unsize-metadata regression 1', solve(dict(base, **({'unsized':True,'metadata':False,'outer_before':N,'outer_after':N}))), ['unsize-metadata'])
check('array-slice-extent regression 0', solve(dict(base, **({'array_coerce':True,'array_size':N+1,'slice_size':N}))), ['array-slice-extent'])
check('array-slice-extent regression 1', solve(dict(base, **({'array_coerce':True,'array_size':N+2,'slice_size':N+1}))), ['array-slice-extent'])
check('nested-mut-invariance regression 0', solve(dict(base, **({'nested_mut':True,'inner_before':N+1,'inner_after':N}))), ['nested-mut-invariance'])
check('nested-mut-invariance regression 1', solve(dict(base, **({'nested_mut':True,'inner_before':N+2,'inner_after':N+1}))), ['nested-mut-invariance'])
check('outer-shared-shortening regression 0', solve(dict(base, **({'shared_outer':True,'outer_before':N,'outer_after':N+1}))), ['outer-shared-shortening'])
check('outer-shared-shortening regression 1', solve(dict(base, **({'shared_outer':True,'outer_before':N+1,'outer_after':N+2}))), ['outer-shared-shortening'])
check('deref-intermediates regression 0', solve(dict(base, **({'intermediate':['a','b'],'recorded':['a']}))), ['deref-intermediates'])
check('deref-intermediates regression 1', solve(dict(base, **({'intermediate':list(range(N+1)),'recorded':[0]}))), ['deref-intermediates'])
check('implicit-moving-deref regression 0', solve(dict(base, **({'implicit':True,'moving_deref':True}))), ['implicit-moving-deref'])
check('implicit-moving-deref regression 1', solve(dict(base, **({'implicit':True,'moving_deref':True,'outer_before':N,'outer_after':N}))), ['implicit-moving-deref'])
check('function-reification-capture regression 0', solve(dict(base, **({'captured':['a','b'],'reified':['a']}))), ['function-reification-capture'])
check('function-reification-capture regression 1', solve(dict(base, **({'captured':[N,N+1],'reified':[N]}))), ['function-reification-capture'])
check('never-no-origin regression 0', solve(dict(base, **({'never_branch':True,'invented':['r']}))), ['never-no-origin'])
check('never-no-origin regression 1', solve(dict(base, **({'never_branch':True,'invented':[N]}))), ['never-no-origin'])
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
freeze-direction regression 0['freeze-direction']['freeze-direction']Passed
freeze-direction regression 1['freeze-direction']['freeze-direction']Passed
unsize-owner regression 0[]['unsize-owner']Failed
unsize-owner regression 1[]['unsize-owner']Failed
unsize-metadata regression 0['unsize-metadata']['unsize-metadata']Passed
unsize-metadata regression 1['unsize-metadata']['unsize-metadata']Passed
array-slice-extent regression 0['array-slice-extent']['array-slice-extent']Passed
array-slice-extent regression 1['array-slice-extent']['array-slice-extent']Passed
nested-mut-invariance regression 0['nested-mut-invariance']['nested-mut-invariance']Passed
nested-mut-invariance regression 1['nested-mut-invariance']['nested-mut-invariance']Passed
outer-shared-shortening regression 0['outer-shared-shortening']['outer-shared-shortening']Passed
outer-shared-shortening regression 1['outer-shared-shortening']['outer-shared-shortening']Passed
deref-intermediates regression 0['deref-intermediates']['deref-intermediates']Passed
deref-intermediates regression 1['deref-intermediates']['deref-intermediates']Passed
implicit-moving-deref regression 0['implicit-moving-deref']['implicit-moving-deref']Passed
implicit-moving-deref regression 1['implicit-moving-deref']['implicit-moving-deref']Passed
function-reification-capture regression 0['function-reification-capture']['function-reification-capture']Passed
function-reification-capture regression 1['function-reification-capture']['function-reification-capture']Passed
never-no-origin regression 0['never-no-origin']['never-no-origin']Passed
never-no-origin regression 1['never-no-origin']['never-no-origin']Passed

SHA-256 / e00e3e77e9405b0332a476cd5679b2dcb7e73765c360a640a341b0299fc961c2

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['source_shared'] and d['target_unique']: errors.append('freeze-direction')
    if d['source_owner'] is not None and d['target_owner'] is None: errors.append('unsize-owner')
    if d['unsized'] and not d['metadata']: errors.append('unsize-metadata')
    if d['array_coerce'] and d['array_size']!=d['slice_size']: errors.append('array-slice-extent')
    if d['nested_mut'] and d['inner_before']!=d['inner_after']: errors.append('nested-mut-invariance')
    if d['shared_outer'] and d['outer_after']>d['outer_before']: errors.append('outer-shared-shortening')
    if not set(d['intermediate'])<=set(d['recorded']): errors.append('deref-intermediates')
    if d['implicit'] and d['moving_deref']: errors.append('implicit-moving-deref')
    if not set(d['captured'])<=set(d['reified']): errors.append('function-reification-capture')
    if d['never_branch'] and bool(d['invented']): errors.append('never-no-origin')
    return errors
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
base={'source_shared': False, 'target_unique': False, 'source_owner': None, 'target_owner': None, 'unsized': False, 'metadata': True, 'array_size': 0, 'slice_size': 0, 'array_coerce': False, 'nested_mut': False, 'inner_before': 0, 'inner_after': 0, 'shared_outer': False, 'outer_before': 0, 'outer_after': 0, 'intermediate': [], 'recorded': [], 'moving_deref': False, 'implicit': False, 'captured': [], 'reified': [], 'never_branch': False, 'invented': []}
check('well formed empty obligations',solve(base),[])
check('freeze-direction regression 0', solve(dict(base, **({'source_shared':True,'target_unique':True}))), ['freeze-direction'])
check('freeze-direction regression 1', solve(dict(base, **({'source_shared':True,'target_unique':True,'outer_before':N,'outer_after':N}))), ['freeze-direction'])
check('unsize-owner regression 0', solve(dict(base, **({'source_owner':'a','target_owner':'b'}))), ['unsize-owner'])
check('unsize-owner regression 1', solve(dict(base, **({'source_owner':N,'target_owner':N+1}))), ['unsize-owner'])
check('unsize-metadata regression 0', solve(dict(base, **({'unsized':True,'metadata':False}))), ['unsize-metadata'])
check('unsize-metadata regression 1', solve(dict(base, **({'unsized':True,'metadata':False,'outer_before':N,'outer_after':N}))), ['unsize-metadata'])
check('array-slice-extent regression 0', solve(dict(base, **({'array_coerce':True,'array_size':N+1,'slice_size':N}))), ['array-slice-extent'])
check('array-slice-extent regression 1', solve(dict(base, **({'array_coerce':True,'array_size':N+2,'slice_size':N+1}))), ['array-slice-extent'])
check('nested-mut-invariance regression 0', solve(dict(base, **({'nested_mut':True,'inner_before':N+1,'inner_after':N}))), ['nested-mut-invariance'])
check('nested-mut-invariance regression 1', solve(dict(base, **({'nested_mut':True,'inner_before':N+2,'inner_after':N+1}))), ['nested-mut-invariance'])
check('outer-shared-shortening regression 0', solve(dict(base, **({'shared_outer':True,'outer_before':N,'outer_after':N+1}))), ['outer-shared-shortening'])
check('outer-shared-shortening regression 1', solve(dict(base, **({'shared_outer':True,'outer_before':N+1,'outer_after':N+2}))), ['outer-shared-shortening'])
check('deref-intermediates regression 0', solve(dict(base, **({'intermediate':['a','b'],'recorded':['a']}))), ['deref-intermediates'])
check('deref-intermediates regression 1', solve(dict(base, **({'intermediate':list(range(N+1)),'recorded':[0]}))), ['deref-intermediates'])
check('implicit-moving-deref regression 0', solve(dict(base, **({'implicit':True,'moving_deref':True}))), ['implicit-moving-deref'])
check('implicit-moving-deref regression 1', solve(dict(base, **({'implicit':True,'moving_deref':True,'outer_before':N,'outer_after':N}))), ['implicit-moving-deref'])
check('function-reification-capture regression 0', solve(dict(base, **({'captured':['a','b'],'reified':['a']}))), ['function-reification-capture'])
check('function-reification-capture regression 1', solve(dict(base, **({'captured':[N,N+1],'reified':[N]}))), ['function-reification-capture'])
check('never-no-origin regression 0', solve(dict(base, **({'never_branch':True,'invented':['r']}))), ['never-no-origin'])
check('never-no-origin regression 1', solve(dict(base, **({'never_branch':True,'invented':[N]}))), ['never-no-origin'])
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
freeze-direction regression 0['freeze-direction']['freeze-direction']Passed
freeze-direction regression 1['freeze-direction']['freeze-direction']Passed
unsize-owner regression 0[]['unsize-owner']Failed
unsize-owner regression 1[]['unsize-owner']Failed
unsize-metadata regression 0['unsize-metadata']['unsize-metadata']Passed
unsize-metadata regression 1['unsize-metadata']['unsize-metadata']Passed
array-slice-extent regression 0['array-slice-extent']['array-slice-extent']Passed
array-slice-extent regression 1['array-slice-extent']['array-slice-extent']Passed
nested-mut-invariance regression 0['nested-mut-invariance']['nested-mut-invariance']Passed
nested-mut-invariance regression 1['nested-mut-invariance']['nested-mut-invariance']Passed
outer-shared-shortening regression 0['outer-shared-shortening']['outer-shared-shortening']Passed
outer-shared-shortening regression 1['outer-shared-shortening']['outer-shared-shortening']Passed
deref-intermediates regression 0['deref-intermediates']['deref-intermediates']Passed
deref-intermediates regression 1['deref-intermediates']['deref-intermediates']Passed
implicit-moving-deref regression 0['implicit-moving-deref']['implicit-moving-deref']Passed
implicit-moving-deref regression 1['implicit-moving-deref']['implicit-moving-deref']Passed
function-reification-capture regression 0['function-reification-capture']['function-reification-capture']Passed
function-reification-capture regression 1['function-reification-capture']['function-reification-capture']Passed
never-no-origin regression 0['never-no-origin']['never-no-origin']Passed
never-no-origin regression 1['never-no-origin']['never-no-origin']Passed

SHA-256 / fd1cba08a67bd174af883747c74df0b323afe48913560a24de1b18e2f296044a

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 2026-09-29T14:44:08.129114+00:00.

Case digest / 6acaa6e37a7c3d8f4e5c4ef621530956b18fad312e2962182571d582373330b3