Elamur Groupantsvfs-error
The groupant beside vfs/src/error.rs in the Mova repository: what the code computes, what it never does, how to go back from its outputs, its invariants, cost and checks.
Facts
Implementation material. A Mova code model describes this code at one source revision: partial models, finite checks and their stated scope. It is not a reviewed general exposition, and its labels are shown as written, never raised.
Components
| component | label | where |
|---|---|---|
| approximant | partial | approximant |
| ast | partial | syntax.json |
| composition | partial | composition |
| cost | partial | Cost |
| descriptant | present | descriptant |
| invariant | partial | Invariant |
| tests | executed bounded checks | tests |
Obernants
The typed relations around the forward model: the behaviour complement (what the code never does), the reverse reconstruction (every input compatible with an output) and specialised views.
| id | type | label | where |
|---|---|---|---|
behavior_complement | behavior_complement | partial source derived model | behavior_complement |
reverse_reconstruction | reverse_reconstruction | partial source derived model | reverse_reconstruction |
errno_quotient | errno_quotient | partial source derived model | errno_quotient |
wasi_bijection | wasi_bijection | partial source derived model | wasi_bijection |
detail_precedence | detail_precedence | partial source derived model | detail_precedence |
limit_partition | limit_partition | partial source derived model | limit_partition |
Model text
descriptant
vfs-error
Errno numberings, error details and OS transport.
Prospective epoch
2026-10-31: source reviewed before edits; prospective review retained under $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31/prospective.md. Predicted order/cost: O(1) fixed23 variants/scans; O(detail bytes) owned string and display.
Observation epoch
Bounded actual calls and compiled negative controls are recorded in tests.md. Production behavior bytes unchanged; only focused test blocks added. Snapshot constant-time wording is conditional on cwd and destruction; recursive operations may partially commit.
Unsupported approximants
No executable percentage surrogate is claimed for these categorical/state/effect observations. Future 1%,2%,5%,10% require a useful metric, explicit domain and exact reference.
approximant
Forward relation
Errno numberings, error details and OS transport.
linux(Perm)=linux(NotCapable)=1; wasi distinguishes 63 and76. from_linux scans ALL excluding NotCapable; from_wasi scans all23. Display(detail)=detail, otherwise text plus Linux code. Unknown OS errno becomes Io with original display.
Domain: bounded inputs with available allocation and nonoverflowing counters unless checked explicitly. The relation is partial and source-derived.
composition
Composition
Errno numberings, error details and OS transport. Shared state and order: linux(Perm)=linux(NotCapable)=1; wasi distinguishes 63 and76. from_linux scans ALL excluding NotCapable; from_wasi scans all23. Display(detail)=detail, otherwise text plus Linux code. Unknown OS errno becomes Io with original display.
Scoped children project this same source. Their domains and effects remain conditional; source execution connects these clauses rather than independently proving their wiring. Within ALL, WASI roundtrip preserves tags; Linux roundtrip preserves all except NotCapable becomes Perm. Detail overrides tag text without changing errno.
models
Typed source models
Source-bound partial relations; no universal finite-test proof.
behavior_complement
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Under declared enum universe, WASI decoding does not map76 to Perm; known Linux2 does not become Io. Detail-bearing display cannot append automatic OS suffix.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
reverse_reconstruction
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Linux code1 has compatible tags {Perm,NotCapable}; from_linux chooses Perm. Display with arbitrary detail cannot reconstruct errno or OS cause; recognized WASI codes recover exactly one tag.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
errno_quotient
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: Linux transport forms one non-singleton fiber {Perm,NotCapable}; this is intentional information loss, not inverse equality.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
wasi_bijection
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: On 23 emitted u16 codes, from_wasi(wasi(e))=Some(e); unknown code has None.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
detail_precedence
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: FsError{errno,Some(d)} displays d even when empty; default text depends on errno only when None.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
limit_partition
Subject: vfs-error. Domain: Errno numberings, error details and OS transport. Valid allocations, bounded counters, Fault=None unless explicitly named. Observation: one call or the stated finite trace.
Operator: is_limit true exactly for FBig,NoSpc,DQuot; root escape belongs to denied category instead.
Approximation: source-derived partial relation; complement is an inner excluded-behavior claim under these premises, converse retains compatible antecedents. Evidence: tests.md; unobserved concurrency/resource failures remain unknown.
tests
Checks and limitations
Exact named observations: error::wave31::errno_fibers_and_display.
Fresh receipts: $MOVA_DATA/runs/octopus-wave31-vfs-2026-10-31; run.sh retains four profile/repetition sets with raw logs and numeric statuses. native-commands.json and source-test-map.json disambiguate targets. Compiled mutations and exact restoration are separately retained in mutation-summary.json.
These finite observations are not semantic completeness. Source syntax generated twice and compared byte-for-byte. Host effects are limited to owned TMPDIR fixtures. Existing absolute_paths_never_reach_the_host and open_modes are skipped; snapbench main is skipped. Standalone helpers/reexports are only observed through named callers or representation checks; RealFs effect methods unexecuted.
invariant-and-cost
Invariant and cost
Invariant
Within ALL, WASI roundtrip preserves tags; Linux roundtrip preserves all except NotCapable becomes Perm. Detail overrides tag text without changing errno.
Cost
O(1) fixed23 variants/scans; O(detail bytes) owned string and display.
No timing or numerical error guarantee is inferred from finite tests.
This page in Markdown → https://md.groupants.elamur.ai/free/en/mova/vfs/src/error.rs.groupant/