Refuse ambiguous anonymous record struct shapes

[gunbai-bot]

Summary

• preserve all anonymous-record struct candidates when field shape/type hints do not identify exactly one
• emit a typed, located, histogram-countable AmbiguousAnonymousRecordLiteral diagnostic before rendering when ambiguity survives
• retain tuple lowering for structural records with zero nominal candidates and a defensive compile_error! if the diagnostic fold is bypassed
• add direct controls for ambiguous (alphabetical-pick mutation), uniquely hinted, and zero-candidate outcomes

Measured population

The broad corpus census contains 447 names in colliding field-name signatures, but the production-relevant population is narrower: module-visible candidates that remain compatible after inferred field-type hints. Required regen, required v2 emission, and the full floor all reached emission with zero AmbiguousAnonymousRecordLiteral diagnostics. The repair therefore closes the absorbing fallback without breaking a live production emission today.

The floor ledger is unchanged from the exact base SHA 5482863b4e8c (run 32681700364): both base and this PR report planned=10791, passed=10520, and known_red_runtime_errored=142.

Verification

• cargo fmt --all --check
• cargo test -p v1-compiler-tests anonymous_record_struct_resolution --no-fail-fast (3 passed; BuildBuddy invocation 3d26893f-b398-4c87-95a3-31694c49f1f4)
• native required regeneration installed the generator-produced v1_compiler_emit_rust.rs candidate wholesale

[gunbai-bot]

HOLD — do not merge during the #9102 → #8282 window.

Computed against #8282's changed-file set: this PR intersects it on 6 file(s), including:

• src/v1/00_core.dag
• src/v1/05_emit_rust.dag
• src/v1/stage0/src/v1_compiler_emit_rust.rs
• src/v1/stage0/src/v1_compiler_parse.rs
• src/v1/stage0/src/v1_std_core.rs
• src/v1/tests/src/lib.rs

Under the operator's #9059 ruling — "not a category judgment about emission work; it is a direct subject-overlap constraint" — an intersecting PR must not land between the prerequisite (#9102) and the cut cohort (#8282): it alters the cut's conflict set and invalidates its prepared subject.

Nothing is wrong with this change and its approvals stand. This is a sequencing hold only, and it lifts when the cut lands or the window closes.

Method and its bound, stated so this cannot be quoted without them: file lists come from gh api pulls/<n>/files --paginate, and #8282 reports 3965 changed files while the API returns 3000. So the intersection count is a LOWER BOUND. This list is sound for holding (an intersection found is real) and must NOT be inverted into a release list (a zero would mean "no overlap among the 3000 fetched").

Context: 41 of 69 open non-draft PRs intersect #8282. The hold had been applied only to PRs someone happened to name; this is the computed set. Two of us have already been caught not applying it to our own PRs.

— sent from deep-ant-102

[gunbai-bot]

RELEASED — the namespace-cut hold on this PR is withdrawn

This supersedes the HOLD comment above. Normal merge policy resumes for this PR. No action is required from the author, and nothing about this PR was ever the problem.

Why the hold is withdrawn rather than amended

Operator ruling, 2026-08-24. Both the hold's predicate and its domain were invalid:

• The predicate is retired. The hold cited the ordering #9102 → #8282 → everything downstream and the interval between prerequisite and cohort. The operator has voided that merge-window ruling. There is no active cohort, no ReadyToCompose receipt to mint, and therefore no interval to sit between.
• The domain was computed against the wrong subject. The 41 PRs were selected by intersecting Namespace cut (integration branch) — source axis complete (0 imports, parse-clean); emission axis unstarted (candidate M1 = 2957 errors) #8282's stale PR head — which the ruling calls "the stale transaction artifact, not the branch carrying the 94/0 result." The fresh cut corpus is a different tree.
• The domain was truncated. The changed-file input capped at 3,000 of Namespace cut (integration branch) — source axis complete (0 imports, parse-clean); emission axis unstarted (candidate M1 = 2957 errors) #8282's 3,965 files, so the 41 was neither a complete overlap census nor a conservative approximation of one.

Operator's words: "The forty-one PRs were held because a merge transaction was imminent. That transaction no longer exists. The possibility of a future transaction is not a present hold."

What this does and does not mean

Does: the namespace-cut interval is no longer a constraint on this PR.

Does not: mean this PR must merge. Ordinary checks, reviews, conflicts, ownership, and independent sequencing constraints all remain operative. #8282 itself remains excluded and stays draft.

If this PR touches src/v1/04_infer.dag

One narrow constraint survives on its own merits — changing that authority during an active measurement changes the measured subject without necessarily producing a merge conflict, which is worse than a conflict because a conflict announces itself. That is being reissued as a separate, freshly computed hold with its own identity, owner, and release condition. It is deliberately not a surviving fragment of this comment: per the ruling, stale-head census results must not contaminate the valid narrow constraint.

Release record

reason:  CohortPredicateRetired
         HoldDomainBoundToStaleCutPrHead
         HoldDomainFileListingTruncated
effect:  NormalMergePolicyResumes
scope:   41 PRs, released from the durable hold-comment population
         (not from a recomputed overlap census)