Faber 1.10.0

Install this version#

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Release notes#

Status: draft

Faber 1.10 continues the 1.x development line. Since 1.9.0, the language adds type algebra and heritage, Cartesian range products, lockstep collection walks, decimal widths, conversion enrollment, kernel closures, and per-file reader locales. Tooling adds execution statistics, stronger generated-Rust validation, and more honest target checks. This draft covers the 26 August through 2 September 2026 candidate window; version files remain labeled 1.9.0 until the release commit.

Language#

Type algebra and heritage. ∩ and ∪ are checked type operators. In the English reader, abstract, extends, and implements are checked language forms; the Latin spellings are abstractus, sub, and implements. They are semantic relations, not comments. The English trap capture boundary (trap in Latin) reifies a failable result alongside declared ⇥ channels and local handlers. expect_failure (expect_failure in Latin) now has strict behavior: a case that unexpectedly succeeds is rejected.

N-ary iteration. for range a‥b, c‥d (for range in Latin) walks the Cartesian product of its ranges. for from xs, ys (for from in Latin) walks several collections in lockstep, with one binder per source.

Decimals. d32 and d64 are scaled-decimal width markers. Arithmetic uses scaled integer carriers with round-half-even arithmetic. d32 widens to d64; the reverse narrowing is rejected. Integer literals are rejected in a decimal context; write a decimal literal or use an explicit conversion.

Conversions (breaking). In-union @ conversion (@ conversion in Latin) arms are gone. Conversions are standalone annotated functions enrolled in one table: at most one conversion is allowed per ordered type pair per scope, builtins cannot be shadowed, and failure channels compose.

Guards. reject (reject in Latin) is the boolean opposite of require (require).

Match and narrowing. match (match in Latin) cases use type patterns with case (case in Latin) and bind narrowed values. Narrowing persists across control flow instead of ending at the if arm.

Annotations. Bare declaration annotations must end their line before the declaration they annotate. Braced annotations remain available for same-line use.

Lista. all / any (all / any in Latin) are predicate twins on list.

Kernel closures. kernel (kernel in Latin) marks a capture-free, device-safe closure inside a host function. It is not a first-class host value or a public launch entry. Declaration annotations @ kernel / @ kernel keep their existing role; only public annotated functions are launchable device entries.

Locale. Each source file selects its own reader locale. faber format fails closed when the required reader pack is unavailable. Packs for ar, en, hi, la, th-TH, vi, zh-Hans, and zh-Hant ship embedded in the binary.

Complexity. faber check warns when a function exceeds the default cyclomatic budget of 12. Override it with --complexity-budget or the [check] complexity-budget manifest key; the CLI value wins over the manifest value, which wins over the default.

Tooling#

• faber run --stats and --stats-file write execution-statistics JSON for package runs. Device routes refuse statistics requests rather than emitting a partial artifact.
• Generated Rust is held to compile-clean output for supported members, while broader emitter-shape cleanup continues. The Rust e2e harness now places its host module after crate attributes, so real lint and build stages run. The Swift e2e lint path invokes swiftc -typecheck with the accepted flag.
• Target e2e lanes now register expected failures by family instead of hiding them behind an early harness failure.
• Generic size parameters (size) forward caller witnesses to callees, allowing declared [T, D] shapes to materialize through specialization.
• The compiler workspace is now Rust edition 2024.
• Locked release builds remap private workspace and Cargo-registry paths, and the release gate scans the binary for leakage before continuing.
• The release manifest's hosts input and lockfile are refreshed together.
• Canonical Rust validation keeps its hard floor while recording only the intentional generated-artifact lint families never_loop, eq_op, and approx_constant as receipted debt. Other clippy failures remain errors.

GPU#

Staged composed matmuls, destination provenance, and plan-admission validation landed on the Metal inference path. Reverse-mode VJPs for RMSNorm and RoPE are available. Gather reverse-mode remains a known-red path (see Known issues). Metal-versus-llama.cpp parity measurement provides a baseline; closing the remaining speed gap is outside this release.

Breaking changes#

1. In-union @ conversion (@ conversion in Latin) arms are rejected. Rewrite them as standalone annotated conversion functions.
2. Same-line bare declaration annotations are rejected. Put the declaration on the following line, or use a braced annotation.
3. Integer literals in decimal contexts are rejected.
4. d64 to d32 decimal narrowing is rejected.
5. Only public @ kernel / @ kernel functions are launchable device entries. A private declaration annotation is not a public entry.

Known issues#

• The browser-product build check remains red because generated TypeScript still misses __faberValorTag on Identity.
• The Gather reverse-mode VJP check remains red on the repeated-index path; a required indexed scatter-add AIR primitive is still reported there.
• The Gradus cache package check reports a live LOCALE002 near-keyword warning where its expectation records SEM002. This is diagnostic-code drift, not a cache failure.
• Thirteen environment-gated checks remain skipped: nine device-artifact/export gates and four prefill-oracle gates requiring GEA_SOURCE or GEA2_F32_GGUF.
• Two package checks remain unavailable when the optional Triga provider is absent; they report PKG001 for the missing triga:math provider.

Not in this release#

• The larger collection-ergonomics rewrite remains outside this release and is still in design and admission.
• Type-algebra corpus conversion, remaining generated-Rust shape cleanup, and later kernel-closure units continue after 1.10.
• Tensor-glyph law text, set-algebra glyphs, and container-bounds folding remain open or deferred.
• Cista remains on the 0.1.0 line.
• Haskell and Python remain source-emit surfaces. Cross-module string handles and numeric-inference accuracy are unchanged claims.
• The AMDGPU lane remains a limited discovery-first surface and requires ROCm clang for compilation.
• Decimal widening from non-Rust call sources remains fail-closed.

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