typhon

Typhon — Language, Compiler, Runtime, and VM Skill

Typhon is a statically-typed, stricter superset of Python that emits clean CPython 3.13+ with zero runtime dependency on the toolchain. The compiler, language server, formatter, debugger wrapper, REPL, and tree-walking interpreter are all a single Rust binary called tyc. Every .ty file emits valid, idiomatic .py. Not all .py is valid Typhon.

Current release: v1.0.0-alpha.6 (2026-07-21) — a maintenance release on top of alpha.5, driven by the 2026-07-20 release-readiness review (docs/release-readiness-2026-07-20.md). The July dependency wave is carried safely across the toml 0.8 → 1.x major — including the fix, before it could ship, for the one regression that bump introduced (the tyc-venv dependency allow-list reader silently returning empty, which would have no-opped third-party arg/type checking). Six squashed-acronym keywords join the secret-name table (API_TOKEN, APITOKEN, API_SECRET, APISECRET, API_PASSWORD, APIPASSWORD), now hoisted into a single shared tyc_analyse::SECRET_NAME_KEYWORDS constant so the tyc::contains_secret_literal lint and the tyc build scan can no longer drift. The release pipeline's artifact download is re-pinned to the proven v4 line (matching the v4 upload), and docs-site accessibility, diagnostics-index completeness (all 87 pages indexed), and repo hygiene (the .Jules/.jules case-collision fix) round it out. No new syntax; no previously-correct program changes behaviour — the only diagnostic-surface change is warn-level (six more secret-shaped names warned). v1.0.0-alpha.5 (2026-07-09) was a performance-focused release on top of alpha.4. VM performance Tier 1 (tyc run): a two-representation VmInt (Small(i64) inline, Big(BigInt) on overflow) keeps common-path integer arithmetic allocation-free while preserving CPython's exact arbitrary-precision semantics; a per-class resolved-method cache (negative results included) and a direct obj.method(args) dispatch path skip redundant find_method walks and BoundMethod allocation; and functions with no closures/global/nonlocal resolve locals to a fixed slot computed once instead of a HashMap lookup per read/write. Cumulative effect: the VM's steady-state slowdown vs tyc build + CPython compresses from ~5–18× to ~3–14× (startup-adjusted); the VM still wins on startup latency. [optimise] config profile + tyc build -O: a single level dial flips the default of auto-memoise / auto-gather / auto-parallel / pgo-memoise to true (an explicit [strictness] entry always wins). Seven new advice-only lints in tyc-analyse/src/perf.rs, gated by [strictness] suggest-perf: perf_membership_in_loop, perf_list_shift_in_loop, perf_str_concat_in_loop, perf_sort_in_loop, perf_sorted_first, perf_keys_membership, and lazy_import_opportunity. Free-threading parallelisation wave ([python] free-threaded = true): auto-parallel widens to comprehension filters, multi-argument calls, and nested pure calls; a new auto-parallel-reductions knob folds a provably-bounded integer accumulator loop (mut total: int; for x in xs: total += EXPR) into a parallel sum(map_pure(...)); two new advice lints (parallel_opportunity, shared_mut_across_tasks); and a parallel-backend = "interpreters" option tries a PEP 734 InterpreterPoolExecutor before falling back to threads. Native PEP 810 lazy imports: [python] target = "3.15" / "3.15t" lowers lazy import ALIAS = MODULE to CPython's native lazy import MODULE as ALIAS statement instead of the typhon_runtime helper call; 3.13/3.14 output is byte-for-byte unchanged. No new syntax; every rewrite here is opt-in or advice-only, so no previously-correct program changes behaviour. v1.0.0-alpha.4 (2026-07-08) was a focused hardening pass on top of alpha.3. Type-checker soundness: it closes H5, the one HIGH finding the release-readiness review deferred — the v0.15.0 qualified↔bare tail-unification let a locally declared class satisfy a same-named class from another module (a user class Response: type-checked into an httpx.Response-typed slot, and vice versa). is_assignable now refuses that unification when the bare side names a class declared in the module being checked and the qualified side's declaration — resolved through its exact module key — has a different shape. The guard is evidence-gated and degrades to the previous permissive unification on any uncertainty (unresolvable module, unknown shape, facade re-export with an equivalent shape, interfaces, bare names of unknown provenance), so the example/stress corpus is byte-identically unchanged. Diagnostics: the secret-name keyword tables in tyc-analyse and the tyc build scan match longest-first again — APIKEY precedes the bare KEY, so KEY_APIKEY reports the more-specific suffix. Supply-chain & packaging: every third-party GitHub Action is SHA-pinned (Dependabot keeps the pins fresh), the installers resolve the newest release including pre-releases (a default install no longer silently fetches older binaries), and a round of dependency / advisory bumps lands (crossbeam-epoch 0.9.20 for RUSTSEC-2026-0204, plus regex, memchr, compact_str). No new syntax; like the alpha.2 diagnostics, the H5 fix is a conservative narrowing that only rejects programs passing a provably-different-shaped class across a module boundary, so no previously-correct program changes behaviour. v1.0.0-alpha.3 (2026-07-03) was a release-readiness remediation pass (RELEASE_READINESS_REVIEW.md), the licensing / packaging / robustness counterpart to alpha.2's soundness sweep. Licensing & packaging: a repository-root MIT LICENSE, the upstream Ruff MIT notice vendored beside the fork, SECURITY.md / CONTRIBUTING.md / Dependabot, and release-workflow hygiene (pre-release tags flagged as such; auto-tag gated on green CI). Compiler & VM: identical errors at distinct source locations are all reported now (the module- and resolver-level dedupe no longer swallows the 2nd+ occurrence), nested-generic assignability is linear again (not O(2^depth)), four more flow-narrowing invalidation holes are closed, and six VM↔CPython parity gaps are fixed (cyclic-value comparison no longer aborts the process, str.find/rfind/index/rindex return character offsets, in-place list +=, float %/// sign & zero-division, broken-pipe print, json.dumps scalar-key coercion). Tooling: a 256 MiB LSP stack, atomic tyc fmt (temp-file + rename), a TYC_NO_INTROSPECT kill-switch for venv dependency introspection, Windows venv discovery, and the now-wired [strictness] exhaustive-match knob (previously a validated no-op). Diagnostics/docs: diagnostic doc URLs now point at resolvable GitHub paths (github.com/CodeHalwell/Typhon/blob/main/docs/diagnostics/<code>.md, not the never-deployed typhon.dev), and four diagnostics gained doc pages + tyc explain entries (empty_collection_no_annotation, freeze_not_freezable, newtype_invalid_base, typing_alias_in_annotation). No new syntax; the four flow-narrowing fixes are conservative widenings that only affect programs relying on a previously-unsound narrowing, so no previously-correct program changes behaviour. v1.0.0-alpha.2 (2026-06-29) was the remediation of a 2026-06-28 adversarial pre-release review: a type-checker soundness sweep (flow narrowing of a non-local place — global / instance field — is now invalidated across an intervening call or alias write; short-circuit and/or narrowing no longer false-positives on x is not None and x.method()), a batch of newly-typed positions (slice reads, subscript assignments, for / let tuple-unpack targets, match star / or-pattern captures, walrus bindings, parameter defaults), VM↔CPython parity fixes (bytes %-formatting, numeric int/float/bool dict-key collapse, VM as! enforcement), three new conservative diagnostics (tyc::not_a_context_manager, tyc::raise_non_exception, tyc::frozen_inheritance_conflict — each fires only where the emitted Python already crashed), and config / crash robustness (typhon.toml rejects unknown keys / invalid [checker] external / [strictness] severities; the CLI runs on a 256 MiB worker stack). No new syntax, and no previously-correct program changes behaviour — but, unlike the purely-additive releases before it, the three new diagnostics do narrow the accepted surface for programs that already crashed at runtime (they now surface as build-time errors instead). v1.0.0-alpha (2026-06-22) was Typhon's first tagged alpha and first feature-complete milestone: the proven surface plus the landed type-system frontier (HKT unification, user-generic variance inference, the inter-procedural field-init audit). The prior numbered release was v0.15.7 (2026-06-21). The language is additive across the v0.3.0 → v1.0.0-alpha line — every previously-accepted program continues to type-check identically (v1.0.0-alpha.2 was the first exception: its three conservative diagnostics reject a small set of programs that only ever crashed at runtime; v1.0.0-alpha.3 and v1.0.0-alpha.4 stay additive on correct programs — alpha.3's flow-narrowing fixes and alpha.4's H5 class-unification fix only reject code that relied on a previously-unsound narrowing). The v0.10.0 → v0.13.x line is dominated by two themes: making the in-process VM a true drop-in for tyc build && python, and deepening compile-time type-checking of third-party code. v0.13.0 folds in a post-release code review that fixed ten correctness issues (two VM/CPython divergences — seeded random.sample, and @staticmethod/@classmethod binding self when read through an instance — and an incompatible_override false positive on valid LSP-widening overrides); v0.13.1 is a six-fix patch from a playground stress round (async-? missing_await, `

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