NOVA

A constraint-native programming language — research preview

Purity by default. Authority as an unforgeable token. Effects in the type.

Quickstart • The idea • What actually works • Roadmap • Contributing

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Status

NOVA is an early research preview (0.2). What exists and is tested is a frontend and a reference interpreter: a lexer, parser, Hindley–Milner type inference, row-typed effect checking, capability-reachability analysis, and a tree-walking evaluator that runs checked programs. There is also a native C backend for a first-order subset of the language, and regionlab, a separate prototype for the region-based memory model.

Everything else the design documents describe — the distributed runtime, the reactive WASM frontend, autonomous-agent governance, a package registry, self-hosting — is design, not implementation. See ROADMAP.md for what is gated on what, and docs/known-issues.md for every gap we know about, recorded honestly per Constitution Article XII.

The version is 0.2 deliberately: Article XII forbids claiming 1.0 before the core is frozen, the specification is complete, and two independent implementations agree. Currently there is one implementation.

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The idea

Programs carry real-world obligations that mainstream languages cannot express in a signature:

• This dependency must not touch the network.
• This closure must not smuggle out filesystem authority it captured.
• This function's side effects must be visible to its caller.

Today those obligations live in code-review comments, linter configs and runtime sandboxes — checked late, by tools that do not understand whole-program semantics. NOVA puts them in the type system:

1. Pure by default. What a function does is part of its signature: fn f(rt: Runtime) -> Int ! {Runtime}.
2. Object capabilities. Authority over the outside world is an unforgeable lexical token you must be handed. No import confers it.
3. No authority laundering. A closure that captures a capability carries it in its type; it cannot be passed somewhere that expects a pure function.

fn main(rt: Runtime) -> Int ! {Runtime} {
    rt.print("hello from NOVA");
    0
}

The diagnostic that motivates it

Capability-safe languages control who can obtain authority but lose track of it once it is captured in a closure. Effect-typed languages track what happened but allow ambient effects. NOVA rejects authority laundering statically:

fn sneaky(c: Clock) -> (() -> Int) {
    || c.now()
}

error[E0203]: closure captures capability `Clock` but its expected type
              does not declare it
 --> sneaky.nova:2:5
  |
2 |     || c.now()
  |     ^^^^^^^^^^ this closure has type `() -> Int ! {Clock}`
  = note: captures `c: Clock`
  = note: expected `() -> Int`
  = note: passing it here would hide the effect `Clock` from callers

This is real; it is tests/conformance/004-closure-cannot-launder-authority.nova.

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Quickstart

Requires Python 3.10+ and, for nova build, clang.

git clone https://github.com/ieeecsopen/NOVA.git
cd NOVA

# Run the full verification suite (what CI runs)
./tools/check-all.sh

# Type- and effect-check a program
./nova check examples/hello.nova

# Run it (reference interpreter — the authoritative engine)
./nova run examples/hello.nova

# Build an executable artifact
./nova build examples/hello.nova && ./hello

nova build produces a native binary when the program stays inside the subset the C backend supports (top-level functions, Int / Bool / String / struct, Runtime / Clock), and otherwise an interpreter-backed runner — a real runnable artifact that executes through the reference interpreter. It tells you which, and it never emits a binary it cannot compile.

# Scaffold a project
./nova new my_service && cd my_service && ../nova check

# Inspect intermediate representations (informational)
./nova check examples/hello.nova --emit-hir --emit-mir

Editor support

cd editors/vscode && npm install && npm run package

produces nova-lang-<version>.vsix — syntax highlighting, live diagnostics (via nova lsp), completion, and NOVA: Check / Run / Build commands. Set nova.toolchainPath to the repo's nova script if it is not on your PATH.

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What actually works today

Area	State
Lexer, parser, spans, diagnostics	Working, verifier/refspec/
Hindley–Milner type inference	Working
Row-typed effect checking (equality, not subsumption)	Working
Capability model + laundering prevention (closures and struct fields)	Working
Structs, enums, tuples, pattern matching, exhaustiveness	Working
Generics, traits, impl	Working (limits: known-issues P1–P2)
Modules, visibility	Working (flat namespace: known-issues P3)
Local mutability, while, for over List	Working
Prelude capabilities: Runtime, Clock, Filesystem, Network	Working in the interpreter
Reference interpreter	Working, authoritative
Native C backend	First-order subset only (known-issues C1)
Language server (nova lsp)	Minimal — diagnostics, completion, formatting
VS Code extension	Working — editors/vscode/, builds to a .vsix
regionlab region/ownership checker	Prototype, separate, regionlab/
HIR / MIR	Informational scaffolding (known-issues C2)
Package registry, attenuate, string ops, WASM Component Model	Not implemented
Distributed runtime, WASM UI, AI-agent governance, concurrency runtime	Design only — see ROADMAP.md

The 50-test conformance suite (tests/conformance/) is the shared arbiter for the semantics; it includes explicit attack cases (return a capability, stash it in a let-bound closure, hide an effect in one match arm).

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Compiler pipeline

NOVA source (.nova)
  │  verifier/refspec/   — the authoritative frontend
  ▼
Lexer → Parser → AST (spans + node ids)
  → name & module resolution (RFC 0004)
  → Hindley–Milner type inference (RFC 0001)
  → row-typed effect checking (RFC 0001 §4.3 — equality, `= widen` to opt into subsumption)
  → capability reachability (RFC 0001 §4.5 — zero ambient authority)
  │
  ├─► nova check   — stop, report diagnostics
  ├─► nova run     — reference interpreter (verifier/refspec/eval.py)
  └─► nova build   — native C for the supported subset, else an
                      interpreter-backed runner

regionlab/ implements the Region XOR memory model (Shared Read XOR Exclusive Write) as a standalone prototype with its own 14-test suite. It is not yet integrated into the main pipeline — that integration is Milestone 1.

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Benchmarks

benchmarks/ contains a wall-clock harness for the toolchain (challenge_suite.py: nova build / nova run timings on this machine) and a Python micro-benchmark of the host's own threading primitives (concurrency_bench.py).

These are not a cross-language comparison, and there is no honest one to make yet — the constructs you would compare (tasks, channels, native loops) do not have a native code path. Any earlier table pitting NOVA against Rust / Go / C++ was removed. See benchmarks/README.md.

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Roadmap

NOVA is at Milestone 0 → 1 on a milestone ladder with no dates (ROADMAP.md). In brief:

• M0 Foundation (current) — freeze the frontend semantics; resolve the open effect-derivation questions (known-issues S1, S2).
• M1 Memory discipline — integrate regionlab into the checker.
• M2 Abstraction — package manager, attenuate, qualified imports.
• M3 Compilation — a real IR and a full native backend; WASM.
• M4+ Concurrency, resources, contracts — built on the memory model, not bolted beside it.

The "platform" documents under docs/full-stack/, docs/distributed/ and docs/ai/ are the deferred agenda (M7+). They are kept because the thinking is load-bearing, not because the code exists.

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Documentation

Category	Documents
Foundation	Constitution • Philosophy • Program Model • Non-Goals • Decision Log • Authority Map • Epic implementation status
Language	Syntax & Grammar • Syntax Cheatsheet • Type System • Effect System • Capabilities • Memory Model
RFCs	0001 core • 0002 data types • 0003 generics/traits • 0004 modules • 0005 mutability • 0006 ownership/borrowing
Honesty	Known issues • Roadmap
Deferred agenda (design only)	Runtime • Full-stack • Distributed • AI governance • Platform
Open source	Contributing • Contributor Roadmap • Issue Backlog

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Contributing

# Verify local changes before a PR
./tools/check-all.sh

Read CONTRIBUTING.md and the Constitution. Good first work right now is in the frontend and the conformance suite — the areas that are real. See docs/known-issues.md for concrete, scoped problems.

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License & governance

Apache 2.0 (LICENSE). Governance in GOVERNANCE.md; security reporting in SECURITY.md.