Compiling a project with rsc

How to set up any Rust project to compile under the rs edition compiler.

Prerequisites

Build rsc from the rs repo:

cd ~/git/rs/rsc
cargo build --release

The binary is at ~/git/rs/rsc/target/release/rsc.

Building your project with rsc

$env.RUSTC = ($env.HOME + "/git/rs/rsc/target/release/rsc")
$env.RUSTFLAGS = "--rs-edition"
cd ~/git/your-project
cargo build

Without --rs-edition, only attribute-triggered lints run (#[deterministic], #[step], #[derive(Addressed)]). With --rs-edition, edition restriction lints (RS501–RS507) activate.

Edition restrictions (RS501–RS507)

Every violation must be fixed — not suppressed — unless interfacing with an external Rust crate.

code	forbidden	replacement
RS501	Box::new()	stack values or Arena<T, N>
RS502	Vec<T>	BoundedVec<T, N> with compile-time capacity
RS503	String	&str or ArrayString<N>
RS504	dyn Trait	generics or enum dispatch
RS505	Arc<T>, Rc<T>	cell-owned state or bounded channels
RS506	panic!()	Result for recoverable, abort for unrecoverable
RS507	HashMap, HashSet	BTreeMap, BTreeSet, or BoundedMap<K,V,N>

Fixing violations

When rsc reports errors, apply these patterns:

// RS501: Box::new(x) → stack value or arena
let node = arena.alloc(TreeNode { ... })?;

// RS502: Vec<T> → BoundedVec<T, N>
let items: BoundedVec<Item, 1024> = BoundedVec::new();

// RS502: vec.collect() → bounded collect
let result: BoundedVec<_, 256> = iter.try_collect()?;

// RS503: String → ArrayString or &str
let name: ArrayString<64> = ArrayString::try_from("hello")?;

// RS507: HashMap<K,V> → BTreeMap<K,V> or BoundedMap<K,V,N>
let lookup: BTreeMap<Key, Value> = BTreeMap::new();

Opt-in for external crate boundaries

When wrapping an external Rust crate that uses heap types internally, opt in at module or function scope:

#[allow(rs::heap)]             // lifts RS501, RS502, RS503, RS505
#[allow(rs::dyn_dispatch)]     // lifts RS504
#[allow(rs::nondeterministic)] // lifts RS507
// RS506 (panic) has no opt-out — always enforced

Never apply at crate level.

rs-lang types

Add rs-lang as a dependency and import the prelude:

use rs_lang::prelude::*;

Available types:

• BoundedVec<T, N> — fixed-capacity vec, try_push() returns Err if full
• BoundedMap<K, V, N> — fixed-capacity ordered map
• ArrayString<N> — fixed-capacity string
• Arena<T, N> — typed arena, compile-time max, all freed on drop
• FixedPoint<u128, DECIMALS> — deterministic decimal arithmetic
• Particle — 64-byte content-address hash (Copy, Eq, Ord)

CLAUDE.md template for companion projects

Add this section to the CLAUDE.md of any project compiled with rsc:

# rs-lang companion repo

this project is compiled with `rsc` — the rs edition compiler.
source of truth for the language spec lives in `~/git/rs/reference/`.

## companion repos

| repo | path | role |
|------|------|------|
| rs | `~/git/rs/` | compiler driver (rsc), proc-macros, core runtime types |
| this project | `~/git/<name>/` | application — must compile clean under rsc |

## building with rsc

\```nu
$env.RUSTC = ($env.HOME + "/git/rs/rsc/target/release/rsc")
$env.RUSTFLAGS = "--rs-edition"
cargo build
\```

rebuild rsc after any changes to `~/git/rs/rsc/`:

\```nu
cd ~/git/rs/rsc; cargo build --release
\```

## do not touch zones

- `~/git/rs/reference/` — canonical spec, change there first
- `~/git/rs/rsc/` — compiler driver, changes require rsc rebuild