rs-0.3.0#

Rust bootstrap compiler release, 2026-09-18. Backend: JavaScript running on Node.

Core language and runtime#

• Structured expressions and lexical scope resolution: bare assignment updates the nearest existing binding; annotations and cold explicitly declare locals.
• Runtime type checks, checked signed 32/64-bit integers, noncoercing equality, identity-based container equality, and boolean short-circuiting.
• Fixed bindings, recursive container immutability through aliases, mutable deep .copy() with cycle/shared-reference preservation, and hot constant substitution.
• while, iterable and three-part for, break, and continue; snapshot iteration.
• Working array/set/pair APIs and insertion-ordered map()/dict() with null for missing keys, inspection methods, and typed collection mutation checks.

Unicode strings and slicing#

String length, iteration, reversal, and slicing count extended grapheme clusters. Combining marks and joined emoji stay together. Node must provide Intl.Segmenter. String .reverse() returns a new string without changing the original.

String and array .slice(start,end) and .lenslice(start,length) accept an optional third boolean argument, including the slicing-only reverse=true form. Reverse slicing counts from the end and preserves the original order:

func m{
    out("ABCDE".lenslice(0,3,reverse=true)); // CDE
}

Invalid bounds raise OutOfBoundsError. Zero-length slices are valid at the end. Incorrect argument types or counts raise TypeError.

Fixes and migration notes#

The bundled example now executes successfully. Regressions addressed include repeated assignment, comparisons mistaken for declarations, comment markers in strings, compact blocks, compound me expressions, and shadowed built-ins.

Explicit redeclarations in the same scope and undefined names are rejected. Programs relying on accidental JavaScript coercion or out-of-range array slicing must be updated. Array slices now use strict bounds rather than silently clipping or accepting negative indices. Array reversal still mutates the array.

Comma-separated function parameters from rs-0.2.0 remain required.

Documentation and validation#

The API reference covers syntax, strings, collections, built-ins, and errors, with a runnable example. Discussion documents are removed from the tracked tree and remain local; docs/api/ and docs/releases/ are exempt from the documentation ignore rule.

Validation: cargo test passes 55 tests (7 unit and 48 integration), none ignored. Execution tests run generated JavaScript under Node and cover the API example.

Remaining limitations#

Self-hosting, a unified lexer/parser with source locations, complete modules and exports, standard-library packages, decorators, deque, async, match, and run/handle/then remain pending. General named arguments are deferred. Unicode segmentation follows the host's Unicode/ICU version. The compiler still targets Node rather than a native runtime.