velt-lang/velt

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Velt: a modern TypeScript without the funky stuff inherited from JavaScript, compiled to native code with Rust-level performance

Is velt-lang/velt beginner-friendly?

In the last 30 days, velt-lang/velt merged 175 of 180 pull requests from outside contributors, and its maintainers usually reply within 1 day. No beginner-friendly issue is open right now; the list below has the other issues we hold for it.

Stars: 0
Forks: 0
Open beginner issues: 0
Indexed issues: 151
Avg merge: 4h 1m
Merged PRs (30d): 175

Dominant language: Rust
License: Apache-2.0
Last GitHub push: Oct 5, 2026
Latest indexed: Oct 6, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: good first issue

How to contribute to velt-lang/velt

Read the contributing guide first: it says how the maintainers want changes proposed, tested and reviewed.
Read its code of conduct: it covers issues and pull requests as well as chat.
Your contributions will be published under the project's Apache-2.0 license.
Follow the repository to hear when a new beginner-friendly issue opens, or look through the other issues below.

Beginner friendly Everything

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Issues somebody may already be working on are listed last. List everything by date

Use after free: a callback that grows its array through an alias (forEach, sort, …) leaves its element arguments dangling
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- Is something wrong?
area:runtime area:std kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#564 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
opt: fuse Map get/add/set patterns in VIR
Open
- Is something wrong?
Difficulty 5/5 Over a week Newbie friendliness 45/100

velt-lang/velt#563 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
A field initializer of -0 stores +0 (1 / f.a prints Infinity; Node prints -Infinity)
Open
- Is something wrong?
area:lowering kind:bug

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

velt-lang/velt#562 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
numbers: (a + b) | 0 with an operand at or above 2^53 is not rounded to a double first
Open
- Is something wrong?
area:lowering kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#561 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
velt_opt: drop the zero fill of new objects whose constructor writes every field
Open
- Is something wrong?
Difficulty 5/5 Over a week Newbie friendliness 22/100

velt-lang/velt#560 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
velt_opt: devirtualize calls on objects whose class is known from their allocation
Open
- Is something wrong?
Difficulty 4/5 3-5 days Newbie friendliness 55/100

velt-lang/velt#559 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
velt_opt: heap_sroa keeps objects on the heap when a write and a later read use two names for them
Open
- Is something wrong?
Difficulty 4/5 3-5 days Newbie friendliness 45/100

velt-lang/velt#558 · 1 comment · Opened Oct 5, 2026

Maintainers usually reply within 1 day
velt_rt: debug allocator test frees quarantined blocks through the wrong inner allocator under VELT_RT_DEBUG_ALLOC=1
Open
- Is something wrong?
area:runtime kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#555 · Opened Oct 5, 2026

Maintainers usually reply within 1 day
Flaky: veltc::reload reload_goldens is a timing check ("background GET /slow finished before the reload")
Open
- Is something wrong?
area:tooling kind:bug

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

velt-lang/velt#544 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Recursive drop overflows the stack on long linked chains (wasm at 5000 nodes; native?)
Open
- Is something wrong?
area:lowering area:runtime kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 45/100

velt-lang/velt#543 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
velt run: int32 helpers and numrep don't apply at OptLevel::None (3x slower than release on #521's loop)
Open
- Is something wrong?
Difficulty 4/5 3-5 days Newbie friendliness 38/100

velt-lang/velt#539 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Math.floor/trunc/ceil are libm calls on x86_64 (baseline target has no roundsd)
Open
- Is something wrong?
Difficulty 4/5 3-5 days Newbie friendliness 42/100

velt-lang/velt#535 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
% on number is a libm fmod call (10 ns): whole-number fast path, then integer narrowing
Open
- Is something wrong?
kind:perf

Difficulty 5/5 Over a week Newbie friendliness 34/100

velt-lang/velt#532 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Design: the number model — JS-exact `number`, proven integer representation, explicit widths for speed
Open
- Is something wrong?
area:lowering area:sema kind:design kind:perf

Difficulty 5/5 Over a week Newbie friendliness 25/100

velt-lang/velt#525 · 3 comments · Opened Oct 4, 2026

Maintainers usually reply within 1 day
LSP: quick fix to convert a plain // comment above an export to a doc comment
Open
- Is something wrong?
area:tooling kind:feature

Difficulty 4/5 3-5 days Newbie friendliness 57/100

velt-lang/velt#518 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Docs and completion for compiler-only built-ins (console.log, push, Promise.all, ...)
Open
- Is something wrong?
area:sema area:tooling kind:feature

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#516 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
std: prelude doc comments seeded from TypeScript's lib .d.ts JSDoc
Open
- Is something wrong?
area:std kind:feature

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#515 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
LSP: show doc comments in hover, completion and signature help
Open
- Is something wrong?
area:tooling kind:feature

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#514 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Documentation support: doc comments in the editor and velt doc
Open
- Is something wrong?
area:std area:tooling kind:design

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#512 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Numbers and clone: -0 from inferred-integer arithmetic, clone() of a cyclic graph recurses forever
Open
- Is something wrong?
area:lowering kind:bug

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#508 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Follow-ups from #454: super() in both if/else arms, duplicate spread diagnostic, fix-it spellings, Object.keys on interface values
Open
- Is something wrong?
area:sema kind:bug

Difficulty 5/5 Over a week Newbie friendliness 30/100

velt-lang/velt#506 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
sema: velt check on a 4000-function generic call chain takes ~10 s (an unidentified superlinear pass)
Open
- Is something wrong?
area:sema kind:perf

Difficulty 5/5 Over a week Newbie friendliness 38/100

velt-lang/velt#503 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Timers: keep the process alive while timers are pending, accept void callbacks, decide setInterval overlap
Open
- Is something wrong?
area:runtime area:std kind:feature

Difficulty 5/5 Over a week Newbie friendliness 30/100

velt-lang/velt#501 · 1 comment · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Mutex.with: a callback that writes an unrelated field of this (this.count += 1) is rejected
Open
- Is something wrong?
area:sema kind:bug

Difficulty 3/5 1-2 days Newbie friendliness 65/100

velt-lang/velt#493 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Mutex.with: 'still used after with stored it' is decided by source position, missing uses on the next loop iteration
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 58/100

velt-lang/velt#490 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Mutex.with: a generator callback panics at run time; a generic applyAll used as a value gets an unrelated error
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 57/100

velt-lang/velt#482 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Field initializers and default values cannot use expressions that need temporaries (spread crashes)
Open
- Is something wrong?
Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#480 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
xtask tests use a compile-time CARGO_MANIFEST_DIR, so a shared target dir + sccache runs them against another worktree
Open
- Is something wrong?
area:tooling kind:bug

Difficulty 3/5 1-2 days Newbie friendliness 55/100

velt-lang/velt#474 · Opened Oct 4, 2026

Maintainers usually reply within 1 day
Accessors: (x.p ??= v) as a value is rejected, and (c.p = 2) as a value re-reads the getter
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#471 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
let n = xs.length can't be added to a usize variable (const n can), and the error has no note
Open
- Is something wrong?
area:sema kind:bug

Difficulty 3/5 1-2 days Newbie friendliness 72/100

velt-lang/velt#468 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A closure assigning a captured variable races when an HTTP handler calls it
Open
- Is something wrong?
area:sema

Difficulty 5/5 Over a week Newbie friendliness 38/100

velt-lang/velt#467 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Promise copies: remaining paths that reach the run-time panic, and tests for the check
Open
- Is something wrong?
Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#464 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
JSON.stringify writes an absent optional field as null (JavaScript omits it)
Open
- Is something wrong?
area:std kind:bug

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#463 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A union of integer literals divides as integers, and Math.trunc rejects it
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 55/100

velt-lang/velt#462 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A suffixed integer literal (10u8) counts as an inferred integer
Open
- Is something wrong?
area:sema kind:bug

Difficulty 3/5 1-2 days Newbie friendliness 68/100

velt-lang/velt#451 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
String += on an element or call receiver evaluates the receiver twice
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#446 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A non-escaping closure or const me = this should not make a class reference-counted
Open
- Is something wrong?
area:lowering area:sema kind:perf

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#444 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
TypeScript compatibility: valid TypeScript that Velt rejects (collected during reviews)
Open
- Is something wrong?
area:sema area:std kind:bug

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#443 · 4 comments · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Closure-typed fields and arrays: infer from the initializer, and adapt () => usize to () => number
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 51/100

velt-lang/velt#441 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Mutex.with with an async callback: hold the lock until its promise settles
Open
- Is something wrong?
area:lowering area:std kind:feature

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#439 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
switch: accept what TypeScript accepts (non-exhaustive, non-literal cases on unions, duplicate cases)
Open
- Is something wrong?
area:sema kind:feature

Difficulty 3/5 1-2 days Newbie friendliness 65/100

velt-lang/velt#438 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A local declared from an integer literal and later given a fraction should be a JS number (x /= 2, t += 0.5)
Open
- Is something wrong?
area:sema kind:bug

Difficulty 4/5 3-5 days Newbie friendliness 48/100

velt-lang/velt#437 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A derived class constructor may omit super() (TypeScript requires it: TS2377)
Open
- Is something wrong?
area:sema kind:bug

Difficulty 3/5 1-2 days Newbie friendliness 58/100

velt-lang/velt#422 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Utility types: align Omit unknown keys, Required on T | null, and forward references with TypeScript
Open
- Is something wrong?
area:sema kind:feature

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#418 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day
HTTP handlers that capture a non-thread-safe resource should run like Node (TypeScript compatibility)
Open
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area:runtime area:sema area:std kind:design

Difficulty 5/5 Over a week Newbie friendliness 25/100

velt-lang/velt#417 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Republish the sqlite package's native bundles with the velt_<package>__ export prefix
Open
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area:tooling

Difficulty 4/5 3-5 days Newbie friendliness 46/100

velt-lang/velt#416 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
spawn(f()) starts f when a worker first polls the task, not at the call (timers start late; the newest task waits for its spawner)
Open
- Is something wrong?
area:runtime

Difficulty 1/5 1-3 hours Newbie friendliness 72/100

velt-lang/velt#415 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day
A disposable object copied into a spawned task is disposed twice
Open
- Is something wrong?
area:sema

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#410 · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Keeping a callback in an interface method, function value or closure is rejected (cannot keep a copy of a borrowed function parameter)
Open
- Is something wrong?
area:lowering area:sema kind:design

Difficulty 5/5 Over a week Newbie friendliness 25/100

velt-lang/velt#407 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day
Strings: heap slice copies, so rest = rest.slice(n) parsers are O(n²)
Open
- Is something wrong?
area:runtime

Difficulty 5/5 Over a week Newbie friendliness 35/100

velt-lang/velt#402 · 1 comment · Opened Oct 3, 2026

Maintainers usually reply within 1 day

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