[DevShoaib78]

Fixes #3251. Also covers the case in #2521.

Any two array schemas counted as the same type in getAutoConversionRank, so both snippets in the issue silently generated invalid WGSL. Arrays now get a cast when the lengths differ or the elements need one, the same way structs do.

What it generates now

const arr = [1.5, 2.5, 3.5];
const b = d.arrayOf(d.u32, 3)(arr);
// let b = array<u32, 3>(u32(arr[0]), u32(arr[1]), u32(arr[2]));

Arrays of different structs convert element by element too, as in #2521.

Decisions to check

• Different lengths throw, since the issue doesn't say what should happen and I can't see a sensible conversion: Cannot auto-convert array ... because their element counts differ.
• A source with possible side effects throws and asks to store it in a variable first, like the struct cast, because it would otherwise be evaluated once per element.
• Array literals stay ArrayExpressions, so their elements can still be known at comptime. The nested array test in comptime.test.ts needs this.
• Runtime-sized arrays (element count 0) are left as they were.
• Two separate schemas of the same array type still don't cast.
• The cast logs the existing implicit-conversion warning, even for an explicit d.arrayOf(...)(arr). Struct casts do the same.

Testing

Added 5 tests to array.test.ts. 4 of them fail without the fix; the fifth pins that identical schemas don't cast. tsc, oxlint and oxfmt are clean on the changed files.

On Windows, vitest run --project=!browser has the same 20 failures with and without this change, in tgpu-gen, unplugin-typegpu and the docs probability example, and nothing new. I did not run the built-package tests or the circular dependency check (dpdm found no entry files on Windows), and I only checked the generated WGSL text, not on a real GPU.

[pullfrog]

Caution

This PR introduces a circular dependency. dpdm reports one cycle on this branch and none on main, so the required test:circular-deps job (.github/workflows/test-misc.yml) will fail.

Reviewed changes

• Array element-wise casting — needsArrayCast now flags two WgslArray schemas as needing a cast when their element counts differ or their element types need conversion, so mismatched arrays are no longer silently treated as the same type.
• Cast codegen — the case 'cast' branch in applyActionToSnippet resolves an array→array cast to array<T,N>(elem0, elem1, …), converting each element; array literals stay ArrayExpressions to preserve comptime values.
• Tests — five cases added to array.test.ts (variable→array element conversion, struct-element conversion, same-type no-cast, length mismatch throws, side-effecting source throws). I confirmed four of them fail on the pre-fix conversion.ts and that the rest of packages/typegpu/tests (3085 tests) and the docs example snapshots still pass; tsc, oxlint, and oxfmt are clean on the two files.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using deepseek-v4.1-flash (free via Pullfrog for OSS) ｜ 𝕏}

[pullfrog]

This new import edge closes a dependency cycle and fails the repo's test:circular-deps gate. dpdm exits 0 on main but exits 1 on this branch, reporting:

core/function/createCallableSchema.ts
  -> tgsl/conversion.ts
  -> tgsl/generationHelpers.ts
  -> data/numeric.ts
  -> core/function/createCallableSchema.ts

Technical details

# Move `ArrayExpression` out of `generationHelpers.ts` to break the cycle

## Affected sites
- `packages/typegpu/src/tgsl/conversion.ts:30` — new `import { ArrayExpression } from './generationHelpers.ts'`.
- `packages/typegpu/src/tgsl/generationHelpers.ts:2` — imports `../data/numeric.ts`, which imports `../core/function/createCallableSchema.ts`, which imports `./conversion.ts` (closing the loop).

## Required outcome
- The import graph reachable from `packages/**/src/index.ts` must be acyclic (the repo enforces this with `pnpm test:circular-deps` in `.github/workflows/test-misc.yml` and in the `prepack` script).

## Suggested approach
- Move the `ArrayExpression` class (or just an `isArrayExpression` guard) into a leaf module that does not transitively reach `data/numeric.ts` / `createCallableSchema.ts` (its dependencies would be `data/snippet.ts`, `data/wgslTypes.ts`, `shared/symbols.ts`, `errors.ts`, `types.ts`), and import it from both `generationHelpers.ts` and `conversion.ts`.
- `conversion.ts`'s existing imports do not reach `createCallableSchema` (base `12f5cba` is cycle-free), so a genuinely leaf module breaks the loop.
- Verify with `pnpm test:circular-deps`.

[Copilot]

🟡 Changes recommended

Array conversion has critical gaps: nested-array inference depends on row order and can truncate fractional values, while aliases bypass required element casts and length checks.

2 open issues

• Array aliases bypass element conversion and length checks · New
• Nested array inference depends on row order · New

What changed in this PR

This PR updates TypeGPU’s array conversions to address invalid WGSL reported in #3251 and #2521.

Changes:

• Adds element-by-element casts between array schemas, including arrays of different structs.
• Rejects mismatched lengths and conversions that would repeat possible side effects, while preserving compile-time array literals.
• Adds five regression tests covering conversions, errors, and equivalent schemas.

File	Description
packages/​typegpu/​tests/​array.test.ts	Adds array-conversion regression tests.
packages/​typegpu/​src/​tgsl/​conversion.ts	Adds array-cast detection, element conversion, and validation.

_{Review effort: Balanced}