impr: Warn when slot is unused

[aleksanderkatan]

So, now a warn is thrown when a slot is provided and not used!
Also, I "patched" the bug I talk about in the comment below. Here is an issue for a proper fix: #1854

The cases where I found a false-positive are:

• slots in a cyclic dependency (in addition to error being thrown, now a warn is displayed)
• overriden slots (the slots are kind of unused, but it may matter when providing a callback to a library):

    const colorSlot = tgpu.slot<string>(); // no default

    const getColor = tgpu.fn([], d.vec3f)`() -> vec3f {
      return colorSlot;
    }`
      .$uses({ colorSlot });

    const getColorWithGreen = getColor.with(colorSlot, GREEN);

    const main = tgpu.fn([])`() {
      getColorWithGreen();
    }`
      .$uses({ getColorWithGreen })
      .with(colorSlot, GREEN);

Let me know what you think.

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[Copilot]

Pull Request Overview

This PR adds a warning system to detect and alert developers when slots are provided to functions or pipelines but never actually used during resolution. The implementation tracks slot usage through the resolution context and emits console warnings for unused slots.

Key Changes:

• Enhanced slot tracking to differentiate between bound and used slots
• Added warning messages when slots are provided via .with() but remain unused
• Removed an unused slot binding from the fluid simulation example

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/typegpu/src/resolutionCtx.ts	Core implementation: added usedSet tracking and warning logic for unused slots
packages/typegpu/tests/slot.test.ts	Comprehensive test coverage for the warning feature across different scenarios
apps/typegpu-docs/src/examples/simulation/fluid-double-buffering/index.ts	Cleanup: removed unused inputGridSlot binding

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[aleksanderkatan]

I'm pretty sure I found a small bug in the resolution code. Take a look at these two snippets:

resolutionCtx.ts

  unwrap<T>(eventual: Eventual<T>): T {
    if (isProviding(eventual)) {
      return this.withSlots(
        eventual[$providing].pairs,
        () => this.unwrap(eventual[$providing].inner) as T,
      );
    }

tgpuFn.ts

    with(
      slot: TgpuSlot<unknown> | TgpuAccessor,
      value: unknown,
    ): TgpuFn<ImplSchema> {
      return createBoundFunction(fn, [
        ...pairs,
        [isAccessor(slot) ? slot.slot : slot, value],
      ]);
    },

I think that if we call .with multiple times, like:

    const getSize = tgpu.fn([], d.f32)`...`
      .$uses({ ... })
      .with(sizeSlot, 1)
      .with(colorSlot, RED)
      .with(shapeSlot, 2);

then withSlots is called with [sizeSlot, colorSlot, shapeSlot], then with [sizeSlot, colorSlot], then with [sizeSlot].

[reczkok]

Great work!