From e9af65ef78ff3116a9cdf927bbbe0fb5eecd42c3 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 11:14:55 +0200
Subject: [PATCH 01/11] Add tests

---
 packages/typegpu/tests/slot.test.ts | 66 ++++++++++++++++++++++++++++-
 1 file changed, 64 insertions(+), 2 deletions(-)

diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index a9a70bee84..261733f846 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -1,7 +1,7 @@
-import { describe, expect } from 'vitest';
+import { describe, expect, vi } from 'vitest';
 import * as d from '../src/data/index.ts';
-import * as std from '../src/std/index.ts';
 import tgpu from '../src/index.ts';
+import * as std from '../src/std/index.ts';
 import { it } from './utils/extendedIt.ts';
 import { asWgsl } from './utils/parseResolved.ts';
 
@@ -363,4 +363,66 @@ describe('tgpu.slot', () => {
       }"
     `);
   });
+
+  it('warns when the slot is unused in WGSL-implemented functions', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const colorSlot = tgpu.slot<d.v3f>();
+
+    const getColor = tgpu.fn([], d.vec3f)`() { return vec3f(); }`;
+
+    getColor.with(colorSlot, d.vec3f(0, 1, 0));
+
+    expect(warnSpy).toHaveBeenCalledWith();
+  });
+
+  it('warns when the slot is unused in TGSL-implemented functions', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const colorSlot = tgpu.slot<d.v3f>();
+
+    const getColor = tgpu.fn([], d.vec3f)(() => {
+      return d.vec3f();
+    });
+
+    getColor.with(colorSlot, d.vec3f(0, 1, 0));
+
+    expect(warnSpy).toHaveBeenCalledWith();
+  });
+
+  it('warns when the slot is unused in WGSL-implemented pipeline', ({ root }) => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const colorSlot = tgpu.slot<d.v3f>();
+
+    const computeFn = tgpu['~unstable'].computeFn({
+      workgroupSize: [1, 1, 1],
+      in: { gid: d.builtin.globalInvocationId },
+    })`{ }`;
+
+    root['~unstable']
+      .with(colorSlot, d.vec3f(1, 0, 1))
+      .withCompute(computeFn)
+      .createPipeline();
+
+    expect(warnSpy).toHaveBeenCalledWith();
+  });
+
+  it('warns when the slot is unused in TGSL-implemented pipeline', ({ root }) => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const colorSlot = tgpu.slot<d.v3f>();
+
+    const computeFn = tgpu['~unstable'].computeFn({
+      workgroupSize: [1, 1, 1],
+      in: { gid: d.builtin.globalInvocationId },
+    })(() => {});
+
+    root['~unstable']
+      .with(colorSlot, d.vec3f(1, 0, 1))
+      .withCompute(computeFn)
+      .createPipeline();
+
+    expect(warnSpy).toHaveBeenCalledWith();
+  });
 });

From 14e34af91bd749f760b6f2bd7f1b80b66c898d46 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 12:49:58 +0200
Subject: [PATCH 02/11] Add a semi-working implementation

---
 packages/typegpu/src/resolutionCtx.ts | 11 +++++-
 packages/typegpu/tests/slot.test.ts   | 56 +++++++++++++++++++++++----
 2 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index a25252031f..f274410c7e 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -69,7 +69,7 @@ import type {
 } from './types.ts';
 import { CodegenState, isSelfResolvable, NormalState } from './types.ts';
 import type { WgslExtension } from './wgslExtensions.ts';
-import { hasTinyestMetadata } from './shared/meta.ts';
+import { getName, hasTinyestMetadata } from './shared/meta.ts';
 
 /**
  * Inserted into bind group entry definitions that belong
@@ -521,9 +521,11 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     };
   }
 
+  private usedSlots: WeakSet<TgpuSlot<unknown>> = new WeakSet();
   readSlot<T>(slot: TgpuSlot<T>): T {
     const value = this._itemStateStack.readSlot(slot);
 
+    this.usedSlots.add(slot);
     if (value === undefined) {
       throw new MissingSlotValueError(slot);
     }
@@ -538,6 +540,13 @@ export class ResolutionCtxImpl implements ResolutionCtx {
       return callback();
     } finally {
       this._itemStateStack.popSlotBindings();
+      pairs.forEach((pair) => {
+        !this.usedSlots.has(pair[0]) && console.warn(
+          `Slot '${getName(pair[0])}' with value '${
+            pair[1]
+          }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .`,
+        );
+      });
     }
   }
 
diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index 261733f846..e6f2076038 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -371,9 +371,13 @@ describe('tgpu.slot', () => {
 
     const getColor = tgpu.fn([], d.vec3f)`() { return vec3f(); }`;
 
-    getColor.with(colorSlot, d.vec3f(0, 1, 0));
+    const main = getColor.with(colorSlot, d.vec3f(0, 1, 0));
 
-    expect(warnSpy).toHaveBeenCalledWith();
+    tgpu.resolve({ externals: { main } });
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+    );
   });
 
   it('warns when the slot is unused in TGSL-implemented functions', () => {
@@ -385,9 +389,13 @@ describe('tgpu.slot', () => {
       return d.vec3f();
     });
 
-    getColor.with(colorSlot, d.vec3f(0, 1, 0));
+    const main = getColor.with(colorSlot, d.vec3f(0, 1, 0));
 
-    expect(warnSpy).toHaveBeenCalledWith();
+    tgpu.resolve({ externals: { main } });
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+    );
   });
 
   it('warns when the slot is unused in WGSL-implemented pipeline', ({ root }) => {
@@ -400,12 +408,16 @@ describe('tgpu.slot', () => {
       in: { gid: d.builtin.globalInvocationId },
     })`{ }`;
 
-    root['~unstable']
+    const pipeline = root['~unstable']
       .with(colorSlot, d.vec3f(1, 0, 1))
       .withCompute(computeFn)
       .createPipeline();
 
-    expect(warnSpy).toHaveBeenCalledWith();
+    tgpu.resolve({ externals: { pipeline } });
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+    );
   });
 
   it('warns when the slot is unused in TGSL-implemented pipeline', ({ root }) => {
@@ -418,11 +430,41 @@ describe('tgpu.slot', () => {
       in: { gid: d.builtin.globalInvocationId },
     })(() => {});
 
-    root['~unstable']
+    const pipeline = root['~unstable']
       .with(colorSlot, d.vec3f(1, 0, 1))
       .withCompute(computeFn)
       .createPipeline();
 
+    tgpu.resolve({ externals: { pipeline } });
+
+    expect(warnSpy).toHaveBeenCalledWith(
+      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+    );
+  });
+
+  it('distinguishes different slot usages', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const colorSlot = tgpu.slot<d.v3f>();
+
+    const getColorUsingSlot = tgpu
+      .fn([], d.vec3f)(() => {
+        return colorSlot.$;
+      })
+      .with(colorSlot, d.vec3f(0, 1, 0));
+
+    const getColor = tgpu
+      .fn([], d.vec3f)(() => {
+        return d.vec3f();
+      })
+      .with(colorSlot, d.vec3f(2, 1, 0));
+
+    const main = tgpu.fn([])(() => {
+      getColorUsingSlot();
+      getColor();
+    });
+    tgpu.resolve({ externals: { main } });
+
     expect(warnSpy).toHaveBeenCalledWith();
   });
 });

From 7d8b4690231f2fd094bcb96f10f3c119319c9b13 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 13:40:56 +0200
Subject: [PATCH 03/11] Push the slot usage down to the stack

---
 packages/typegpu/src/resolutionCtx.ts | 17 ++++++++++-------
 packages/typegpu/tests/slot.test.ts   |  4 +++-
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index f274410c7e..b37bcdf5d1 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -93,6 +93,7 @@ export type ResolutionCtxImplOptions = {
 type SlotBindingLayer = {
   type: 'slotBinding';
   bindingMap: WeakMap<TgpuSlot<unknown>, unknown>;
+  usedSet: WeakSet<TgpuSlot<unknown>>;
 };
 
 type BlockScopeLayer = {
@@ -141,11 +142,13 @@ class ItemStateStackImpl implements ItemStateStack {
     this._stack.push({
       type: 'slotBinding',
       bindingMap: new WeakMap(pairs),
+      usedSet: new WeakSet(),
     });
   }
 
-  popSlotBindings() {
-    this.pop('slotBinding');
+  popSlotBindings(): WeakSet<TgpuSlot<unknown>> {
+    const slotBindings = this.pop('slotBinding') as SlotBindingLayer;
+    return slotBindings.usedSet;
   }
 
   pushFunctionScope(
@@ -188,10 +191,11 @@ class ItemStateStackImpl implements ItemStateStack {
       throw new Error(`Internal error, expected a ${type} layer to be on top.`);
     }
 
-    this._stack.pop();
+    const poppedValue = this._stack.pop();
     if (type === 'item') {
       this._itemDepth--;
     }
+    return poppedValue;
   }
 
   readSlot<T>(slot: TgpuSlot<T>): T | undefined {
@@ -202,6 +206,7 @@ class ItemStateStackImpl implements ItemStateStack {
         layer.usedSlots.add(slot);
       } else if (layer?.type === 'slotBinding') {
         const boundValue = layer.bindingMap.get(slot);
+        layer.usedSet.add(slot);
 
         if (boundValue !== undefined) {
           return boundValue as T;
@@ -521,11 +526,9 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     };
   }
 
-  private usedSlots: WeakSet<TgpuSlot<unknown>> = new WeakSet();
   readSlot<T>(slot: TgpuSlot<T>): T {
     const value = this._itemStateStack.readSlot(slot);
 
-    this.usedSlots.add(slot);
     if (value === undefined) {
       throw new MissingSlotValueError(slot);
     }
@@ -539,9 +542,9 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     try {
       return callback();
     } finally {
-      this._itemStateStack.popSlotBindings();
+      const usedSlots = this._itemStateStack.popSlotBindings();
       pairs.forEach((pair) => {
-        !this.usedSlots.has(pair[0]) && console.warn(
+        !usedSlots.has(pair[0]) && console.warn(
           `Slot '${getName(pair[0])}' with value '${
             pair[1]
           }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .`,
diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index e6f2076038..5658c85160 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -465,6 +465,8 @@ describe('tgpu.slot', () => {
     });
     tgpu.resolve({ externals: { main } });
 
-    expect(warnSpy).toHaveBeenCalledWith();
+    expect(warnSpy).toHaveBeenCalledWith(
+      "Slot 'colorSlot' with value 'vec3f(2, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+    );
   });
 });

From dc99c35c8cbb7d75e3c7fd597d251f1d7b1a6a90 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 13:46:56 +0200
Subject: [PATCH 04/11] Remove unused slot from double-buffering

---
 .../src/examples/simulation/fluid-double-buffering/index.ts      | 1 -
 1 file changed, 1 deletion(-)

diff --git a/apps/typegpu-docs/src/examples/simulation/fluid-double-buffering/index.ts b/apps/typegpu-docs/src/examples/simulation/fluid-double-buffering/index.ts
index e26cb79e6e..35adce8ad3 100644
--- a/apps/typegpu-docs/src/examples/simulation/fluid-double-buffering/index.ts
+++ b/apps/typegpu-docs/src/examples/simulation/fluid-double-buffering/index.ts
@@ -454,7 +454,6 @@ function makePipelines(
   outputGridMutable: TgpuBufferMutable<GridData>,
 ) {
   const initWorldAction = root['~unstable']
-    .with(inputGridSlot, outputGridMutable)
     .with(outputGridSlot, outputGridMutable)
     .prepareDispatch((xu, yu) => {
       'use gpu';

From 2cb06ebca4245c7b07b16ba5b676d4bfa648269d Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 13:51:24 +0200
Subject: [PATCH 05/11] Fix the message

---
 packages/typegpu/src/resolutionCtx.ts |  2 +-
 packages/typegpu/tests/slot.test.ts   | 10 +++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index b37bcdf5d1..5b3d348cff 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -547,7 +547,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
         !usedSlots.has(pair[0]) && console.warn(
           `Slot '${getName(pair[0])}' with value '${
             pair[1]
-          }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .`,
+          }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.`,
         );
       });
     }
diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index 5658c85160..81bdbf2aa4 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -376,7 +376,7 @@ describe('tgpu.slot', () => {
     tgpu.resolve({ externals: { main } });
 
     expect(warnSpy).toHaveBeenCalledWith(
-      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
 
@@ -394,7 +394,7 @@ describe('tgpu.slot', () => {
     tgpu.resolve({ externals: { main } });
 
     expect(warnSpy).toHaveBeenCalledWith(
-      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+      "Slot 'colorSlot' with value 'vec3f(0, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
 
@@ -416,7 +416,7 @@ describe('tgpu.slot', () => {
     tgpu.resolve({ externals: { pipeline } });
 
     expect(warnSpy).toHaveBeenCalledWith(
-      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
 
@@ -438,7 +438,7 @@ describe('tgpu.slot', () => {
     tgpu.resolve({ externals: { pipeline } });
 
     expect(warnSpy).toHaveBeenCalledWith(
-      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+      "Slot 'colorSlot' with value 'vec3f(1, 0, 1)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
 
@@ -466,7 +466,7 @@ describe('tgpu.slot', () => {
     tgpu.resolve({ externals: { main } });
 
     expect(warnSpy).toHaveBeenCalledWith(
-      "Slot 'colorSlot' with value 'vec3f(2, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared in the '$uses' array of the relevant .",
+      "Slot 'colorSlot' with value 'vec3f(2, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
 });

From a298ddbe8c7ecaf42bc4a03c3671fd539ab2a2cf Mon Sep 17 00:00:00 2001
From: Aleksander Katan <56294622+aleksanderkatan@users.noreply.github.com>
Date: Thu, 23 Oct 2025 13:53:38 +0200
Subject: [PATCH 06/11] Update packages/typegpu/src/resolutionCtx.ts

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
---
 packages/typegpu/src/resolutionCtx.ts | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index 5b3d348cff..9fc4aa84d0 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -544,11 +544,13 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     } finally {
       const usedSlots = this._itemStateStack.popSlotBindings();
       pairs.forEach((pair) => {
-        !usedSlots.has(pair[0]) && console.warn(
-          `Slot '${getName(pair[0])}' with value '${
-            pair[1]
-          }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.`,
-        );
+        if (!usedSlots.has(pair[0])) {
+          console.warn(
+            `Slot '${getName(pair[0])}' with value '${
+              pair[1]
+            }' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.`,
+          );
+        }
       });
     }
   }

From 512637a8535c71ff8bee96717124859bffd54142 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Thu, 23 Oct 2025 16:34:12 +0200
Subject: [PATCH 07/11] Fix repeated logs (and repeated slot refills)

---
 packages/typegpu/src/core/function/tgpuFn.ts |  1 -
 packages/typegpu/src/resolutionCtx.ts        |  2 +-
 packages/typegpu/tests/slot.test.ts          | 45 ++++++++++++++++++++
 3 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/packages/typegpu/src/core/function/tgpuFn.ts b/packages/typegpu/src/core/function/tgpuFn.ts
index 4c5a3cc937..c1bc85d0a6 100644
--- a/packages/typegpu/src/core/function/tgpuFn.ts
+++ b/packages/typegpu/src/core/function/tgpuFn.ts
@@ -290,7 +290,6 @@ function createBoundFunction<ImplSchema extends AnyFn>(
       value: unknown,
     ): TgpuFn<ImplSchema> {
       return createBoundFunction(fn, [
-        ...pairs,
         [isAccessor(slot) ? slot.slot : slot, value],
       ]);
     },
diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index 9fc4aa84d0..3365882fec 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -206,9 +206,9 @@ class ItemStateStackImpl implements ItemStateStack {
         layer.usedSlots.add(slot);
       } else if (layer?.type === 'slotBinding') {
         const boundValue = layer.bindingMap.get(slot);
-        layer.usedSet.add(slot);
 
         if (boundValue !== undefined) {
+          layer.usedSet.add(slot);
           return boundValue as T;
         }
       } else if (
diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index 81bdbf2aa4..8174ca342d 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -469,4 +469,49 @@ describe('tgpu.slot', () => {
       "Slot 'colorSlot' with value 'vec3f(2, 1, 0)' was provided in a 'with' method despite not being utilized during resolution. Please verify that this slot was intended for use and that, in case of WGSL-implemented functions, it is properly declared with the '$uses' method.",
     );
   });
+
+  it('does not warn in nested case', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const sizeSlot = tgpu.slot<number>();
+
+    const getSize = tgpu.fn([], d.f32)(() => sizeSlot.$);
+
+    const main = tgpu.fn([], d.f32)(() => getSize()).with(sizeSlot, 1);
+
+    tgpu.resolve({ externals: { main } });
+
+    expect(warnSpy).toHaveBeenCalledTimes(0);
+  });
+
+  it('warns exactly as many times as there are unused slots', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const sizeSlot = tgpu.slot<number>();
+    const colorSlot = tgpu.slot<typeof RED | typeof GREEN>();
+    const shapeSlot = tgpu.slot<0 | 1 | 2>();
+
+    const getSize = tgpu.fn([], d.f32)`() { return sizeSlot; }`
+      .$uses({ sizeSlot })
+      .with(sizeSlot, 1)
+      .with(colorSlot, RED)
+      .with(shapeSlot, 2);
+
+    tgpu.resolve({ externals: { getSize } });
+
+    expect(warnSpy).toHaveBeenCalledTimes(2);
+  });
+
+  it('does not warn when default value is used', () => {
+    using warnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {});
+
+    const sizeSlot = tgpu.slot<number>(7);
+
+    const getSize = tgpu.fn([], d.f32)`() { return sizeSlot; }`
+      .$uses({ sizeSlot });
+
+    tgpu.resolve({ externals: { getSize } });
+
+    expect(warnSpy).toHaveBeenCalledTimes(0);
+  });
 });

From 52ccf524f876edfcf2384f4617dcae2b3aeb17c2 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Fri, 24 Oct 2025 16:24:23 +0200
Subject: [PATCH 08/11] Move types to, well, types.ts

---
 packages/typegpu/src/resolutionCtx.ts | 20 +++-----------------
 packages/typegpu/src/types.ts         | 17 +++++++++++++++++
 2 files changed, 20 insertions(+), 17 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index 3365882fec..f509654a70 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -65,6 +65,8 @@ import type {
   ItemLayer,
   ItemStateStack,
   ResolutionCtx,
+  SlotBindingLayer,
+  StackLayer,
   Wgsl,
 } from './types.ts';
 import { CodegenState, isSelfResolvable, NormalState } from './types.ts';
@@ -90,24 +92,8 @@ export type ResolutionCtxImplOptions = {
   readonly namespace: Namespace;
 };
 
-type SlotBindingLayer = {
-  type: 'slotBinding';
-  bindingMap: WeakMap<TgpuSlot<unknown>, unknown>;
-  usedSet: WeakSet<TgpuSlot<unknown>>;
-};
-
-type BlockScopeLayer = {
-  type: 'blockScope';
-  declarations: Map<string, Snippet>;
-};
-
 class ItemStateStackImpl implements ItemStateStack {
-  private _stack: (
-    | ItemLayer
-    | SlotBindingLayer
-    | FunctionScopeLayer
-    | BlockScopeLayer
-  )[] = [];
+  private _stack: StackLayer[] = [];
   private _itemDepth = 0;
 
   get itemDepth(): number {
diff --git a/packages/typegpu/src/types.ts b/packages/typegpu/src/types.ts
index 377e1905cb..d32418b134 100644
--- a/packages/typegpu/src/types.ts
+++ b/packages/typegpu/src/types.ts
@@ -107,6 +107,23 @@ export type FunctionScopeLayer = {
   reportedReturnTypes: Set<AnyData>;
 };
 
+export type SlotBindingLayer = {
+  type: 'slotBinding';
+  bindingMap: WeakMap<TgpuSlot<unknown>, unknown>;
+  usedSet: WeakSet<TgpuSlot<unknown>>;
+};
+
+export type BlockScopeLayer = {
+  type: 'blockScope';
+  declarations: Map<string, Snippet>;
+};
+
+export type StackLayer =
+  | ItemLayer
+  | SlotBindingLayer
+  | FunctionScopeLayer
+  | BlockScopeLayer;
+
 export interface ItemStateStack {
   readonly itemDepth: number;
   readonly topItem: ItemLayer;

From e6ddefd8d5318fe187e68387c8b3c871a3da9ea1 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Fri, 24 Oct 2025 16:52:12 +0200
Subject: [PATCH 09/11] Merge pop methods into one

---
 packages/typegpu/src/resolutionCtx.ts         | 32 +++++--------------
 packages/typegpu/src/types.ts                 |  9 +++---
 .../typegpu/tests/tgsl/wgslGenerator.test.ts  |  4 +--
 3 files changed, 14 insertions(+), 31 deletions(-)

diff --git a/packages/typegpu/src/resolutionCtx.ts b/packages/typegpu/src/resolutionCtx.ts
index f509654a70..85f2345c10 100644
--- a/packages/typegpu/src/resolutionCtx.ts
+++ b/packages/typegpu/src/resolutionCtx.ts
@@ -65,7 +65,6 @@ import type {
   ItemLayer,
   ItemStateStack,
   ResolutionCtx,
-  SlotBindingLayer,
   StackLayer,
   Wgsl,
 } from './types.ts';
@@ -120,10 +119,6 @@ class ItemStateStackImpl implements ItemStateStack {
     });
   }
 
-  popItem() {
-    this.pop('item');
-  }
-
   pushSlotBindings(pairs: SlotValuePair<unknown>[]) {
     this._stack.push({
       type: 'slotBinding',
@@ -132,11 +127,6 @@ class ItemStateStackImpl implements ItemStateStack {
     });
   }
 
-  popSlotBindings(): WeakSet<TgpuSlot<unknown>> {
-    const slotBindings = this.pop('slotBinding') as SlotBindingLayer;
-    return slotBindings.usedSet;
-  }
-
   pushFunctionScope(
     args: Snippet[],
     argAliases: Record<string, Snippet>,
@@ -156,10 +146,6 @@ class ItemStateStackImpl implements ItemStateStack {
     return scope;
   }
 
-  popFunctionScope() {
-    this.pop('functionScope');
-  }
-
   pushBlockScope() {
     this._stack.push({
       type: 'blockScope',
@@ -167,11 +153,9 @@ class ItemStateStackImpl implements ItemStateStack {
     });
   }
 
-  popBlockScope() {
-    this.pop('blockScope');
-  }
-
-  pop(type?: (typeof this._stack)[number]['type']) {
+  pop<T extends StackLayer['type']>(type: T): Extract<StackLayer, { type: T }>;
+  pop(): StackLayer | undefined;
+  pop(type?: StackLayer['type']) {
     const layer = this._stack[this._stack.length - 1];
     if (!layer || (type && layer.type !== type)) {
       throw new Error(`Internal error, expected a ${type} layer to be on top.`);
@@ -424,7 +408,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
   }
 
   popBlockScope() {
-    this._itemStateStack.popBlockScope();
+    this._itemStateStack.pop('blockScope');
   }
 
   generateLog(args: Snippet[]): Snippet {
@@ -478,7 +462,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
         returnType,
       };
     } finally {
-      this._itemStateStack.popFunctionScope();
+      this._itemStateStack.pop('functionScope');
     }
   }
 
@@ -528,7 +512,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
     try {
       return callback();
     } finally {
-      const usedSlots = this._itemStateStack.popSlotBindings();
+      const usedSlots = this._itemStateStack.pop('slotBinding').usedSet;
       pairs.forEach((pair) => {
         if (!usedSlots.has(pair[0])) {
           console.warn(
@@ -624,7 +608,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
 
       throw new ResolutionError(err, [derived]);
     } finally {
-      this._itemStateStack.popItem();
+      this._itemStateStack.pop('item');
     }
   }
 
@@ -695,7 +679,7 @@ export class ResolutionCtxImpl implements ResolutionCtx {
 
       throw new ResolutionError(err, [item]);
     } finally {
-      this._itemStateStack.popItem();
+      this._itemStateStack.pop('item');
     }
   }
 
diff --git a/packages/typegpu/src/types.ts b/packages/typegpu/src/types.ts
index d32418b134..64de7e6e46 100644
--- a/packages/typegpu/src/types.ts
+++ b/packages/typegpu/src/types.ts
@@ -130,9 +130,7 @@ export interface ItemStateStack {
   readonly topFunctionScope: FunctionScopeLayer | undefined;
 
   pushItem(): void;
-  popItem(): void;
   pushSlotBindings(pairs: SlotValuePair<unknown>[]): void;
-  popSlotBindings(): void;
   pushFunctionScope(
     args: Snippet[],
     argAliases: Record<string, Snippet>,
@@ -143,10 +141,11 @@ export interface ItemStateStack {
     returnType: AnyData | undefined,
     externalMap: Record<string, unknown>,
   ): FunctionScopeLayer;
-  popFunctionScope(): void;
   pushBlockScope(): void;
-  popBlockScope(): void;
-  pop(type?: 'functionScope' | 'blockScope' | 'slotBinding' | 'item'): void;
+
+  pop<T extends StackLayer['type']>(type: T): Extract<StackLayer, { type: T }>;
+  pop(): StackLayer | undefined;
+
   readSlot<T>(slot: TgpuSlot<T>): T | undefined;
   getSnippetById(id: string): Snippet | undefined;
   defineBlockVariable(id: string, snippet: Snippet): void;
diff --git a/packages/typegpu/tests/tgsl/wgslGenerator.test.ts b/packages/typegpu/tests/tgsl/wgslGenerator.test.ts
index 627ea920f7..6c9baf7064 100644
--- a/packages/typegpu/tests/tgsl/wgslGenerator.test.ts
+++ b/packages/typegpu/tests/tgsl/wgslGenerator.test.ts
@@ -320,7 +320,7 @@ describe('wgslGenerator', () => {
       const res2 = wgslGenerator.expression(
         (astInfo.ast?.body[1][1] as tinyest.Const)[2],
       );
-      ctx[$internal].itemStateStack.popBlockScope();
+      ctx[$internal].itemStateStack.pop('blockScope');
 
       expect(res2.dataType).toStrictEqual(d.vec4f);
 
@@ -335,7 +335,7 @@ describe('wgslGenerator', () => {
       const res4 = wgslGenerator.expression(
         astInfo.ast?.body[1][2] as tinyest.Expression,
       );
-      ctx[$internal].itemStateStack.popBlockScope();
+      ctx[$internal].itemStateStack.pop('blockScope');
 
       expect(res3.dataType).toStrictEqual(d.atomic(d.u32));
       expect(res4.dataType).toStrictEqual(Void);

From 614c03cf315c0a280b3aa4e86532e272cab07511 Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Tue, 28 Oct 2025 16:31:13 +0100
Subject: [PATCH 10/11] Change functions to keep all of their slots and
 `innerFn` instead of one slot and `fn`

---
 packages/typegpu/src/core/function/tgpuFn.ts |  3 ++-
 packages/typegpu/tests/slot.test.ts          | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/packages/typegpu/src/core/function/tgpuFn.ts b/packages/typegpu/src/core/function/tgpuFn.ts
index c1bc85d0a6..8983881c42 100644
--- a/packages/typegpu/src/core/function/tgpuFn.ts
+++ b/packages/typegpu/src/core/function/tgpuFn.ts
@@ -289,7 +289,8 @@ function createBoundFunction<ImplSchema extends AnyFn>(
       slot: TgpuSlot<unknown> | TgpuAccessor,
       value: unknown,
     ): TgpuFn<ImplSchema> {
-      return createBoundFunction(fn, [
+      return createBoundFunction(innerFn, [
+        ...pairs,
         [isAccessor(slot) ? slot.slot : slot, value],
       ]);
     },
diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index 8174ca342d..55f0c74eb0 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -514,4 +514,21 @@ describe('tgpu.slot', () => {
 
     expect(warnSpy).toHaveBeenCalledTimes(0);
   });
+
+  it('includes slot bindings in toString', () => {
+    const firstSlot = tgpu.slot<number>();
+    const secondSlot = tgpu.slot<number>();
+    const thirdSlot = tgpu.slot<number>();
+
+    const getSize = tgpu.fn([], d.f32)(() =>
+      firstSlot.$ + secondSlot.$ + thirdSlot.$
+    )
+      .with(firstSlot, 1)
+      .with(secondSlot, 2)
+      .with(thirdSlot, 3);
+
+    expect(getSize.toString()).toMatchInlineSnapshot(
+      `"fn:getSize[firstSlot=1, secondSlot=2, thirdSlot=3]"`,
+    );
+  });
 });

From d86ee0432f1719672c973c9ef556114a78bf8cee Mon Sep 17 00:00:00 2001
From: Aleksander Katan <aleksander.katan@swmansion.com>
Date: Tue, 28 Oct 2025 16:32:47 +0100
Subject: [PATCH 11/11] Add a test for nice object stringify

---
 packages/typegpu/tests/slot.test.ts | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/packages/typegpu/tests/slot.test.ts b/packages/typegpu/tests/slot.test.ts
index 55f0c74eb0..1e5237e873 100644
--- a/packages/typegpu/tests/slot.test.ts
+++ b/packages/typegpu/tests/slot.test.ts
@@ -531,4 +531,15 @@ describe('tgpu.slot', () => {
       `"fn:getSize[firstSlot=1, secondSlot=2, thirdSlot=3]"`,
     );
   });
+
+  it('safe stringifies in toString', () => {
+    const slot = tgpu.slot<d.v4f>();
+
+    const getSize = tgpu.fn([], d.f32)(() => slot.$.x)
+      .with(slot, d.vec4f(1, 2, 3, 4));
+
+    expect(getSize.toString()).toMatchInlineSnapshot(
+      `"fn:getSize[slot=vec4f(1, 2, 3, 4)]"`,
+    );
+  });
 });