Review fixes

Author: iwoplaza

packages/typegpu/src/tgsl/accessIndex.ts

@@ -25,10 +25,16 @@ export function accessIndex(target: Snippet, indexArg: Snippet | number): Snippe
 
     if (target.origin === 'constant-immutable-def') {
       // Constant refs stay const unless the element/index forces runtime materialization
-      origin = index.origin === 'constant' ? 'constant-immutable-def' : 'runtime-immutable-def';
+      origin =
+        index.origin === 'constant' || index.origin === 'constant-immutable-def'
+          ? 'constant-immutable-def'
+          : 'runtime-immutable-def';
     } else if (target.origin === 'constant') {
       // Ephemeral constants indexed with constants stay constant, otherwise they become runtime-known
-      origin = index.origin === 'constant' ? 'constant' : 'runtime';
+      origin =
+        index.origin === 'constant' || index.origin === 'constant-immutable-def'
+          ? 'constant'
+          : 'runtime';
     } else {
       // Fallthrough
       origin = target.origin;

packages/typegpu/tests/constant.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it } from 'vitest';
 import { d, tgpu } from '../src/index.js';
+import { extractSnippetFromFn } from './utils/parseResolved.ts';
 
 const Boid = d.struct({
   pos: d.vec3f,
@@ -190,4 +191,16 @@ describe('tgpu.const', () => {
       - fn*:testFn(): 'c.$.x = 1' is invalid, because the left side is a constant.]
     `);
   });
+
+  it('allows for tgpu.const-tgpu.const index access', () => {
+    const myConstArray = tgpu.const(d.arrayOf(d.u32, 2), [1, 2]);
+    const myConstIndex = tgpu.const(d.u32, 1);
+
+    const fn = () => {
+      'use gpu';
+      return myConstArray.$[myConstIndex.$];
+    };
+
+    expect(extractSnippetFromFn(fn).origin).toBe('constant-immutable-def');
+  });
 });