Add shader validation tests about clip_distances and the extension (#…

…3946)

This patch adds shader validation tests to verify that using
`clip_distances` the extension `clip_distances` must be enabled in the
shader.

src/webgpu/shader/validation/extension/clip_distances.spec.ts

@@ -0,0 +1,43 @@
+export const description = `
+Validation tests for the clip_distances extension
+`;
+
+import { makeTestGroup } from '../../../../common/framework/test_group.js';
+import { ShaderValidationTest } from '../shader_validation_test.js';
+
+export const g = makeTestGroup(ShaderValidationTest);
+
+g.test('use_clip_distances_requires_extension_enabled')
+  .desc(
+    `Checks that the clip_distances built-in variable is only allowed with the WGSL extension
+     clip_distances enabled in shader and the WebGPU extension clip-distances supported on the
+     device.`
+  )
+  .params(u =>
+    u.combine('requireExtension', [true, false]).combine('enableExtension', [true, false])
+  )
+  .beforeAllSubcases(t => {
+    if (t.params.requireExtension) {
+      t.selectDeviceOrSkipTestCase({ requiredFeatures: ['clip-distances'] });
+    }
+  })
+  .fn(t => {
+    const { requireExtension, enableExtension } = t.params;
+
+    t.expectCompileResult(
+      requireExtension && enableExtension,
+      `
+        ${enableExtension ? 'enable clip_distances;' : ''}
+        struct VertexOut {
+          @builtin(clip_distances) my_clip_distances : array<f32, 1>,
+          @builtin(position) my_position : vec4f,
+        }
+        @vertex fn main() -> VertexOut {
+          var output : VertexOut;
+          output.my_clip_distances[0] = 1.0;
+          output.my_position = vec4f(0.0, 0.0, 0.0, 1.0);
+          return output;
+        }
+    `
+    );
+  });