Ignore @tailwind utilities inside @reference

It’s triggering content scans and it doesn’t need to as no utilities in here will be printed anyway

Author: thecrypticace

packages/tailwindcss/src/index.test.ts

@@ -5478,7 +5478,7 @@ describe('feature detection', () => {
     expect(compiler.features & Features.Variants).toBeFalsy()
   })
 
-  test('`@tailwind utilities` is discovered inside `@reference`', async () => {
+  test('`@tailwind utilities` is ignored inside `@reference`', async () => {
     let compiler = await compile(
       css`
         @reference "tailwindcss/utilities";
@@ -5497,6 +5497,6 @@ describe('feature detection', () => {
 
     // We see @tailwind utilities but because of @reference it is ignored
     expect(compiler.features & Features.AtImport).toBeTruthy()
-    expect(compiler.features & Features.Utilities).toBeTruthy()
+    expect(compiler.features & Features.Utilities).toBeFalsy()
   })
 })

packages/tailwindcss/src/index.ts

@@ -162,6 +162,14 @@ async function parseCss(
         return
       }
 
+      // When inside `@reference` we should treat `@tailwind utilities` as if
+      // it wasn't there in the first place. This should also let `build()`
+      // return the cached static AST.
+      if (context.reference) {
+        replaceWith([])
+        return
+      }
+
       let params = segment(node.params, ' ')
       for (let param of params) {
         if (param.startsWith('source(')) {