invalid sourcemap with at layer

test/at-rule.test.ts

@@ -48,4 +48,32 @@ test('clone spaces from another at-rule', () => {
   is(rule.toString(), '@page 1{}')
 })
 
+test('at layer', () => {
+  let root = parse(`@layer foo {\n  @layer one, two\n}`)
+  let layer1 = root.nodes[0] as AtRule;
+  let layer2 = layer1.nodes[0] as AtRule;
+
+  is(root.source?.start?.offset, 0)
+  is(root.source?.start?.line, 1)
+  is(root.source?.start?.column, 1)
+
+  is(layer1.source?.start?.offset, 0)
+  is(layer1.source?.start?.line, 1)
+  is(layer1.source?.start?.column, 1)
+
+  is(layer1.source?.end?.offset, 31)
+  is(layer1.source?.end?.line, 3)
+  is(layer1.source?.end?.column, 1)
+
+  is(layer2.source?.start?.offset, 15)
+  is(layer2.source?.start?.line, 2)
+  is(layer2.source?.start?.column, 3)
+
+  is(layer2.source?.end?.offset, 29)
+  is(layer2.source?.end?.line, 2)
+  is(layer2.source?.end?.column, 17)
+
+  is(root.toString(), '@layer foo {\n  @layer one, two\n}')
+})
+
 test.run()

test/map.test.ts

@@ -104,6 +104,21 @@ test('generate right source map', () => {
   })
 })
 
+test('generate right source map for at layer', () => {
+  let css = '@layer extensions {\n  @layer one, two\n}'
+  let processor = postcss(() => {
+    /* noop */
+  })
+
+  let result = processor.process(css, {
+    from: 'a.css',
+    to: 'b.css',
+    map: true
+  })
+
+  read(result)
+})
+
 test('changes previous source map', () => {
   let css = 'a { color: black }'