So siehts ganz gut aus !

node_modules/pug/test/extends-not-top-level/default.pug

@@ -0,0 +1,2 @@
+body
+  block content

node_modules/pug/test/extends-not-top-level/duplicate.pug

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+extends default
+extends default

node_modules/pug/test/extends-not-top-level/index.pug

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+mixin content
+  if bar
+    extends default
+    block content
+      block
+  else
+    block
+
++content
+  h1 Hello!

node_modules/pug/test/extends-not-top-level/index.test.js

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+const pug = require('../../');
+
+// regression test for #2404
+
+test('extends not top level should throw an error', () => {
+  expect(
+    () => pug.compileFile(
+      __dirname + '/index.pug'
+    )
+  ).toThrow('Declaration of template inheritance ("extends") should be the first thing in the file. There can only be one extends statement per file.');
+});
+
+test('duplicate extends should throw an error', () => {
+  expect(
+    () => pug.compileFile(
+      __dirname + '/duplicate.pug'
+    )
+  ).toThrow('Declaration of template inheritance ("extends") should be the first thing in the file. There can only be one extends statement per file.');
+});