Reproduce NPE in vertical class merger in presence of missing classes

Bug: 191124967
Change-Id: I62d2c3e0089675cec0e03f5182e25b5d9dfd211d
diff --git a/src/test/java/com/android/tools/r8/classmerging/vertical/VerticalClassMergingWithMissingSuperClassTest.java b/src/test/java/com/android/tools/r8/classmerging/vertical/VerticalClassMergingWithMissingSuperClassTest.java
new file mode 100644
index 0000000..d7091fb
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/classmerging/vertical/VerticalClassMergingWithMissingSuperClassTest.java
@@ -0,0 +1,77 @@
+// Copyright (c) 2021, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.classmerging.vertical;
+
+import static org.junit.Assert.assertEquals;
+
+import com.android.tools.r8.NoVerticalClassMerging;
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import com.android.tools.r8.utils.codeinspector.AssertUtils;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
+
+@RunWith(Parameterized.class)
+public class VerticalClassMergingWithMissingSuperClassTest extends TestBase {
+
+  @Parameter public TestParameters parameters;
+
+  @Parameters(name = "{0}")
+  public static TestParametersCollection data() {
+    return getTestParameters().withAllRuntimesAndApiLevels().build();
+  }
+
+  @Test
+  public void test() throws Exception {
+    AssertUtils.assertFailsCompilation(
+        () ->
+            testForR8(parameters.getBackend())
+                .addProgramClasses(Main.class, A.class, B.class, C.class)
+                .addKeepMainRule(Main.class)
+                .addDontWarn(MissingClass.class)
+                .addVerticallyMergedClassesInspector(
+                    inspector -> inspector.assertMergedIntoSubtype(B.class))
+                .enableNoVerticalClassMergingAnnotations()
+                .setMinApi(parameters.getApiLevel())
+                .compile()
+                .addRunClasspathFiles(buildOnDexRuntime(parameters, MissingClass.class))
+                .run(parameters.getRuntime(), Main.class)
+                .assertSuccessWithOutputLines("C", "A", "B"),
+        exception -> assertEquals(NullPointerException.class, exception.getCause().getClass()));
+  }
+
+  static class Main {
+    public static void main(String[] args) {
+      new C().m();
+    }
+  }
+
+  static class MissingClass {}
+
+  @NoVerticalClassMerging
+  static class A extends MissingClass {
+    void m() {
+      System.out.println("A");
+    }
+  }
+
+  static class B extends A {
+    @Override
+    void m() {
+      super.m();
+      System.out.println("B");
+    }
+  }
+
+  static class C extends B {
+    C() {
+      System.out.println("C");
+    }
+  }
+}