Test for possible tree shaking improvement of reachable methods.

Bug: 150445487
Change-Id: I61a28ae6c46d27c52ee85d752e64a569e751480b
diff --git a/src/test/java/com/android/tools/r8/shaking/NonTargetedMethodTest.java b/src/test/java/com/android/tools/r8/shaking/NonTargetedMethodTest.java
new file mode 100644
index 0000000..715a846
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/shaking/NonTargetedMethodTest.java
@@ -0,0 +1,95 @@
+// Copyright (c) 2020, 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.shaking;
+
+import static com.android.tools.r8.utils.codeinspector.Matchers.isPresent;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import com.android.tools.r8.NeverClassInline;
+import com.android.tools.r8.NeverInline;
+import com.android.tools.r8.NeverMerge;
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import com.android.tools.r8.utils.StringUtils;
+import com.android.tools.r8.utils.codeinspector.ClassSubject;
+import com.android.tools.r8.utils.codeinspector.CodeInspector;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(Parameterized.class)
+public class NonTargetedMethodTest extends TestBase {
+
+  static final String EXPECTED = StringUtils.lines("A::foo", "C::bar");
+
+  private final TestParameters parameters;
+
+  @Parameterized.Parameters(name = "{0}")
+  public static TestParametersCollection data() {
+    return getTestParameters().withAllRuntimesAndApiLevels().build();
+  }
+
+  public NonTargetedMethodTest(TestParameters parameters) {
+    this.parameters = parameters;
+  }
+
+  @Test
+  public void test() throws Exception {
+    testForR8(parameters.getBackend())
+        .enableInliningAnnotations()
+        .enableMergeAnnotations()
+        .enableNeverClassInliningAnnotations()
+        .addInnerClasses(NonTargetedMethodTest.class)
+        .addKeepMainRule(Main.class)
+        .setMinApi(parameters.getApiLevel())
+        .run(parameters.getRuntime(), Main.class)
+        .assertSuccessWithOutput(EXPECTED)
+        .inspect(this::checkIsFooPresent);
+  }
+
+  private void checkIsFooPresent(CodeInspector inspector) {
+    ClassSubject classSubject = inspector.clazz(C.class);
+    assertThat(classSubject, isPresent());
+    // TODO(b/150445487): C::foo is not reachable and should be removed.
+    assertThat(classSubject.uniqueMethodWithName("foo"), isPresent());
+  }
+
+  @NeverMerge
+  private static class A {
+    @NeverInline
+    public void foo() {
+      System.out.println("A::foo");
+    }
+  }
+
+  @NeverMerge
+  @NeverClassInline
+  private static class B extends A {
+    // No override of foo, but B::foo will be the only target.
+  }
+
+  @NeverClassInline
+  private static class C extends A {
+
+    // Non-targeted override.
+    @Override
+    public void foo() {
+      System.out.println("C::foo");
+    }
+
+    @NeverInline
+    public void bar() {
+      System.out.println("C::bar");
+    }
+  }
+
+  private static class Main {
+
+    public static void main(String[] args) {
+      new B().foo();
+      new C().bar();
+    }
+  }
+}