Test for private interface methods in nests.

Bug: 191115349
Change-Id: I61cb305f92b27fe263a124f2c11d4b6840d381cf

src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/NestPrivateInterfaceMethodsTest.java

diff --git a/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/NestPrivateInterfaceMethodsTest.java b/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/NestPrivateInterfaceMethodsTest.java
new file mode 100644
index 0000000..ae2b6ae
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/NestPrivateInterfaceMethodsTest.java
@@ -0,0 +1,78 @@
+// 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.desugar.nestaccesscontrol;
+
+import com.android.tools.r8.DesugarTestConfiguration;
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.TestParametersCollection;
+import com.android.tools.r8.TestRuntime.CfVm;
+import com.android.tools.r8.utils.StringUtils;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+@RunWith(Parameterized.class)
+public class NestPrivateInterfaceMethodsTest extends TestBase {
+
+  static final String EXPECTED = StringUtils.lines("Hello world!");
+
+  private final TestParameters parameters;
+
+  @Parameterized.Parameters(name = "{0}")
+  public static TestParametersCollection data() {
+    return getTestParameters().withAllRuntimes().withAllApiLevelsAlsoForCf().build();
+  }
+
+  public NestPrivateInterfaceMethodsTest(TestParameters parameters) {
+    this.parameters = parameters;
+  }
+
+  private byte[] getClassWithNest(Class<?> clazz) throws Exception {
+    return transformer(clazz)
+        .setNest(I.class, J.class)
+        .setAccessFlags(
+            I.class.getMethod("foo"),
+            flags -> {
+              flags.unsetPublic();
+              flags.setPrivate();
+            })
+        .transform();
+  }
+
+  @Test
+  public void test() throws Exception {
+    testForDesugaring(parameters)
+        .addProgramClasses(TestClass.class)
+        .addProgramClassFileData(getClassWithNest(I.class), getClassWithNest(J.class))
+        .run(parameters.getRuntime(), TestClass.class)
+        // TODO(191115349): Nest desugar does not downgrade the classfile version.
+        .applyIf(
+            c ->
+                DesugarTestConfiguration.isNotJavac(c)
+                    || parameters.getRuntime().asCf().isNewerThanOrEqual(CfVm.JDK11),
+            r -> r.assertSuccessWithOutput(EXPECTED),
+            r -> r.assertFailureWithErrorThatThrows(UnsupportedClassVersionError.class));
+  }
+
+  interface I {
+    default /* will be private */ void foo() {
+      System.out.println("Hello world!");
+    }
+  }
+
+  interface J {
+    default void bar(I o) {
+      o.foo();
+    }
+  }
+
+  static class TestClass implements I, J {
+
+    public static void main(String[] args) {
+      TestClass o = new TestClass();
+      o.bar(o);
+    }
+  }
+}