Fix constructor bug with compat mode

Bug: 165000217
Change-Id: Ica5c62bb62d2736b75ab500c12d1079d066d79a7
diff --git a/src/main/java/com/android/tools/r8/horizontalclassmerging/ConstructorMerger.java b/src/main/java/com/android/tools/r8/horizontalclassmerging/ConstructorMerger.java
index 8ffb694..b6f3058 100644
--- a/src/main/java/com/android/tools/r8/horizontalclassmerging/ConstructorMerger.java
+++ b/src/main/java/com/android/tools/r8/horizontalclassmerging/ConstructorMerger.java
@@ -91,6 +91,10 @@
 
     DexEncodedMethod encodedMethod = constructor.toTypeSubstitutedMethod(method);
     encodedMethod.getMutableOptimizationInfo().markForceInline();
+    encodedMethod.accessFlags.unsetConstructor();
+    encodedMethod.accessFlags.unsetPublic();
+    encodedMethod.accessFlags.unsetProtected();
+    encodedMethod.accessFlags.setPrivate();
     target.addDirectMethod(encodedMethod);
     return method;
   }
diff --git a/src/test/java/com/android/tools/r8/classmerging/horizontal/CompatKeepConstructorLiveTest.java b/src/test/java/com/android/tools/r8/classmerging/horizontal/CompatKeepConstructorLiveTest.java
new file mode 100644
index 0000000..9ccc2d4
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/classmerging/horizontal/CompatKeepConstructorLiveTest.java
@@ -0,0 +1,62 @@
+// 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.classmerging.horizontal;
+
+import static com.android.tools.r8.utils.codeinspector.Matchers.isPresent;
+import static com.android.tools.r8.utils.codeinspector.Matchers.notIf;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import com.android.tools.r8.NeverClassInline;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.utils.codeinspector.ClassSubject;
+import org.junit.Test;
+
+public class CompatKeepConstructorLiveTest extends HorizontalClassMergingTestBase {
+  public CompatKeepConstructorLiveTest(
+      TestParameters parameters, boolean enableHorizontalClassMerging) {
+    super(parameters, enableHorizontalClassMerging);
+  }
+
+  @Test
+  public void testR8() throws Exception {
+    testForR8Compat(parameters.getBackend())
+        .addInnerClasses(getClass())
+        .addKeepMainRule(Main.class)
+        .addOptionsModification(
+            options -> options.enableHorizontalClassMerging = enableHorizontalClassMerging)
+        .enableNeverClassInliningAnnotations()
+        .setMinApi(parameters.getApiLevel())
+        .run(parameters.getRuntime(), Main.class)
+        .assertSuccessWithOutputLines("b: main", "true")
+        .inspect(
+            codeInspector -> {
+              ClassSubject aClassSubject = codeInspector.clazz(A.class);
+              assertThat(aClassSubject, isPresent());
+
+              assertThat(aClassSubject.init(), isPresent());
+
+              assertThat(codeInspector.clazz(A.class), isPresent());
+              assertThat(
+                  codeInspector.clazz(B.class), notIf(isPresent(), enableHorizontalClassMerging));
+            });
+  }
+
+  @NeverClassInline
+  public static class A {}
+
+  @NeverClassInline
+  public static class B {
+    public B(String v) {
+      System.out.println("b: " + v);
+    }
+  }
+
+  public static class Main {
+    public static void main(String[] args) throws Exception {
+      new B("main");
+      System.out.println(A.class.toString().length() > 0);
+    }
+  }
+}
diff --git a/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/Java11R8CompilationTest.java b/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/Java11R8CompilationTest.java
index 762916e..e1d892d 100644
--- a/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/Java11R8CompilationTest.java
+++ b/src/test/java/com/android/tools/r8/desugar/nestaccesscontrol/Java11R8CompilationTest.java
@@ -47,6 +47,7 @@
 
   @Test
   public void testR8CompiledWithR8() throws Exception {
+    expectThrowsWithHorizontalClassMerging();
     testForR8(parameters.getBackend())
         .setMinApi(parameters.getApiLevel())
         .addProgramFiles(ToolHelper.R8_WITH_RELOCATED_DEPS_11_JAR)
diff --git a/src/test/java/com/android/tools/r8/kotlin/lambda/KotlinLambdaMergingTest.java b/src/test/java/com/android/tools/r8/kotlin/lambda/KotlinLambdaMergingTest.java
index b624956..2498467 100644
--- a/src/test/java/com/android/tools/r8/kotlin/lambda/KotlinLambdaMergingTest.java
+++ b/src/test/java/com/android/tools/r8/kotlin/lambda/KotlinLambdaMergingTest.java
@@ -302,7 +302,6 @@
 
   @Test
   public void testTrivialKs() throws Exception {
-    expectThrowsWithHorizontalClassMergingIf(allowAccessModification);
     final String mainClassName = "lambdas_kstyle_trivial.MainKt";
     runTest(
         "lambdas_kstyle_trivial",
@@ -384,7 +383,6 @@
 
   @Test
   public void testGenericsNoSignatureKs() throws Exception {
-    expectThrowsWithHorizontalClassMerging();
     final String mainClassName = "lambdas_kstyle_generics.MainKt";
     runTest(
         "lambdas_kstyle_generics",
@@ -413,7 +411,6 @@
 
   @Test
   public void testInnerClassesAndEnclosingMethodsKs() throws Exception {
-    expectThrowsWithHorizontalClassMerging();
     final String mainClassName = "lambdas_kstyle_generics.MainKt";
     runTest(
         "lambdas_kstyle_generics",
@@ -445,7 +442,6 @@
 
   @Test
   public void testGenericsSignatureInnerEnclosingKs() throws Exception {
-    expectThrowsWithHorizontalClassMerging();
     final String mainClassName = "lambdas_kstyle_generics.MainKt";
     runTest(
         "lambdas_kstyle_generics",
@@ -479,7 +475,6 @@
 
   @Test
   public void testTrivialJs() throws Exception {
-    expectThrowsWithHorizontalClassMergingIf(allowAccessModification);
     final String mainClassName = "lambdas_jstyle_trivial.MainKt";
     runTest(
         "lambdas_jstyle_trivial",
@@ -529,7 +524,6 @@
 
   @Test
   public void testSingleton() throws Exception {
-    expectThrowsWithHorizontalClassMergingIf(allowAccessModification);
     final String mainClassName = "lambdas_singleton.MainKt";
     runTest(
         "lambdas_singleton",