Hide ExpectationGatherer.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=164284459

core/src/main/java/com/google/common/truth/Expect.java

@@ -30,7 +30,15 @@
 import org.junit.runners.model.Statement;
 
 @GwtIncompatible("JUnit4")
-public class Expect extends TestVerb implements TestRule {
+public final class Expect extends TestVerb implements TestRule {
+  /**
+   * @deprecated To provide your own failure handling, use {@code new TestVerb(new
+   *     AbstractFailureStrategy() { ... })} instead of {@code Expect.create(new
+   *     ExpectationGatherer() { ... })}. Or, if you're testing that assertions on a custom {@code
+   *     Subject} fail (using {@code ExpectationGatherer} to capture the failures), use {@link
+   *     ExpectFailure}.
+   */
+  @Deprecated
   public static class ExpectationGatherer extends AbstractFailureStrategy {
     private final List<ExpectationFailure> messages = new ArrayList<ExpectationFailure>();
     private final boolean showStackTrace;
@@ -131,6 +139,12 @@ public static Expect create() {
     return create(new ExpectationGatherer());
   }
 
+  /**
+   * @deprecated To provide your own failure handling, use {@code new TestVerb(new
+   *     AbstractFailureStrategy() { ... })} instead of {@code Expect.create(new
+   *     ExpectationGatherer() { ... })}.
+   */
+  @Deprecated
   public static Expect create(ExpectationGatherer gatherer) {
     return new Expect(gatherer);
   }

core/src/test/java/com/google/common/truth/ExpectFailureWithStackTraceTest.java

@@ -17,9 +17,9 @@
 
 import static com.google.common.truth.Truth.assertThat;
 
-import com.google.common.truth.Expect.ExpectationGatherer;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.TestRule;
 import org.junit.runner.Description;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -30,25 +30,21 @@
 public class ExpectFailureWithStackTraceTest {
   private static final String METHOD_NAME = "ExpectFailureWithStackTraceTest.expectTwoFailures";
 
-  @Rule
-  public final Expect failToExpect =
-      new FailingExpect(new ExpectationGatherer(true /* showStackTrace */));
+  @Rule public final FailingExpect failToExpect = new FailingExpect();
 
   @Test
   public void expectTwoFailures() {
-    failToExpect.that(4).isNotEqualTo(4);
-    failToExpect.that("abc").contains("x");
+    failToExpect.delegate.that(4).isNotEqualTo(4);
+    failToExpect.delegate.that("abc").contains("x");
   }
 
   /** Expect class that can examine the error message */
-  public static class FailingExpect extends Expect {
-    protected FailingExpect(ExpectationGatherer gatherer) {
-      super(gatherer);
-    }
+  public static class FailingExpect implements TestRule {
+    final Expect delegate = Expect.createAndEnableStackTrace();
 
     @Override
     public Statement apply(Statement base, Description description) {
-      final Statement s = super.apply(base, description);
+      final Statement s = delegate.apply(base, description);
       return new Statement() {
         @Override
         public void evaluate() throws Throwable {