Add more CheckReturnValues for JsonReader.

This encourages skipName over nextName.

moshi/src/main/java/com/squareup/moshi/JsonReader.java

@@ -312,25 +312,25 @@ public abstract class JsonReader implements Closeable {
   /**
    * Returns true if the current array or object has another element.
    */
-  public abstract boolean hasNext() throws IOException;
+  @CheckReturnValue public abstract boolean hasNext() throws IOException;
 
   /**
    * Returns the type of the next token without consuming it.
    */
-  public abstract Token peek() throws IOException;
+  @CheckReturnValue public abstract Token peek() throws IOException;
 
   /**
    * Returns the next token, a {@linkplain Token#NAME property name}, and consumes it.
    *
    * @throws JsonDataException if the next token in the stream is not a property name.
    */
-  public abstract String nextName() throws IOException;
+  @CheckReturnValue public abstract String nextName() throws IOException;
 
   /**
    * If the next token is a {@linkplain Token#NAME property name} that's in {@code options}, this
    * consumes it and returns its index. Otherwise this returns -1 and no name is consumed.
    */
-  public abstract int selectName(Options options) throws IOException;
+  @CheckReturnValue public abstract int selectName(Options options) throws IOException;
 
   /**
    * Skips the next token, consuming it. This method is intended for use when the JSON token stream
@@ -353,7 +353,7 @@ public abstract class JsonReader implements Closeable {
    * If the next token is a {@linkplain Token#STRING string} that's in {@code options}, this
    * consumes it and returns its index. Otherwise this returns -1 and no string is consumed.
    */
-  public abstract int selectString(Options options) throws IOException;
+  @CheckReturnValue public abstract int selectString(Options options) throws IOException;
 
   /**
    * Returns the {@linkplain Token#BOOLEAN boolean} value of the next token, consuming it.

moshi/src/test/java/com/squareup/moshi/JsonReaderPathTest.java

@@ -35,6 +35,7 @@ public final class JsonReaderPathTest {
     return JsonCodecFactory.factories();
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void path() throws IOException {
     JsonReader reader = factory.newReader("{\"a\":[2,true,false,null,\"b\",{\"c\":\"d\"},[3]]}");
     assertThat(reader.getPath()).isEqualTo("$");
@@ -114,6 +115,7 @@ public final class JsonReaderPathTest {
     assertThat(reader.getPath()).isEqualTo("$");
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void objectPath() throws IOException {
     JsonReader reader = factory.newReader("{\"a\":1,\"b\":2}");
     assertThat(reader.getPath()).isEqualTo("$");
@@ -154,6 +156,7 @@ public final class JsonReaderPathTest {
     assertThat(reader.getPath()).isEqualTo("$");
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void arrayPath() throws IOException {
     JsonReader reader = factory.newReader("[1,2]");
     assertThat(reader.getPath()).isEqualTo("$");
@@ -212,6 +215,7 @@ public final class JsonReaderPathTest {
     assertThat(reader.getPath()).isEqualTo("$.null");
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void skipObjectValues() throws IOException {
     JsonReader reader = factory.newReader("{\"a\":1,\"b\":2}");
     reader.beginObject();

moshi/src/test/java/com/squareup/moshi/JsonUtf8ReaderTest.java

@@ -393,6 +393,7 @@ public final class JsonUtf8ReaderTest {
     }
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void prematurelyClosed() throws IOException {
     try {
       JsonReader reader = newReader("{\"a\":[]}");
@@ -977,6 +978,7 @@ public final class JsonUtf8ReaderTest {
     }
   }
 
+  @SuppressWarnings("CheckReturnValue")
   @Test public void failWithPositionDeepPath() throws IOException {
     JsonReader reader = newReader("[1,{\"a\":[2,3,}");
     reader.beginArray();