Fail Maven build on compiler warnings; remove some warning suppressio…

…ns (#2183)

* Fail Maven build on compiler warnings; remove some warning suppressions

* Fix compiler warnings causing failure for newer JDK

* Improve placement of "raw" and "unchecked" warning suppressions

* Adjust javac documentation link

* Fix compilation error on newer JDKs

extras/src/main/java/com/google/gson/graph/GraphAdapterBuilder.java

@@ -42,7 +42,6 @@
  * Writes a graph of objects as a list of named nodes.
  */
 // TODO: proper documentation
-@SuppressWarnings("rawtypes")
 public final class GraphAdapterBuilder {
   private final Map<Type, InstanceCreator<?>> instanceCreators;
   private final ConstructorConstructor constructorConstructor;
@@ -78,7 +77,7 @@ public void registerOn(GsonBuilder gsonBuilder) {
     }
   }
 
-  static class Factory implements TypeAdapterFactory, InstanceCreator {
+  static class Factory implements TypeAdapterFactory, InstanceCreator<Object> {
     private final Map<Type, InstanceCreator<?>> instanceCreators;
     private final ThreadLocal<Graph> graphThreadLocal = new ThreadLocal<>();
 
@@ -215,7 +214,6 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
      * <p>Gson should only ever call this method when we're expecting it to;
      * that is only when we've called back into Gson to deserialize a tree.
      */
-    @SuppressWarnings("unchecked")
     @Override
     public Object createInstance(Type type) {
       Graph graph = graphThreadLocal.get();
@@ -242,14 +240,14 @@ static class Graph {
      * The queue of elements to write during serialization. Unused during
      * deserialization.
      */
-    private final Queue<Element> queue = new LinkedList<>();
+    private final Queue<Element<?>> queue = new LinkedList<>();
 
     /**
      * The instance currently being deserialized. Used as a backdoor between
      * the graph traversal (which needs to know instances) and instance creators
      * which create them.
      */
-    private Element nextCreate;
+    private Element<Object> nextCreate;
 
     private Graph(Map<Object, Element<?>> map) {
       this.map = map;
@@ -299,11 +297,12 @@ void write(JsonWriter out) throws IOException {
       typeAdapter.write(out, value);
     }
 
+    @SuppressWarnings("unchecked")
     void read(Graph graph) throws IOException {
       if (graph.nextCreate != null) {
         throw new IllegalStateException("Unexpected recursive call to read() for " + id);
       }
-      graph.nextCreate = this;
+      graph.nextCreate = (Element<Object>) this;
       value = typeAdapter.fromJsonTree(element);
       if (value == null) {
         throw new IllegalStateException("non-null value deserialized to null: " + element);

extras/src/test/java/com/google/gson/typeadapters/PostConstructAdapterFactoryTest.java

@@ -16,15 +16,12 @@
 
 package com.google.gson.typeadapters;
 
-import javax.annotation.PostConstruct;
-
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
-
-import junit.framework.TestCase;
-
 import java.util.Arrays;
 import java.util.List;
+import javax.annotation.PostConstruct;
+import junit.framework.TestCase;
 
 public class PostConstructAdapterFactoryTest extends TestCase {
     public void test() throws Exception {
@@ -55,6 +52,7 @@ public void testList() {
         assertEquals(sandwiches, sandwichesFromJson);
     }
 
+    @SuppressWarnings("overrides") // for missing hashCode() override
     static class Sandwich {
         public String bread;
         public String cheese;
@@ -89,6 +87,7 @@ public boolean equals(Object o) {
         }
     }
 
+    @SuppressWarnings("overrides") // for missing hashCode() override
     static class MultipleSandwiches {
         public List<Sandwich> sandwiches;
 

gson/src/main/java/com/google/gson/Gson.java

@@ -503,12 +503,13 @@ private static TypeAdapter<AtomicLongArray> atomicLongArrayAdapter(final TypeAda
    * @throws IllegalArgumentException if this GSON cannot serialize and
    *     deserialize {@code type}.
    */
-  @SuppressWarnings("unchecked")
   public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     Objects.requireNonNull(type, "type must not be null");
     TypeAdapter<?> cached = typeTokenCache.get(type);
     if (cached != null) {
-      return (TypeAdapter<T>) cached;
+      @SuppressWarnings("unchecked")
+      TypeAdapter<T> adapter = (TypeAdapter<T>) cached;
+      return adapter;
     }
 
     Map<TypeToken<?>, FutureTypeAdapter<?>> threadCalls = calls.get();
@@ -520,6 +521,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
     }
 
     // the key and value type parameters always agree
+    @SuppressWarnings("unchecked")
     FutureTypeAdapter<T> ongoingCall = (FutureTypeAdapter<T>) threadCalls.get(type);
     if (ongoingCall != null) {
       return ongoingCall;
@@ -532,6 +534,7 @@ public <T> TypeAdapter<T> getAdapter(TypeToken<T> type) {
       for (TypeAdapterFactory factory : factories) {
         TypeAdapter<T> candidate = factory.create(this, type);
         if (candidate != null) {
+          @SuppressWarnings("unchecked")
           TypeAdapter<T> existingAdapter = (TypeAdapter<T>) typeTokenCache.putIfAbsent(type, candidate);
           // If other thread concurrently added adapter prefer that one instead
           if (existingAdapter != null) {
@@ -780,17 +783,17 @@ public void toJson(Object src, Type typeOfSrc, Appendable writer) throws JsonIOE
    *
    * @throws JsonIOException if there was a problem writing to the writer
    */
-  @SuppressWarnings("unchecked")
   public void toJson(Object src, Type typeOfSrc, JsonWriter writer) throws JsonIOException {
-    TypeAdapter<?> adapter = getAdapter(TypeToken.get(typeOfSrc));
+    @SuppressWarnings("unchecked")
+    TypeAdapter<Object> adapter = (TypeAdapter<Object>) getAdapter(TypeToken.get(typeOfSrc));
     boolean oldLenient = writer.isLenient();
     writer.setLenient(true);
     boolean oldHtmlSafe = writer.isHtmlSafe();
     writer.setHtmlSafe(htmlSafe);
     boolean oldSerializeNulls = writer.getSerializeNulls();
     writer.setSerializeNulls(serializeNulls);
     try {
-      ((TypeAdapter<Object>) adapter).write(writer, src);
+      adapter.write(writer, src);
     } catch (IOException e) {
       throw new JsonIOException(e);
     } catch (AssertionError e) {
@@ -957,12 +960,12 @@ public <T> T fromJson(String json, Class<T> classOfT) throws JsonSyntaxException
    * @throws JsonParseException if json is not a valid representation for an object of type typeOfT
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(String json, Type typeOfT) throws JsonSyntaxException {
     if (json == null) {
       return null;
     }
     StringReader reader = new StringReader(json);
+    @SuppressWarnings("unchecked")
     T target = (T) fromJson(reader, typeOfT);
     return target;
   }
@@ -1017,9 +1020,9 @@ public <T> T fromJson(Reader json, Class<T> classOfT) throws JsonSyntaxException
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    * @since 1.2
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(Reader json, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     JsonReader jsonReader = newJsonReader(json);
+    @SuppressWarnings("unchecked")
     T object = (T) fromJson(jsonReader, typeOfT);
     assertFullConsumption(object, jsonReader);
     return object;
@@ -1052,14 +1055,14 @@ private static void assertFullConsumption(Object obj, JsonReader reader) {
    * @throws JsonIOException if there was a problem writing to the Reader
    * @throws JsonSyntaxException if json is not a valid representation for an object of type
    */
-  @SuppressWarnings("unchecked")
   public <T> T fromJson(JsonReader reader, Type typeOfT) throws JsonIOException, JsonSyntaxException {
     boolean isEmpty = true;
     boolean oldLenient = reader.isLenient();
     reader.setLenient(true);
     try {
       reader.peek();
       isEmpty = false;
+      @SuppressWarnings("unchecked")
       TypeToken<T> typeToken = (TypeToken<T>) TypeToken.get(typeOfT);
       TypeAdapter<T> typeAdapter = getAdapter(typeToken);
       T object = typeAdapter.read(reader);

gson/src/main/java/com/google/gson/GsonBuilder.java

@@ -541,22 +541,23 @@ public GsonBuilder setDateFormat(int dateStyle, int timeStyle) {
    * {@link InstanceCreator}, {@link JsonSerializer}, and a {@link JsonDeserializer} interfaces.
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
    */
-  @SuppressWarnings({"unchecked", "rawtypes"})
   public GsonBuilder registerTypeAdapter(Type type, Object typeAdapter) {
     Objects.requireNonNull(type);
     $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer<?>
         || typeAdapter instanceof JsonDeserializer<?>
         || typeAdapter instanceof InstanceCreator<?>
         || typeAdapter instanceof TypeAdapter<?>);
     if (typeAdapter instanceof InstanceCreator<?>) {
-      instanceCreators.put(type, (InstanceCreator) typeAdapter);
+      instanceCreators.put(type, (InstanceCreator<?>) typeAdapter);
     }
     if (typeAdapter instanceof JsonSerializer<?> || typeAdapter instanceof JsonDeserializer<?>) {
       TypeToken<?> typeToken = TypeToken.get(type);
       factories.add(TreeTypeAdapter.newFactoryWithMatchRawType(typeToken, typeAdapter));
     }
     if (typeAdapter instanceof TypeAdapter<?>) {
-      factories.add(TypeAdapters.newFactory(TypeToken.get(type), (TypeAdapter)typeAdapter));
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapterFactory factory = TypeAdapters.newFactory(TypeToken.get(type), (TypeAdapter)typeAdapter);
+      factories.add(factory);
     }
     return this;
   }
@@ -589,7 +590,6 @@ public GsonBuilder registerTypeAdapterFactory(TypeAdapterFactory factory) {
    * @return a reference to this {@code GsonBuilder} object to fulfill the "Builder" pattern
    * @since 1.7
    */
-  @SuppressWarnings({"unchecked", "rawtypes"})
   public GsonBuilder registerTypeHierarchyAdapter(Class<?> baseType, Object typeAdapter) {
     Objects.requireNonNull(baseType);
     $Gson$Preconditions.checkArgument(typeAdapter instanceof JsonSerializer<?>
@@ -599,7 +599,9 @@ public GsonBuilder registerTypeHierarchyAdapter(Class<?> baseType, Object typeAd
       hierarchyFactories.add(TreeTypeAdapter.newTypeHierarchyFactory(baseType, typeAdapter));
     }
     if (typeAdapter instanceof TypeAdapter<?>) {
-      factories.add(TypeAdapters.newTypeHierarchyFactory(baseType, (TypeAdapter)typeAdapter));
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapterFactory factory = TypeAdapters.newTypeHierarchyFactory(baseType, (TypeAdapter)typeAdapter);
+      factories.add(factory);
     }
     return this;
   }

gson/src/main/java/com/google/gson/internal/LazilyParsedNumber.java

@@ -26,6 +26,7 @@
  *
  * @author Inderjeet Singh
  */
+@SuppressWarnings("serial") // ignore warning about missing serialVersionUID
 public final class LazilyParsedNumber extends Number {
   private final String value;
 

gson/src/main/java/com/google/gson/internal/LinkedTreeMap.java

@@ -38,6 +38,7 @@
  *
  * <p>This implementation was derived from Android 4.1's TreeMap class.
  */
+@SuppressWarnings("serial") // ignore warning about missing serialVersionUID
 public final class LinkedTreeMap<K, V> extends AbstractMap<K, V> implements Serializable {
   @SuppressWarnings({ "unchecked", "rawtypes" }) // to avoid Comparable<Comparable<Comparable<...>>>
   private static final Comparator<Comparable> NATURAL_ORDER = new Comparator<Comparable>() {
@@ -504,10 +505,9 @@ static final class Node<K, V> implements Entry<K, V> {
       return oldValue;
     }
 
-    @SuppressWarnings("rawtypes")
     @Override public boolean equals(Object o) {
       if (o instanceof Entry) {
-        Entry other = (Entry) o;
+        Entry<?, ?> other = (Entry<?, ?>) o;
         return (key == null ? other.getKey() == null : key.equals(other.getKey()))
             && (value == null ? other.getValue() == null : value.equals(other.getValue()));
       }

gson/src/main/java/com/google/gson/internal/bind/ArrayTypeAdapter.java

@@ -35,7 +35,6 @@
  */
 public final class ArrayTypeAdapter<E> extends TypeAdapter<Object> {
   public static final TypeAdapterFactory FACTORY = new TypeAdapterFactory() {
-    @SuppressWarnings({"unchecked", "rawtypes"})
     @Override public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
       Type type = typeToken.getType();
       if (!(type instanceof GenericArrayType || type instanceof Class && ((Class<?>) type).isArray())) {
@@ -44,8 +43,11 @@ public final class ArrayTypeAdapter<E> extends TypeAdapter<Object> {
 
       Type componentType = $Gson$Types.getArrayComponentType(type);
       TypeAdapter<?> componentTypeAdapter = gson.getAdapter(TypeToken.get(componentType));
-      return new ArrayTypeAdapter(
+
+      @SuppressWarnings({"unchecked", "rawtypes"})
+      TypeAdapter<T> arrayAdapter = new ArrayTypeAdapter(
               gson, componentTypeAdapter, $Gson$Types.getRawType(componentType));
+      return arrayAdapter;
     }
   };
 
@@ -89,7 +91,6 @@ public ArrayTypeAdapter(Gson context, TypeAdapter<E> componentTypeAdapter, Class
     }
   }
 
-  @SuppressWarnings("unchecked")
   @Override public void write(JsonWriter out, Object array) throws IOException {
     if (array == null) {
       out.nullValue();
@@ -98,6 +99,7 @@ public ArrayTypeAdapter(Gson context, TypeAdapter<E> componentTypeAdapter, Class
 
     out.beginArray();
     for (int i = 0, length = Array.getLength(array); i < length; i++) {
+      @SuppressWarnings("unchecked")
       E value = (E) Array.get(array, i);
       componentTypeAdapter.write(out, value);
     }

gson/src/main/java/com/google/gson/internal/bind/JsonAdapterAnnotationTypeAdapterFactory.java

@@ -38,7 +38,7 @@ public JsonAdapterAnnotationTypeAdapterFactory(ConstructorConstructor constructo
     this.constructorConstructor = constructorConstructor;
   }
 
-  @SuppressWarnings("unchecked")
+  @SuppressWarnings("unchecked") // this is not safe; requires that user has specified correct adapter class for @JsonAdapter
   @Override
   public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> targetType) {
     Class<? super T> rawType = targetType.getRawType();
@@ -49,7 +49,6 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> targetType) {
     return (TypeAdapter<T>) getTypeAdapter(constructorConstructor, gson, targetType, annotation);
   }
 
-  @SuppressWarnings({ "unchecked", "rawtypes" }) // Casts guarded by conditionals.
   TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gson gson,
       TypeToken<?> type, JsonAdapter annotation) {
     Object instance = constructorConstructor.get(TypeToken.get(annotation.value())).construct();
@@ -62,12 +61,16 @@ TypeAdapter<?> getTypeAdapter(ConstructorConstructor constructorConstructor, Gso
       typeAdapter = ((TypeAdapterFactory) instance).create(gson, type);
     } else if (instance instanceof JsonSerializer || instance instanceof JsonDeserializer) {
       JsonSerializer<?> serializer = instance instanceof JsonSerializer
-          ? (JsonSerializer) instance
+          ? (JsonSerializer<?>) instance
           : null;
       JsonDeserializer<?> deserializer = instance instanceof JsonDeserializer
-          ? (JsonDeserializer) instance
+          ? (JsonDeserializer<?>) instance
           : null;
-      typeAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null, nullSafe);
+
+      @SuppressWarnings({ "unchecked", "rawtypes" })
+      TypeAdapter<?> tempAdapter = new TreeTypeAdapter(serializer, deserializer, gson, type, null, nullSafe);
+      typeAdapter = tempAdapter;
+
       nullSafe = false;
     } else {
       throw new IllegalArgumentException("Invalid attempt to bind an instance of "

gson/src/main/java/com/google/gson/internal/bind/ObjectTypeAdapter.java

@@ -166,13 +166,13 @@ private Object readTerminal(JsonReader in, JsonToken peeked) throws IOException
     }
   }
 
-  @SuppressWarnings("unchecked")
   @Override public void write(JsonWriter out, Object value) throws IOException {
     if (value == null) {
       out.nullValue();
       return;
     }
 
+    @SuppressWarnings("unchecked")
     TypeAdapter<Object> typeAdapter = (TypeAdapter<Object>) gson.getAdapter(value.getClass());
     if (typeAdapter instanceof ObjectTypeAdapter) {
       out.beginObject();

gson/src/main/java/com/google/gson/internal/bind/ReflectiveTypeAdapterFactory.java

@@ -126,19 +126,19 @@ private ReflectiveTypeAdapterFactory.BoundField createBoundField(
       final TypeToken<?> fieldType, boolean serialize, boolean deserialize,
       final boolean blockInaccessible) {
     final boolean isPrimitive = Primitives.isPrimitive(fieldType.getRawType());
-    // special casing primitives here saves ~5% on Android...
     JsonAdapter annotation = field.getAnnotation(JsonAdapter.class);
     TypeAdapter<?> mapped = null;
     if (annotation != null) {
+      // This is not safe; requires that user has specified correct adapter class for @JsonAdapter
       mapped = jsonAdapterFactory.getTypeAdapter(
           constructorConstructor, context, fieldType, annotation);
     }
     final boolean jsonAdapterPresent = mapped != null;
     if (mapped == null) mapped = context.getAdapter(fieldType);
 
-    final TypeAdapter<?> typeAdapter = mapped;
+    @SuppressWarnings("unchecked")
+    final TypeAdapter<Object> typeAdapter = (TypeAdapter<Object>) mapped;
     return new ReflectiveTypeAdapterFactory.BoundField(name, serialize, deserialize) {
-      @SuppressWarnings({"unchecked", "rawtypes"}) // the type adapter and field type always agree
       @Override void write(JsonWriter writer, Object value)
           throws IOException, IllegalAccessException {
         if (!serialized) return;
@@ -152,8 +152,8 @@ private ReflectiveTypeAdapterFactory.BoundField createBoundField(
           return;
         }
         writer.name(name);
-        TypeAdapter t = jsonAdapterPresent ? typeAdapter
-            : new TypeAdapterRuntimeTypeWrapper(context, typeAdapter, fieldType.getType());
+        TypeAdapter<Object> t = jsonAdapterPresent ? typeAdapter
+            : new TypeAdapterRuntimeTypeWrapper<>(context, typeAdapter, fieldType.getType());
         t.write(writer, fieldValue);
       }
       @Override void read(JsonReader reader, Object value)