Import Gson's type resolver.

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

@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2008 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+
+/**
+ * Represents a generic type {@code T}. Java doesn't yet provide a way to represent generic types,
+ * so this class does. Forces clients to create a subclass of this class which enables retrieval the
+ * type information even at runtime.
+ *
+ * <p>For example, to create a type literal for {@code List<String>}, you can create an empty
+ * anonymous inner class: <pre>   {@code
+ *
+ *   TypeToken<List<String>> list = new TypeToken<List<String>>() {};
+ * }</pre>
+ *
+ * <p>This syntax cannot be used to create type literals that have wildcard parameters, such as
+ * {@code Class<?>} or {@code List<? extends CharSequence>}.
+ *
+ * @author Bob Lee
+ * @author Sven Mawson
+ * @author Jesse Wilson
+ */
+public class TypeLiteral<T> {
+  final Class<? super T> rawType;
+  final Type type;
+  final int hashCode;
+
+  /**
+   * Constructs a new type literal. Derives represented class from type parameter.
+   *
+   * <p>Clients create an empty anonymous subclass. Doing so embeds the type parameter in the
+   * anonymous class's type hierarchy so we can reconstitute it at runtime despite erasure.
+   */
+  @SuppressWarnings("unchecked")
+  protected TypeLiteral() {
+    this.type = getSuperclassTypeParameter(getClass());
+    this.rawType = (Class<? super T>) Types.getRawType(type);
+    this.hashCode = type.hashCode();
+  }
+
+  /** Unsafe. Constructs a type literal manually. */
+  @SuppressWarnings("unchecked")
+  TypeLiteral(Type type) {
+    if (type == null) throw new NullPointerException("type == null");
+    this.type = Types.canonicalize(type);
+    this.rawType = (Class<? super T>) Types.getRawType(this.type);
+    this.hashCode = this.type.hashCode();
+  }
+
+  /** Returns the type from super class's type parameter in canonical for}. */
+  static Type getSuperclassTypeParameter(Class<?> subclass) {
+    Type superclass = subclass.getGenericSuperclass();
+    if (superclass instanceof Class) throw new IllegalArgumentException("Missing type parameter.");
+    ParameterizedType parameterized = (ParameterizedType) superclass;
+    return Types.canonicalize(parameterized.getActualTypeArguments()[0]);
+  }
+
+  /** Returns the raw (non-generic) type for this type literal. */
+  public final Class<? super T> getRawType() {
+    return rawType;
+  }
+
+  public final Type getType() {
+    return type;
+  }
+
+  @Override public final int hashCode() {
+    return this.hashCode;
+  }
+
+  @Override public final boolean equals(Object o) {
+    return o instanceof TypeLiteral<?>
+        && Types.equals(type, ((TypeLiteral<?>) o).type);
+  }
+
+  @Override public final String toString() {
+    return Types.typeToString(type);
+  }
+
+  /** Returns a type literal for {@code type}. */
+  public static TypeLiteral<?> get(Type type) {
+    return new TypeLiteral<Object>(type);
+  }
+
+  /** Returns a type literal for {@code type}. */
+  public static <T> TypeLiteral<T> get(Class<T> type) {
+    return new TypeLiteral<T>(type);
+  }
+}

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

@@ -0,0 +1,542 @@
+/**
+ * Copyright (C) 2008 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi;
+
+import java.lang.reflect.Array;
+import java.lang.reflect.GenericArrayType;
+import java.lang.reflect.GenericDeclaration;
+import java.lang.reflect.Modifier;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.lang.reflect.TypeVariable;
+import java.lang.reflect.WildcardType;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Properties;
+
+/**
+ * Static methods for working with types.
+ *
+ * @author Bob Lee
+ * @author Jesse Wilson
+ */
+final class Types {
+  static final Type[] EMPTY_TYPE_ARRAY = new Type[] {};
+
+  private Types() {
+  }
+
+  /**
+   * Returns a new parameterized type, applying {@code typeArguments} to {@code rawType} and
+   * enclosed by {@code ownerType}.
+   */
+  public static ParameterizedType newParameterizedTypeWithOwner(
+      Type ownerType, Type rawType, Type... typeArguments) {
+    return new ParameterizedTypeImpl(ownerType, rawType, typeArguments);
+  }
+
+  /** Returns an array type whose elements are all instances of {@code componentType}. */
+  public static GenericArrayType arrayOf(Type componentType) {
+    return new GenericArrayTypeImpl(componentType);
+  }
+
+  /**
+   * Returns a type that represents an unknown type that extends {@code bound}. For example, if
+   * {@code bound} is {@code CharSequence.class}, this returns {@code ? extends CharSequence}. If
+   * {@code bound} is {@code Object.class}, this returns {@code ?}, which is shorthand for {@code
+   * ? extends Object}.
+   */
+  public static WildcardType subtypeOf(Type bound) {
+    return new WildcardTypeImpl(new Type[] { bound }, EMPTY_TYPE_ARRAY);
+  }
+
+  /**
+   * Returns a type that represents an unknown supertype of {@code bound}. For example, if {@code
+   * bound} is {@code String.class}, this returns {@code ? super String}.
+   */
+  public static WildcardType supertypeOf(Type bound) {
+    return new WildcardTypeImpl(new Type[] { Object.class }, new Type[] { bound });
+  }
+
+  /**
+   * Returns a type that is functionally equal but not necessarily equal according to {@link
+   * Object#equals(Object) Object.equals()}.
+   */
+  public static Type canonicalize(Type type) {
+    if (type instanceof Class) {
+      Class<?> c = (Class<?>) type;
+      return c.isArray() ? new GenericArrayTypeImpl(canonicalize(c.getComponentType())) : c;
+
+    } else if (type instanceof ParameterizedType) {
+      ParameterizedType p = (ParameterizedType) type;
+      return new ParameterizedTypeImpl(p.getOwnerType(),
+          p.getRawType(), p.getActualTypeArguments());
+
+    } else if (type instanceof GenericArrayType) {
+      GenericArrayType g = (GenericArrayType) type;
+      return new GenericArrayTypeImpl(g.getGenericComponentType());
+
+    } else if (type instanceof WildcardType) {
+      WildcardType w = (WildcardType) type;
+      return new WildcardTypeImpl(w.getUpperBounds(), w.getLowerBounds());
+
+    } else {
+      return type; // This type is unsupported!
+    }
+  }
+
+  public static Class<?> getRawType(Type type) {
+    if (type instanceof Class<?>) {
+      // type is a normal class.
+      return (Class<?>) type;
+
+    } else if (type instanceof ParameterizedType) {
+      ParameterizedType parameterizedType = (ParameterizedType) type;
+
+      // I'm not exactly sure why getRawType() returns Type instead of Class. Neal isn't either but
+      // suspects some pathological case related to nested classes exists.
+      Type rawType = parameterizedType.getRawType();
+      return (Class<?>) rawType;
+
+    } else if (type instanceof GenericArrayType) {
+      Type componentType = ((GenericArrayType)type).getGenericComponentType();
+      return Array.newInstance(getRawType(componentType), 0).getClass();
+
+    } else if (type instanceof TypeVariable) {
+      // We could use the variable's bounds, but that won't work if there are multiple. having a raw
+      // type that's more general than necessary is okay.
+      return Object.class;
+
+    } else if (type instanceof WildcardType) {
+      return getRawType(((WildcardType) type).getUpperBounds()[0]);
+
+    } else {
+      String className = type == null ? "null" : type.getClass().getName();
+      throw new IllegalArgumentException("Expected a Class, ParameterizedType, or "
+          + "GenericArrayType, but <" + type + "> is of type " + className);
+    }
+  }
+
+  static boolean equal(Object a, Object b) {
+    return a == b || (a != null && a.equals(b));
+  }
+
+  /** Returns true if {@code a} and {@code b} are equal. */
+  public static boolean equals(Type a, Type b) {
+    if (a == b) {
+      return true; // Also handles (a == null && b == null).
+
+    } else if (a instanceof Class) {
+      return a.equals(b); // Class already specifies equals().
+
+    } else if (a instanceof ParameterizedType) {
+      if (!(b instanceof ParameterizedType)) return false;
+      ParameterizedType pa = (ParameterizedType) a;
+      ParameterizedType pb = (ParameterizedType) b;
+      Type[] aTypeArguments = pa instanceof ParameterizedTypeImpl
+          ? ((ParameterizedTypeImpl) pa).typeArguments
+          : pa.getActualTypeArguments();
+      Type[] bTypeArguments = pb instanceof ParameterizedTypeImpl
+          ? ((ParameterizedTypeImpl) pb).typeArguments
+          : pb.getActualTypeArguments();
+      return equal(pa.getOwnerType(), pb.getOwnerType())
+          && pa.getRawType().equals(pb.getRawType())
+          && Arrays.equals(aTypeArguments, bTypeArguments);
+
+    } else if (a instanceof GenericArrayType) {
+      if (!(b instanceof GenericArrayType)) return false;
+      GenericArrayType ga = (GenericArrayType) a;
+      GenericArrayType gb = (GenericArrayType) b;
+      return equals(ga.getGenericComponentType(), gb.getGenericComponentType());
+
+    } else if (a instanceof WildcardType) {
+      if (!(b instanceof WildcardType)) return false;
+      WildcardType wa = (WildcardType) a;
+      WildcardType wb = (WildcardType) b;
+      return Arrays.equals(wa.getUpperBounds(), wb.getUpperBounds())
+          && Arrays.equals(wa.getLowerBounds(), wb.getLowerBounds());
+
+    } else if (a instanceof TypeVariable) {
+      if (!(b instanceof TypeVariable)) return false;
+      TypeVariable<?> va = (TypeVariable<?>) a;
+      TypeVariable<?> vb = (TypeVariable<?>) b;
+      return va.getGenericDeclaration() == vb.getGenericDeclaration()
+          && va.getName().equals(vb.getName());
+
+    } else {
+      // This isn't a supported type. Could be a generic array type, wildcard type, etc.
+      return false;
+    }
+  }
+
+  private static int hashCodeOrZero(Object o) {
+    return o != null ? o.hashCode() : 0;
+  }
+
+  public static String typeToString(Type type) {
+    return type instanceof Class ? ((Class<?>) type).getName() : type.toString();
+  }
+
+  /**
+   * Returns the generic supertype for {@code supertype}. For example, given a class {@code
+   * IntegerSet}, the result for when supertype is {@code Set.class} is {@code Set<Integer>} and the
+   * result when the supertype is {@code Collection.class} is {@code Collection<Integer>}.
+   */
+  static Type getGenericSupertype(Type context, Class<?> rawType, Class<?> toResolve) {
+    if (toResolve == rawType) {
+      return context;
+    }
+
+    // we skip searching through interfaces if unknown is an interface
+    if (toResolve.isInterface()) {
+      Class<?>[] interfaces = rawType.getInterfaces();
+      for (int i = 0, length = interfaces.length; i < length; i++) {
+        if (interfaces[i] == toResolve) {
+          return rawType.getGenericInterfaces()[i];
+        } else if (toResolve.isAssignableFrom(interfaces[i])) {
+          return getGenericSupertype(rawType.getGenericInterfaces()[i], interfaces[i], toResolve);
+        }
+      }
+    }
+
+    // check our supertypes
+    if (!rawType.isInterface()) {
+      while (rawType != Object.class) {
+        Class<?> rawSupertype = rawType.getSuperclass();
+        if (rawSupertype == toResolve) {
+          return rawType.getGenericSuperclass();
+        } else if (toResolve.isAssignableFrom(rawSupertype)) {
+          return getGenericSupertype(rawType.getGenericSuperclass(), rawSupertype, toResolve);
+        }
+        rawType = rawSupertype;
+      }
+    }
+
+    // we can't resolve this further
+    return toResolve;
+  }
+
+  /**
+   * Returns the generic form of {@code supertype}. For example, if this is {@code
+   * ArrayList<String>}, this returns {@code Iterable<String>} given the input {@code
+   * Iterable.class}.
+   *
+   * @param supertype a superclass of, or interface implemented by, this.
+   */
+  static Type getSupertype(Type context, Class<?> contextRawType, Class<?> supertype) {
+    if (!supertype.isAssignableFrom(contextRawType)) throw new IllegalArgumentException();
+    return resolve(context, contextRawType,
+        getGenericSupertype(context, contextRawType, supertype));
+  }
+
+  /**
+   * Returns the component type of this array type.
+   * @throws ClassCastException if this type is not an array.
+   */
+  public static Type arrayComponentType(Type array) {
+    return array instanceof GenericArrayType
+        ? ((GenericArrayType) array).getGenericComponentType()
+        : ((Class<?>) array).getComponentType();
+  }
+
+  /**
+   * Returns the element type of this collection type.
+   * @throws IllegalArgumentException if this type is not a collection.
+   */
+  public static Type collectionElementType(Type context, Class<?> contextRawType) {
+    Type collectionType = getSupertype(context, contextRawType, Collection.class);
+
+    if (collectionType instanceof WildcardType) {
+      collectionType = ((WildcardType) collectionType).getUpperBounds()[0];
+    }
+    if (collectionType instanceof ParameterizedType) {
+      return ((ParameterizedType) collectionType).getActualTypeArguments()[0];
+    }
+    return Object.class;
+  }
+
+  /**
+   * Returns a two element array containing this map's key and value types in positions 0 and 1
+   * respectively.
+   */
+  public static Type[] mapKeyAndValueTypes(Type context, Class<?> contextRawType) {
+    // Work around a problem with the declaration of java.util.Properties. That class should extend
+    // Hashtable<String, String>, but it's declared to extend Hashtable<Object, Object>.
+    if (context == Properties.class) return new Type[] { String.class, String.class };
+
+    Type mapType = getSupertype(context, contextRawType, Map.class);
+    if (mapType instanceof ParameterizedType) {
+      ParameterizedType mapParameterizedType = (ParameterizedType) mapType;
+      return mapParameterizedType.getActualTypeArguments();
+    }
+    return new Type[] { Object.class, Object.class };
+  }
+
+  public static Type resolve(Type context, Class<?> contextRawType, Type toResolve) {
+    // This implementation is made a little more complicated in an attempt to avoid object-creation.
+    while (true) {
+      if (toResolve instanceof TypeVariable) {
+        TypeVariable<?> typeVariable = (TypeVariable<?>) toResolve;
+        toResolve = resolveTypeVariable(context, contextRawType, typeVariable);
+        if (toResolve == typeVariable) return toResolve;
+
+      } else if (toResolve instanceof Class && ((Class<?>) toResolve).isArray()) {
+        Class<?> original = (Class<?>) toResolve;
+        Type componentType = original.getComponentType();
+        Type newComponentType = resolve(context, contextRawType, componentType);
+        return componentType == newComponentType
+            ? original
+            : arrayOf(newComponentType);
+
+      } else if (toResolve instanceof GenericArrayType) {
+        GenericArrayType original = (GenericArrayType) toResolve;
+        Type componentType = original.getGenericComponentType();
+        Type newComponentType = resolve(context, contextRawType, componentType);
+        return componentType == newComponentType
+            ? original
+            : arrayOf(newComponentType);
+
+      } else if (toResolve instanceof ParameterizedType) {
+        ParameterizedType original = (ParameterizedType) toResolve;
+        Type ownerType = original.getOwnerType();
+        Type newOwnerType = resolve(context, contextRawType, ownerType);
+        boolean changed = newOwnerType != ownerType;
+
+        Type[] args = original.getActualTypeArguments();
+        for (int t = 0, length = args.length; t < length; t++) {
+          Type resolvedTypeArgument = resolve(context, contextRawType, args[t]);
+          if (resolvedTypeArgument != args[t]) {
+            if (!changed) {
+              args = args.clone();
+              changed = true;
+            }
+            args[t] = resolvedTypeArgument;
+          }
+        }
+
+        return changed
+            ? newParameterizedTypeWithOwner(newOwnerType, original.getRawType(), args)
+            : original;
+
+      } else if (toResolve instanceof WildcardType) {
+        WildcardType original = (WildcardType) toResolve;
+        Type[] originalLowerBound = original.getLowerBounds();
+        Type[] originalUpperBound = original.getUpperBounds();
+
+        if (originalLowerBound.length == 1) {
+          Type lowerBound = resolve(context, contextRawType, originalLowerBound[0]);
+          if (lowerBound != originalLowerBound[0]) {
+            return supertypeOf(lowerBound);
+          }
+        } else if (originalUpperBound.length == 1) {
+          Type upperBound = resolve(context, contextRawType, originalUpperBound[0]);
+          if (upperBound != originalUpperBound[0]) {
+            return subtypeOf(upperBound);
+          }
+        }
+        return original;
+
+      } else {
+        return toResolve;
+      }
+    }
+  }
+
+  static Type resolveTypeVariable(Type context, Class<?> contextRawType, TypeVariable<?> unknown) {
+    Class<?> declaredByRaw = declaringClassOf(unknown);
+
+    // We can't reduce this further.
+    if (declaredByRaw == null) return unknown;
+
+    Type declaredBy = getGenericSupertype(context, contextRawType, declaredByRaw);
+    if (declaredBy instanceof ParameterizedType) {
+      int index = indexOf(declaredByRaw.getTypeParameters(), unknown);
+      return ((ParameterizedType) declaredBy).getActualTypeArguments()[index];
+    }
+
+    return unknown;
+  }
+
+  private static int indexOf(Object[] array, Object toFind) {
+    for (int i = 0; i < array.length; i++) {
+      if (toFind.equals(array[i])) return i;
+    }
+    throw new NoSuchElementException();
+  }
+
+  /**
+   * Returns the declaring class of {@code typeVariable}, or {@code null} if it was not declared by
+   * a class.
+   */
+  private static Class<?> declaringClassOf(TypeVariable<?> typeVariable) {
+    GenericDeclaration genericDeclaration = typeVariable.getGenericDeclaration();
+    return genericDeclaration instanceof Class ? (Class<?>) genericDeclaration : null;
+  }
+
+  private static void checkNotPrimitive(Type type) {
+    if ((type instanceof Class<?>) && ((Class<?>) type).isPrimitive()) {
+      throw new IllegalArgumentException();
+    }
+  }
+
+  private static final class ParameterizedTypeImpl implements ParameterizedType {
+    private final Type ownerType;
+    private final Type rawType;
+    private final Type[] typeArguments;
+
+    public ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
+      // require an owner type if the raw type needs it
+      if (rawType instanceof Class<?>) {
+        Class<?> rawTypeAsClass = (Class<?>) rawType;
+        boolean isStaticOrTopLevelClass = Modifier.isStatic(rawTypeAsClass.getModifiers())
+            || rawTypeAsClass.getEnclosingClass() == null;
+        if (ownerType == null && !isStaticOrTopLevelClass) throw new IllegalArgumentException();
+      }
+
+      this.ownerType = ownerType == null ? null : canonicalize(ownerType);
+      this.rawType = canonicalize(rawType);
+      this.typeArguments = typeArguments.clone();
+      for (int t = 0; t < this.typeArguments.length; t++) {
+        if (this.typeArguments[t] == null) throw new NullPointerException();
+        checkNotPrimitive(this.typeArguments[t]);
+        this.typeArguments[t] = canonicalize(this.typeArguments[t]);
+      }
+    }
+
+    public Type[] getActualTypeArguments() {
+      return typeArguments.clone();
+    }
+
+    public Type getRawType() {
+      return rawType;
+    }
+
+    public Type getOwnerType() {
+      return ownerType;
+    }
+
+    @Override public boolean equals(Object other) {
+      return other instanceof ParameterizedType
+          && Types.equals(this, (ParameterizedType) other);
+    }
+
+    @Override public int hashCode() {
+      return Arrays.hashCode(typeArguments)
+          ^ rawType.hashCode()
+          ^ hashCodeOrZero(ownerType);
+    }
+
+    @Override public String toString() {
+      StringBuilder result = new StringBuilder(30 * (typeArguments.length + 1));
+      result.append(typeToString(rawType));
+
+      if (typeArguments.length == 0) {
+        return result.toString();
+      }
+
+      result.append("<").append(typeToString(typeArguments[0]));
+      for (int i = 1; i < typeArguments.length; i++) {
+        result.append(", ").append(typeToString(typeArguments[i]));
+      }
+      return result.append(">").toString();
+    }
+  }
+
+  private static final class GenericArrayTypeImpl implements GenericArrayType {
+    private final Type componentType;
+
+    public GenericArrayTypeImpl(Type componentType) {
+      this.componentType = canonicalize(componentType);
+    }
+
+    public Type getGenericComponentType() {
+      return componentType;
+    }
+
+    @Override public boolean equals(Object o) {
+      return o instanceof GenericArrayType
+          && Types.equals(this, (GenericArrayType) o);
+    }
+
+    @Override public int hashCode() {
+      return componentType.hashCode();
+    }
+
+    @Override public String toString() {
+      return typeToString(componentType) + "[]";
+    }
+  }
+
+  /**
+   * The WildcardType interface supports multiple upper bounds and multiple lower bounds. We only
+   * support what the Java 6 language needs - at most one bound. If a lower bound is set, the upper
+   * bound must be Object.class.
+   */
+  private static final class WildcardTypeImpl implements WildcardType {
+    private final Type upperBound;
+    private final Type lowerBound;
+
+    public WildcardTypeImpl(Type[] upperBounds, Type[] lowerBounds) {
+      if (lowerBounds.length > 1) throw new IllegalArgumentException();
+      if (upperBounds.length != 1) throw new IllegalArgumentException();
+
+      if (lowerBounds.length == 1) {
+        if (lowerBounds[0] == null) throw new NullPointerException();
+        checkNotPrimitive(lowerBounds[0]);
+        if (upperBounds[0] != Object.class) throw new IllegalArgumentException();
+        this.lowerBound = canonicalize(lowerBounds[0]);
+        this.upperBound = Object.class;
+
+      } else {
+        if (upperBounds[0] == null) throw new NullPointerException();
+        checkNotPrimitive(upperBounds[0]);
+        this.lowerBound = null;
+        this.upperBound = canonicalize(upperBounds[0]);
+      }
+    }
+
+    public Type[] getUpperBounds() {
+      return new Type[] { upperBound };
+    }
+
+    public Type[] getLowerBounds() {
+      return lowerBound != null ? new Type[] { lowerBound } : EMPTY_TYPE_ARRAY;
+    }
+
+    @Override public boolean equals(Object other) {
+      return other instanceof WildcardType
+          && Types.equals(this, (WildcardType) other);
+    }
+
+    @Override public int hashCode() {
+      // This equals Arrays.hashCode(getLowerBounds()) ^ Arrays.hashCode(getUpperBounds()).
+      return (lowerBound != null ? 31 + lowerBound.hashCode() : 1)
+          ^ (31 + upperBound.hashCode());
+    }
+
+    @Override public String toString() {
+      if (lowerBound != null) {
+        return "? super " + typeToString(lowerBound);
+      } else if (upperBound == Object.class) {
+        return "?";
+      } else {
+        return "? extends " + typeToString(upperBound);
+      }
+    }
+  }
+}

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

@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2010 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.moshi;
+
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertNull;
+
+public class TypesTest {
+  @Test public void newParameterizedTypeWithoutOwner() throws Exception {
+    // List<A>. List is a top-level class.
+    Type type = Types.newParameterizedTypeWithOwner(null, List.class, A.class);
+    assertThat(getFirstTypeArgument(type)).isEqualTo(A.class);
+
+    // A<B>. A is a static inner class.
+    type = Types.newParameterizedTypeWithOwner(null, A.class, B.class);
+    assertThat(getFirstTypeArgument(type)).isEqualTo(B.class);
+
+    final class D {
+    }
+    try {
+      // D<A> is not allowed since D is not a static inner class.
+      Types.newParameterizedTypeWithOwner(null, D.class, A.class);
+    } catch (IllegalArgumentException expected) {
+    }
+
+    // A<D> is allowed.
+    type = Types.newParameterizedTypeWithOwner(null, A.class, D.class);
+    assertThat(getFirstTypeArgument(type)).isEqualTo(D.class);
+  }
+
+  @Test public void getFirstTypeArgument() throws Exception {
+    assertNull(getFirstTypeArgument(A.class));
+
+    Type type = Types.newParameterizedTypeWithOwner(null, A.class, B.class, C.class);
+    assertThat(getFirstTypeArgument(type)).isEqualTo(B.class);
+  }
+
+  private static final class A {
+  }
+
+  private static final class B {
+  }
+
+  private static final class C {
+  }
+
+  /**
+   * Given a parameterized type {@code A<B, C>}, returns B. If the specified type is not a generic
+   * type, returns null.
+   */
+  public static Type getFirstTypeArgument(Type type) throws Exception {
+    if (!(type instanceof ParameterizedType)) return null;
+    ParameterizedType ptype = (ParameterizedType) type;
+    Type[] actualTypeArguments = ptype.getActualTypeArguments();
+    if (actualTypeArguments.length == 0) return null;
+    return Types.canonicalize(actualTypeArguments[0]);
+  }
+
+  Map<String, Integer> mapOfStringInteger;
+  Map<String, Integer>[] arrayOfMapOfStringInteger;
+  ArrayList<Map<String, Integer>> arrayListOfMapOfStringInteger;
+  interface StringIntegerMap extends Map<String, Integer> {
+  }
+
+  @Test public void typeLiteral() throws Exception {
+    TypeLiteral<Map<String, Integer>> typeLiteral = new TypeLiteral<Map<String, Integer>>() {};
+    TypeLiteral<?> fromReflection = TypeLiteral.get(
+        TypesTest.class.getDeclaredField("mapOfStringInteger").getGenericType());
+    assertThat(typeLiteral).isEqualTo(fromReflection);
+    assertThat(typeLiteral.hashCode()).isEqualTo(fromReflection.hashCode());
+    assertThat(typeLiteral.toString())
+        .isEqualTo("java.util.Map<java.lang.String, java.lang.Integer>");
+    assertThat(typeLiteral.getRawType()).isEqualTo(Map.class);
+  }
+
+  @Test public void arrayComponentType() throws Exception {
+    assertThat(Types.arrayComponentType(String[][].class)).isEqualTo(String[].class);
+    assertThat(Types.arrayComponentType(String[].class)).isEqualTo(String.class);
+
+    Type arrayOfMapOfStringIntegerType = TypesTest.class.getDeclaredField(
+        "arrayOfMapOfStringInteger").getGenericType();
+    Type mapOfStringIntegerType = TypesTest.class.getDeclaredField(
+        "mapOfStringInteger").getGenericType();
+    assertThat(Types.arrayComponentType(arrayOfMapOfStringIntegerType))
+        .isEqualTo(mapOfStringIntegerType);
+  }
+
+  @Test public void collectionElementType() throws Exception {
+    Type arrayListOfMapOfStringIntegerType = TypesTest.class.getDeclaredField(
+        "arrayListOfMapOfStringInteger").getGenericType();
+    Type mapOfStringIntegerType = TypesTest.class.getDeclaredField(
+        "mapOfStringInteger").getGenericType();
+    assertThat(Types.collectionElementType(arrayListOfMapOfStringIntegerType, List.class))
+        .isEqualTo(mapOfStringIntegerType);
+  }
+
+  @Test public void mapKeyAndValueTypes() throws Exception {
+    Type mapOfStringIntegerType = TypesTest.class.getDeclaredField(
+        "mapOfStringInteger").getGenericType();
+    assertThat(Types.mapKeyAndValueTypes(mapOfStringIntegerType, Map.class))
+        .containsExactly(String.class, Integer.class);
+  }
+
+  @Test public void propertiesTypes() throws Exception {
+    assertThat(Types.mapKeyAndValueTypes(Properties.class, Properties.class))
+        .containsExactly(String.class, String.class);
+  }
+
+  @Test public void fixedVariablesTypes() throws Exception {
+    assertThat(Types.mapKeyAndValueTypes(StringIntegerMap.class, StringIntegerMap.class))
+        .containsExactly(String.class, Integer.class);
+  }
+}