visitWildcardType((WildcardType) type);
        } else if (type instanceof ParameterizedType) {
          visitParameterizedType((ParameterizedType) type);
        } else if (type instanceof Class) {
          visitClass((Class<?>) type);
        } else if (type instanceof GenericArrayType) {
          visitGenericArrayType((GenericArrayType) type);
        } else {
          throw new AssertionError("Unknown type: " + type);
        }

        checkArgument(componentType != null, "%s is not an array type.", to);
        populateTypeMappings(mappings, fromArrayType.getGenericComponentType(), componentType);
      }

      @Override
      void visitClass(Class<?> fromClass) {
        if (to instanceof WildcardType) {
          return; // Okay to say Foo is <?>
        }
        // Can't map from a raw class to anything other than itself or a wildcard.

        checkArgument(componentType != null, "%s is not an array type.", to);
        populateTypeMappings(mappings, fromArrayType.getGenericComponentType(), componentType);
      }

      @Override
      void visitClass(Class<?> fromClass) {
        if (to instanceof WildcardType) {
          return; // Okay to say Foo is <?>
        }
        // Can't map from a raw class to anything other than itself or a wildcard.

      }

      @Override
      void visitGenericArrayType(GenericArrayType t) {
        result.set(t.getGenericComponentType());
      }

      @Override
      void visitClass(Class<?> t) {
        result.set(t.getComponentType());
      }
    }.visit(type);
    return result.get();
  }

  /**

      }

      @Override
      void visitGenericArrayType(GenericArrayType t) {
        result.set(t.getGenericComponentType());
      }

      @Override
      void visitClass(Class<?> t) {
        result.set(t.getComponentType());
      }
    }.visit(type);
    return result.get();
  }

  /**