From 23f4b990375efcac2c144592cf4ca558722dcf2d Mon Sep 17 00:00:00 2001
From: dcodeIO <dcode@dcode.io>
Date: Thu, 20 Apr 2017 14:42:45 +0200
Subject: [PATCH] Docs: Replaced nullable types with explicit type|null for
 better tooling compatibility, also fixes #766 and fixes 767

---
 cli/targets/static.js |  4 ++--
 index.d.ts            | 56 +++++++++++++++++++++----------------------
 src/common.js         |  2 +-
 src/enum.js           |  2 +-
 src/field.js          | 12 +++++-----
 src/index-light.js    |  2 +-
 src/mapfield.js       |  2 +-
 src/message.js        |  2 +-
 src/method.js         |  4 ++--
 src/namespace.js      |  8 +++----
 src/object.js         |  6 ++---
 src/root.js           |  2 +-
 src/rpc.js            |  4 ++--
 src/rpc/service.js    |  6 ++---
 src/service.js        |  2 +-
 src/tokenize.js       | 12 +++++-----
 src/type.js           |  8 +++----
 src/util/minimal.js   | 17 ++-----------
 src/writer.js         |  5 ++--
 19 files changed, 71 insertions(+), 85 deletions(-)

diff --git a/cli/targets/static.js b/cli/targets/static.js
index cc2a450a8..86178b02e 100644
--- a/cli/targets/static.js
+++ b/cli/targets/static.js
@@ -514,7 +514,7 @@ function buildType(ref, type) {
         pushComment([
             "Verifies " + aOrAn(type.name) + " message.",
             "@param {Object.<string,*>} " + (config.beautify ? "message" : "m") + " Plain object to verify",
-            "@returns {?string} `null` if valid, otherwise the reason why it is not"
+            "@returns {string|null} `null` if valid, otherwise the reason why it is not"
         ]);
         buildFunction(type, "verify", protobuf.verifier(type));
     }
@@ -597,7 +597,7 @@ function buildService(ref, service) {
             // This is a more specialized version of protobuf.rpc.ServiceCallback
             "@typedef " + cbName,
             "@type {function}",
-            "@param {?Error} error Error, if any",
+            "@param {Error|null} error Error, if any",
             "@param {" + method.resolvedResponseType.fullName.substring(1) + "} [response] " + method.resolvedResponseType.name
         ]);
         push("");
diff --git a/index.d.ts b/index.d.ts
index 45682a5aa..a6add4ac5 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -24,7 +24,7 @@ export namespace common {
      * @param file Proto file name
      * @returns Root definition or `null` if not defined
      */
-    function get(file: string): INamespace;
+    function get(file: string): (INamespace|null);
 
     /** Properties of a google.protobuf.Any message. */
     interface IAny {
@@ -186,12 +186,12 @@ export class Enum extends ReflectionObject {
      * Adds a value to this enum.
      * @param name Value name
      * @param id Value id
-     * @param comment Comment, if any
+     * @param [comment] Comment, if any
      * @returns `this`
      * @throws {TypeError} If arguments are invalid
      * @throws {Error} If there is already a value with this name or id
      */
-    public add(name: string, id: number, comment: string): Enum;
+    public add(name: string, id: number, comment?: string): Enum;
 
     /**
      * Removes a value from this enum
@@ -298,10 +298,10 @@ export class FieldBase extends ReflectionObject {
     public map: boolean;
 
     /** Message this field belongs to. */
-    public message: Type;
+    public message: (Type|null);
 
     /** OneOf this field belongs to, if any, */
-    public partOf: OneOf;
+    public partOf: (OneOf|null);
 
     /** The field type's default value. */
     public typeDefault: any;
@@ -316,13 +316,13 @@ export class FieldBase extends ReflectionObject {
     public bytes: boolean;
 
     /** Resolved type if not a basic type. */
-    public resolvedType: (Type|Enum);
+    public resolvedType: (Type|Enum|null);
 
     /** Sister-field within the extended type if a declaring extension field. */
-    public extensionField: Field;
+    public extensionField: (Field|null);
 
     /** Sister-field within the declaring namespace if an extended field. */
-    public declaringField: Field;
+    public declaringField: (Field|null);
 
     /**
      * Converts this field to a field descriptor.
@@ -373,7 +373,7 @@ type FieldDecorator = (prototype: object, fieldName: string) => void;
  * @param error Error, if any, otherwise `null`
  * @param [root] Root, if there hasn't been an error
  */
-type LoadCallback = (error: Error, root?: Root) => void;
+type LoadCallback = (error: (Error|null), root?: Root) => void;
 
 /**
  * Loads one or multiple .proto or preprocessed .json files into a common root namespace and calls the callback.
@@ -434,7 +434,7 @@ export class MapField extends FieldBase {
     public keyType: string;
 
     /** Resolved key type if not a basic type. */
-    public resolvedKeyType: ReflectionObject;
+    public resolvedKeyType: (ReflectionObject|null);
 
     /**
      * Constructs a map field from a map field descriptor.
@@ -532,7 +532,7 @@ export class Message<T extends object> {
      * @param message Plain object to verify
      * @returns `null` if valid, otherwise the reason why it is not
      */
-    public static verify(message: { [k: string]: any }): string;
+    public static verify(message: { [k: string]: any }): (string|null);
 
     /**
      * Creates a new message of this type from a plain object. Also converts values to their respective internal types.
@@ -587,10 +587,10 @@ export class Method extends ReflectionObject {
     public responseStream?: boolean;
 
     /** Resolved request type. */
-    public resolvedRequestType: Type;
+    public resolvedRequestType: (Type|null);
 
     /** Resolved response type. */
-    public resolvedResponseType: Type;
+    public resolvedResponseType: (Type|null);
 
     /**
      * Constructs a method from a method descriptor.
@@ -684,7 +684,7 @@ export abstract class NamespaceBase extends ReflectionObject {
      * @param name Nested object name
      * @returns The reflection object or `null` if it doesn't exist
      */
-    public get(name: string): ReflectionObject;
+    public get(name: string): (ReflectionObject|null);
 
     /**
      * Gets the values of the nested {@link Enum|enum} of the specified name.
@@ -734,7 +734,7 @@ export abstract class NamespaceBase extends ReflectionObject {
      * @param [parentAlreadyChecked=false] If known, whether the parent has already been checked
      * @returns Looked up object or `null` if none could be found
      */
-    public lookup(path: (string|string[]), filterTypes: (any|any[]), parentAlreadyChecked?: boolean): ReflectionObject;
+    public lookup(path: (string|string[]), filterTypes: (any|any[]), parentAlreadyChecked?: boolean): (ReflectionObject|null);
 
     /**
      * Looks up the reflection object at the specified path, relative to this namespace.
@@ -742,7 +742,7 @@ export abstract class NamespaceBase extends ReflectionObject {
      * @param [parentAlreadyChecked=false] Whether the parent has already been checked
      * @returns Looked up object or `null` if none could be found
      */
-    public lookup(path: (string|string[]), parentAlreadyChecked?: boolean): ReflectionObject;
+    public lookup(path: (string|string[]), parentAlreadyChecked?: boolean): (ReflectionObject|null);
 
     /**
      * Looks up the {@link Type|type} at the specified path, relative to this namespace.
@@ -807,16 +807,16 @@ export abstract class ReflectionObject {
     public name: string;
 
     /** Parent namespace. */
-    public parent: Namespace;
+    public parent: (Namespace|null);
 
     /** Whether already resolved or not. */
     public resolved: boolean;
 
     /** Comment text, if any. */
-    public comment: string;
+    public comment: (string|null);
 
     /** Defining file name. */
-    public filename: string;
+    public filename: (string|null);
 
     /** Reference to the root namespace. */
     public readonly root: Root;
@@ -1173,7 +1173,7 @@ export class Root extends NamespaceBase {
      * @param target The file name being imported
      * @returns Resolved path to `target` or `null` to skip the file
      */
-    public resolvePath(origin: string, target: string): string;
+    public resolvePath(origin: string, target: string): (string|null);
 
     /**
      * Loads one or multiple .proto or preprocessed .json files into this root namespace and calls the callback.
@@ -1218,7 +1218,7 @@ export namespace rpc {
      * @param error Error, if any
      * @param [response] Response message
      */
-    type ServiceMethodCallback<TRes extends Message<TRes>> = (error: Error, response?: TRes) => void;
+    type ServiceMethodCallback<TRes extends Message<TRes>> = (error: (Error|null), response?: TRes) => void;
 
     /**
      * A service method part of a {@link rpc.Service} as created by {@link Service.create}.
@@ -1240,7 +1240,7 @@ export namespace rpc {
         constructor(rpcImpl: RPCImpl, requestDelimited?: boolean, responseDelimited?: boolean);
 
         /** RPC implementation. Becomes `null` once the service is ended. */
-        public rpcImpl: RPCImpl;
+        public rpcImpl: (RPCImpl|null);
 
         /** Whether requests are length-delimited. */
         public requestDelimited: boolean;
@@ -1280,7 +1280,7 @@ type RPCImpl = (method: (Method|rpc.ServiceMethod<Message<{}>, Message<{}>>), re
  * @param error Error, if any, otherwise `null`
  * @param [response] Response data or `null` to signal end of stream, if there hasn't been an error
  */
-type RPCImplCallback = (error: Error, response?: Uint8Array) => void;
+type RPCImplCallback = (error: (Error|null), response?: (Uint8Array|null)) => void;
 
 /** Reflected service. */
 export class Service extends NamespaceBase {
@@ -1335,13 +1335,13 @@ export interface IService extends INamespace {
  * Gets the next token and advances.
  * @returns Next token or `null` on eof
  */
-type TokenizerHandleNext = () => string;
+type TokenizerHandleNext = () => (string|null);
 
 /**
  * Peeks for the next token.
  * @returns Next token or `null` on eof
  */
-type TokenizerHandlePeek = () => string;
+type TokenizerHandlePeek = () => (string|null);
 
 /**
  * Pushes a token back to the stack.
@@ -1363,7 +1363,7 @@ type TokenizerHandleSkip = (expected: string, optional?: boolean) => boolean;
  * @param [line] Line number
  * @returns Comment text or `null` if none
  */
-type TokenizerHandleCmnt = (line?: number) => string;
+type TokenizerHandleCmnt = (line?: number) => (string|null);
 
 /** Handle object returned from {@link tokenize}. */
 export interface ITokenizerHandle {
@@ -1547,7 +1547,7 @@ export class Type extends NamespaceBase {
      * @param message Plain object to verify
      * @returns `null` if valid, otherwise the reason why it is not
      */
-    public verify(message: { [k: string]: any }): string;
+    public verify(message: { [k: string]: any }): (null|string);
 
     /**
      * Creates a new message of this type from a plain object. Also converts values to their respective internal types.
@@ -2381,7 +2381,7 @@ export class Writer {
     public tail: object;
 
     /** Linked forked states. */
-    public states: object;
+    public states: (object|null);
 
     /**
      * Creates a new writer.
diff --git a/src/common.js b/src/common.js
index a6f0005dc..03822d82b 100644
--- a/src/common.js
+++ b/src/common.js
@@ -42,7 +42,7 @@ function common(name, json) {
  * @name common.get
  * @function
  * @param {string} file Proto file name
- * @returns {?INamespace} Root definition or `null` if not defined
+ * @returns {INamespace|null} Root definition or `null` if not defined
  */
 common.get = function get(file) {
     return common[file] || null;
diff --git a/src/enum.js b/src/enum.js
index f28fe8741..2ca67aa18 100644
--- a/src/enum.js
+++ b/src/enum.js
@@ -83,7 +83,7 @@ Enum.prototype.toJSON = function toJSON() {
  * Adds a value to this enum.
  * @param {string} name Value name
  * @param {number} id Value id
- * @param {?string} comment Comment, if any
+ * @param {string} [comment] Comment, if any
  * @returns {Enum} `this`
  * @throws {TypeError} If arguments are invalid
  * @throws {Error} If there is already a value with this name or id
diff --git a/src/field.js b/src/field.js
index 9b611f448..c33a34456 100644
--- a/src/field.js
+++ b/src/field.js
@@ -125,13 +125,13 @@ function Field(name, id, type, rule, extend, options) {
 
     /**
      * Message this field belongs to.
-     * @type {?Type}
+     * @type {Type|null}
      */
     this.message = null;
 
     /**
      * OneOf this field belongs to, if any,
-     * @type {?OneOf}
+     * @type {OneOf|null}
      */
     this.partOf = null;
 
@@ -161,25 +161,25 @@ function Field(name, id, type, rule, extend, options) {
 
     /**
      * Resolved type if not a basic type.
-     * @type {?(Type|Enum)}
+     * @type {Type|Enum|null}
      */
     this.resolvedType = null;
 
     /**
      * Sister-field within the extended type if a declaring extension field.
-     * @type {?Field}
+     * @type {Field|null}
      */
     this.extensionField = null;
 
     /**
      * Sister-field within the declaring namespace if an extended field.
-     * @type {?Field}
+     * @type {Field|null}
      */
     this.declaringField = null;
 
     /**
      * Internally remembers whether this field is packed.
-     * @type {?boolean}
+     * @type {boolean|null}
      * @private
      */
     this._packed = null;
diff --git a/src/index-light.js b/src/index-light.js
index 35ad3c566..5d4dc1f14 100644
--- a/src/index-light.js
+++ b/src/index-light.js
@@ -7,7 +7,7 @@ protobuf.build = "light";
  * A node-style callback as used by {@link load} and {@link Root#load}.
  * @typedef LoadCallback
  * @type {function}
- * @param {?Error} error Error, if any, otherwise `null`
+ * @param {Error|null} error Error, if any, otherwise `null`
  * @param {Root} [root] Root, if there hasn't been an error
  * @returns {undefined}
  */
diff --git a/src/mapfield.js b/src/mapfield.js
index 58c4ca32c..7e1714fa3 100644
--- a/src/mapfield.js
+++ b/src/mapfield.js
@@ -34,7 +34,7 @@ function MapField(name, id, keyType, type, options) {
 
     /**
      * Resolved key type if not a basic type.
-     * @type {?ReflectionObject}
+     * @type {ReflectionObject|null}
      */
     this.resolvedKeyType = null;
 
diff --git a/src/message.js b/src/message.js
index 6839a451e..b827496f6 100644
--- a/src/message.js
+++ b/src/message.js
@@ -99,7 +99,7 @@ Message.decodeDelimited = function decodeDelimited(reader) {
  * @name Message.verify
  * @function
  * @param {Object.<string,*>} message Plain object to verify
- * @returns {?string} `null` if valid, otherwise the reason why it is not
+ * @returns {string|null} `null` if valid, otherwise the reason why it is not
  */
 Message.verify = function verify(message) {
     return this.$type.verify(message);
diff --git a/src/method.js b/src/method.js
index 074adf3f9..dac99b260 100644
--- a/src/method.js
+++ b/src/method.js
@@ -77,13 +77,13 @@ function Method(name, type, requestType, responseType, requestStream, responseSt
 
     /**
      * Resolved request type.
-     * @type {?Type}
+     * @type {Type|null}
      */
     this.resolvedRequestType = null;
 
     /**
      * Resolved response type.
-     * @type {?Type}
+     * @type {Type|null}
      */
     this.resolvedResponseType = null;
 }
diff --git a/src/namespace.js b/src/namespace.js
index 2d5e01f2e..7d6bd6d1c 100644
--- a/src/namespace.js
+++ b/src/namespace.js
@@ -74,7 +74,7 @@ function Namespace(name, options) {
 
     /**
      * Cached nested objects as an array.
-     * @type {?ReflectionObject[]}
+     * @type {ReflectionObject[]|null}
      * @private
      */
     this._nestedArray = null;
@@ -158,7 +158,7 @@ Namespace.prototype.addJSON = function addJSON(nestedJson) {
 /**
  * Gets the nested object of the specified name.
  * @param {string} name Nested object name
- * @returns {?ReflectionObject} The reflection object or `null` if it doesn't exist
+ * @returns {ReflectionObject|null} The reflection object or `null` if it doesn't exist
  */
 Namespace.prototype.get = function get(name) {
     return this.nested && this.nested[name]
@@ -285,7 +285,7 @@ Namespace.prototype.resolveAll = function resolveAll() {
  * @param {string|string[]} path Path to look up
  * @param {*|Array.<*>} filterTypes Filter types, any combination of the constructors of `protobuf.Type`, `protobuf.Enum`, `protobuf.Service` etc.
  * @param {boolean} [parentAlreadyChecked=false] If known, whether the parent has already been checked
- * @returns {?ReflectionObject} Looked up object or `null` if none could be found
+ * @returns {ReflectionObject|null} Looked up object or `null` if none could be found
  */
 Namespace.prototype.lookup = function lookup(path, filterTypes, parentAlreadyChecked) {
 
@@ -334,7 +334,7 @@ Namespace.prototype.lookup = function lookup(path, filterTypes, parentAlreadyChe
  * @function
  * @param {string|string[]} path Path to look up
  * @param {boolean} [parentAlreadyChecked=false] Whether the parent has already been checked
- * @returns {?ReflectionObject} Looked up object or `null` if none could be found
+ * @returns {ReflectionObject|null} Looked up object or `null` if none could be found
  * @variation 2
  */
 // lookup(path: string, [parentAlreadyChecked: boolean])
diff --git a/src/object.js b/src/object.js
index d36d4b525..28da69236 100644
--- a/src/object.js
+++ b/src/object.js
@@ -37,7 +37,7 @@ function ReflectionObject(name, options) {
 
     /**
      * Parent namespace.
-     * @type {?Namespace}
+     * @type {Namespace|null}
      */
     this.parent = null;
 
@@ -49,13 +49,13 @@ function ReflectionObject(name, options) {
 
     /**
      * Comment text, if any.
-     * @type {?string}
+     * @type {string|null}
      */
     this.comment = null;
 
     /**
      * Defining file name.
-     * @type {?string}
+     * @type {string|null}
      */
     this.filename = null;
 }
diff --git a/src/root.js b/src/root.js
index 43cfd43d3..3dab68743 100644
--- a/src/root.js
+++ b/src/root.js
@@ -57,7 +57,7 @@ Root.fromJSON = function fromJSON(json, root) {
  * @function
  * @param {string} origin The file name of the importing file
  * @param {string} target The file name being imported
- * @returns {?string} Resolved path to `target` or `null` to skip the file
+ * @returns {string|null} Resolved path to `target` or `null` to skip the file
  */
 Root.prototype.resolvePath = util.path.resolve;
 
diff --git a/src/rpc.js b/src/rpc.js
index f52c7ccab..894e5c7c9 100644
--- a/src/rpc.js
+++ b/src/rpc.js
@@ -28,8 +28,8 @@ var rpc = exports;
  * Node-style callback as used by {@link RPCImpl}.
  * @typedef RPCImplCallback
  * @type {function}
- * @param {?Error} error Error, if any, otherwise `null`
- * @param {?Uint8Array} [response] Response data or `null` to signal end of stream, if there hasn't been an error
+ * @param {Error|null} error Error, if any, otherwise `null`
+ * @param {Uint8Array|null} [response] Response data or `null` to signal end of stream, if there hasn't been an error
  * @returns {undefined}
  */
 
diff --git a/src/rpc/service.js b/src/rpc/service.js
index eb157a8f0..757f382eb 100644
--- a/src/rpc/service.js
+++ b/src/rpc/service.js
@@ -13,8 +13,8 @@ var util = require("../util/minimal");
  * @typedef rpc.ServiceMethodCallback
  * @template TRes extends Message<TRes>
  * @type {function}
- * @param {?Error} error Error, if any
- * @param {?TRes} [response] Response message
+ * @param {Error|null} error Error, if any
+ * @param {TRes} [response] Response message
  * @returns {undefined}
  */
 
@@ -48,7 +48,7 @@ function Service(rpcImpl, requestDelimited, responseDelimited) {
 
     /**
      * RPC implementation. Becomes `null` once the service is ended.
-     * @type {?RPCImpl}
+     * @type {RPCImpl|null}
      */
     this.rpcImpl = rpcImpl;
 
diff --git a/src/service.js b/src/service.js
index 33ee45182..3af0b6b65 100644
--- a/src/service.js
+++ b/src/service.js
@@ -29,7 +29,7 @@ function Service(name, options) {
 
     /**
      * Cached methods as an array.
-     * @type {?Method[]}
+     * @type {Method[]|null}
      * @private
      */
     this._methodsArray = null;
diff --git a/src/tokenize.js b/src/tokenize.js
index bc0b3b4fc..825a7af4f 100644
--- a/src/tokenize.js
+++ b/src/tokenize.js
@@ -42,14 +42,14 @@ tokenize.unescape = unescape;
  * Gets the next token and advances.
  * @typedef TokenizerHandleNext
  * @type {function}
- * @returns {?string} Next token or `null` on eof
+ * @returns {string|null} Next token or `null` on eof
  */
 
 /**
  * Peeks for the next token.
  * @typedef TokenizerHandlePeek
  * @type {function}
- * @returns {?string} Next token or `null` on eof
+ * @returns {string|null} Next token or `null` on eof
  */
 
 /**
@@ -75,7 +75,7 @@ tokenize.unescape = unescape;
  * @typedef TokenizerHandleCmnt
  * @type {function}
  * @param {number} [line] Line number
- * @returns {?string} Comment text or `null` if none
+ * @returns {string|null} Comment text or `null` if none
  */
 
 /**
@@ -179,7 +179,7 @@ function tokenize(source) {
 
     /**
      * Obtains the next token.
-     * @returns {?string} Next token or `null` on eof
+     * @returns {string|null} Next token or `null` on eof
      * @inner
      */
     function next() {
@@ -260,7 +260,7 @@ function tokenize(source) {
 
     /**
      * Peeks for the next token.
-     * @returns {?string} Token or `null` on eof
+     * @returns {string|null} Token or `null` on eof
      * @inner
      */
     function peek() {
@@ -296,7 +296,7 @@ function tokenize(source) {
     /**
      * Gets a comment.
      * @param {number} [trailingLine] Line number if looking for a trailing comment
-     * @returns {?string} Comment text
+     * @returns {string|null} Comment text
      * @inner
      */
     function cmnt(trailingLine) {
diff --git a/src/type.js b/src/type.js
index 170f3e487..90fc83cfa 100644
--- a/src/type.js
+++ b/src/type.js
@@ -63,21 +63,21 @@ function Type(name, options) {
 
     /**
      * Cached fields by id.
-     * @type {?Object.<number,Field>}
+     * @type {Object.<number,Field>|null}
      * @private
      */
     this._fieldsById = null;
 
     /**
      * Cached fields as an array.
-     * @type {?Field[]}
+     * @type {Field[]|null}
      * @private
      */
     this._fieldsArray = null;
 
     /**
      * Cached oneofs as an array.
-     * @type {?OneOf[]}
+     * @type {OneOf[]|null}
      * @private
      */
     this._oneofsArray = null;
@@ -526,7 +526,7 @@ Type.prototype.decodeDelimited = function decodeDelimited(reader) {
 /**
  * Verifies that field values are valid and that required fields are present.
  * @param {Object.<string,*>} message Plain object to verify
- * @returns {?string} `null` if valid, otherwise the reason why it is not
+ * @returns {null|string} `null` if valid, otherwise the reason why it is not
  */
 Type.prototype.verify = function verify_setup(message) {
     return this.setup().verify(message); // overrides this method
diff --git a/src/util/minimal.js b/src/util/minimal.js
index ea4655713..e15a37251 100644
--- a/src/util/minimal.js
+++ b/src/util/minimal.js
@@ -121,23 +121,10 @@ util.Buffer = (function() {
     }
 })();
 
-/**
- * Internal alias of or polyfull for Buffer.from.
- * @type {?function}
- * @param {string|number[]} value Value
- * @param {string} [encoding] Encoding if value is a string
- * @returns {Uint8Array}
- * @private
- */
+// Internal alias of or polyfull for Buffer.from.
 util._Buffer_from = null;
 
-/**
- * Internal alias of or polyfill for Buffer.allocUnsafe.
- * @type {?function}
- * @param {number} size Buffer size
- * @returns {Uint8Array}
- * @private
- */
+// Internal alias of or polyfill for Buffer.allocUnsafe.
 util._Buffer_allocUnsafe = null;
 
 /**
diff --git a/src/writer.js b/src/writer.js
index a046a276c..f77d83c54 100644
--- a/src/writer.js
+++ b/src/writer.js
@@ -54,7 +54,6 @@ function noop() {} // eslint-disable-line no-empty-function
  * @memberof Writer
  * @constructor
  * @param {Writer} writer Writer to copy state from
- * @private
  * @ignore
  */
 function State(writer) {
@@ -79,7 +78,7 @@ function State(writer) {
 
     /**
      * Next state.
-     * @type {?State}
+     * @type {State|null}
      */
     this.next = writer.states;
 }
@@ -111,7 +110,7 @@ function Writer() {
 
     /**
      * Linked forked states.
-     * @type {?Object}
+     * @type {Object|null}
      */
     this.states = null;