[gjs: 11/14] release: Document SpiderMonkey 60 changes

[Philip Chimento <pchimento src gnome org>]

commit 34de292e3f086527904d571d7c814e69c5df951e
Author: Philip Chimento <philip chimento gmail com>
Date:   Sat May 26 20:48:37 2018 -0700

    release: Document SpiderMonkey 60 changes
    
    Includes a change to a comment that previously advocated using a
    nonstandard extension, which is now removed.
    
    See: #161

 NEWS                      | 61 +++++++++++++++++++++++++++++++++++++++++++++++
 modules/overrides/GLib.js |  2 +-
 2 files changed, 62 insertions(+), 1 deletion(-)
---
diff --git a/NEWS b/NEWS
index 759fbdb7..6d79157b 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,67 @@ NEXT
 
 - GJS now depends on SpiderMonkey 60 and requires a compiler capable of C++14.
 
+- New JavaScript features! This version of GJS is based on SpiderMonkey 60, an
+  upgrade from the previous ESR (Extended Support Release) of SpiderMonkey 52.
+  Here are the highlights of the new JavaScript features.
+  For more information, look them up on MDN or devdocs.io.
+
+  * New syntax
+    + `for await (... of ...)` syntax is used for async iteration.
+    + The rest operator is now supported in object destructuring: e.g.
+      `({a, b, ...cd} = {a: 1, b: 2, c: 3, d: 4});`
+    + The spread operator is now supported in object literals: e.g.
+      `mergedObject = {...obj1, ...obj2};`
+    + Generator methods can now be async, using the `async function*` syntax,
+      or `async* f() {...}` method shorthand.
+    + It's now allowed to omit the variable binding from a catch statement, if
+      you don't need to access the thrown exception: `try {...} catch {}`
+
+  * New APIs
+    + Promise.prototype.finally(), popular in many third-party Promise
+      libraries, is now available natively.
+    + String.prototype.toLocaleLowerCase() and
+      String.prototype.toLocaleUpperCase() now take an optional locale or
+      array of locales.
+    + Intl.PluralRules is now available.
+    + Intl.NumberFormat.protoype.formatToParts() is now available.
+    + Intl.Collator now has a caseFirst option.
+    + Intl.DateTimeFormat now has an hourCycle option.
+
+  * New behaviour
+    + There are a lot of minor behaviour changes as SpiderMonkey's JS
+      implementation conforms ever closer to ECMAScript standards. For complete
+      information, read the Firefox developer release notes:
+      https://developer.mozilla.org/en-US/Firefox/Releases/53#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/54#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/55#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/56#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/57#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/58#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/59#JavaScript
+      https://developer.mozilla.org/en-US/Firefox/Releases/60#JavaScript
+
+  * Backwards-incompatible changes
+    + Conditional catch clauses have been removed, as they were a Mozilla
+      extension which will not be standardized. This requires some attention in
+      GJS programs, as previously we condoned code like `catch (e if
+      e.matches(Gio.IOError, Gio.IOError.EXISTS))`  with a comment in
+      overrides/GLib.js, so it's likely this is used in several places.
+    + The nonstandard `for each (... in ...)` loop was removed.
+    + The nonstandard legacy lambda syntax (`function(x) x*x`) was removed.
+    + The nonstandard Mozilla iteration protocol was removed, as well as
+      nonstandard Mozilla generators, including the Iterator and StopIteration
+      objects, and the Function.prototype.isGenerator() method.
+    + Array comprehensions and generator comprehensions have been removed.
+    + Several nonstandard methods were removed: ArrayBuffer.slice() (but not
+      the standard version, ArrayBuffer.prototype.slice()),
+      Date.prototype.toLocaleFormat(), Function.prototype.isGenerator(),
+      Object.prototype.watch(), and Object.prototype.unwatch().
+
+- Many of the above backwards-incompatible changes can be caught by scanning
+  your source code using https://gitlab.gnome.org/ptomato/moz60tool, or
+  https://extensions.gnome.org/extension/1455/spidermonkey-60-migration-validator/
+
 - Deprecation: the custom ByteArray is now discouraged. Instead of ByteArray,
   use Javascript's native Uint8Array. The ByteArray module still contains
   functions for converting between byte arrays, strings, and GLib.Bytes
diff --git a/modules/overrides/GLib.js b/modules/overrides/GLib.js
index fd5ff3b8..9f90d22c 100644
--- a/modules/overrides/GLib.js
+++ b/modules/overrides/GLib.js
@@ -250,7 +250,7 @@ function _init() {
     GLib = this;
 
     // small HACK: we add a matches() method to standard Errors so that
-    // you can do "catch(e if e.matches(Ns.FooError, Ns.FooError.SOME_CODE))"
+    // you can do "if (e.matches(Ns.FooError, Ns.FooError.SOME_CODE))"
     // without checking instanceof
     Error.prototype.matches = function() { return false; };