fix(es2018): add a target and an initial lib

Fixes #20342

Gulpfile.ts

@@ -145,6 +145,10 @@ const es2017LibrarySource = [
 const es2017LibrarySourceMap = es2017LibrarySource.map(source =>
     ({ target: "lib." + source, sources: ["header.d.ts", source] }));
 
+const es2018LibrarySource = [];
+const es2018LibrarySourceMap = es2018LibrarySource.map(source =>
+    ({ target: "lib." + source, sources: ["header.d.ts", source] }));
+
 const esnextLibrarySource = [
     "esnext.asynciterable.d.ts"
 ];
@@ -166,15 +170,17 @@ const librarySourceMap = [
     { target: "lib.es2015.d.ts", sources: ["header.d.ts", "es2015.d.ts"] },
     { target: "lib.es2016.d.ts", sources: ["header.d.ts", "es2016.d.ts"] },
     { target: "lib.es2017.d.ts", sources: ["header.d.ts", "es2017.d.ts"] },
+    { target: "lib.es2018.d.ts", sources: ["header.d.ts", "es2018.d.ts"] },
     { target: "lib.esnext.d.ts", sources: ["header.d.ts", "esnext.d.ts"] },
 
     // JavaScript + all host library
     { target: "lib.d.ts", sources: ["header.d.ts", "es5.d.ts"].concat(hostsLibrarySources) },
     { target: "lib.es6.d.ts", sources: ["header.d.ts", "es5.d.ts"].concat(es2015LibrarySources, hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.es2016.full.d.ts", sources: ["header.d.ts", "es2016.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.es2017.full.d.ts", sources: ["header.d.ts", "es2017.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
+    { target: "lib.es2018.full.d.ts", sources: ["header.d.ts", "es2018.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.esnext.full.d.ts", sources: ["header.d.ts", "esnext.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
-].concat(es2015LibrarySourceMap, es2016LibrarySourceMap, es2017LibrarySourceMap, esnextLibrarySourceMap);
+].concat(es2015LibrarySourceMap, es2016LibrarySourceMap, es2017LibrarySourceMap, es2018LibrarySourceMap, esnextLibrarySourceMap);
 
 const libraryTargets = librarySourceMap.map(f =>
     path.join(builtLocalDirectory, f.target));

Jakefile.js

@@ -205,6 +205,12 @@ var es2017LibrarySourceMap = es2017LibrarySource.map(function (source) {
     return { target: "lib." + source, sources: ["header.d.ts", source] };
 });
 
+var es2018LibrarySource = [];
+
+var es2018LibrarySourceMap = es2018LibrarySource.map(function (source) {
+    return { target: "lib." + source, sources: ["header.d.ts", source] };
+});
+
 var esnextLibrarySource = [
     "esnext.asynciterable.d.ts"
 ];
@@ -227,15 +233,17 @@ var librarySourceMap = [
     { target: "lib.es2015.d.ts", sources: ["header.d.ts", "es2015.d.ts"] },
     { target: "lib.es2016.d.ts", sources: ["header.d.ts", "es2016.d.ts"] },
     { target: "lib.es2017.d.ts", sources: ["header.d.ts", "es2017.d.ts"] },
+    { target: "lib.es2018.d.ts", sources: ["header.d.ts", "es2018.d.ts"] },
     { target: "lib.esnext.d.ts", sources: ["header.d.ts", "esnext.d.ts"] },
 
     // JavaScript + all host library
     { target: "lib.d.ts", sources: ["header.d.ts", "es5.d.ts"].concat(hostsLibrarySources) },
     { target: "lib.es6.d.ts", sources: ["header.d.ts", "es5.d.ts"].concat(es2015LibrarySources, hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.es2016.full.d.ts", sources: ["header.d.ts", "es2016.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.es2017.full.d.ts", sources: ["header.d.ts", "es2017.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
+    { target: "lib.es2018.full.d.ts", sources: ["header.d.ts", "es2018.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
     { target: "lib.esnext.full.d.ts", sources: ["header.d.ts", "esnext.d.ts"].concat(hostsLibrarySources, "dom.iterable.d.ts") },
-].concat(es2015LibrarySourceMap, es2016LibrarySourceMap, es2017LibrarySourceMap, esnextLibrarySourceMap);
+].concat(es2015LibrarySourceMap, es2016LibrarySourceMap, es2017LibrarySourceMap, es2018LibrarySourceMap, esnextLibrarySourceMap);
 
 var libraryTargets = librarySourceMap.map(function (f) {
     return path.join(builtLocalDirectory, f.target);

lib/lib.es2018.d.ts

@@ -0,0 +1,21 @@
+/*! *****************************************************************************
+Copyright (c) Microsoft Corporation. All rights reserved. 
+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  
+ 
+THIS CODE IS PROVIDED ON AN *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE, 
+MERCHANTABLITY OR NON-INFRINGEMENT. 
+ 
+See the Apache Version 2.0 License for specific language governing permissions
+and limitations under the License.
+***************************************************************************** */
+
+
+
+/// <reference no-default-lib="true"/>
+
+
+/// <reference path="lib.es2017.d.ts" />