Use ESNext instead of ES2018

src/compiler/commandLineParser.ts

@@ -100,12 +100,12 @@ namespace ts {
                 "umd": ModuleKind.UMD,
                 "es6": ModuleKind.ES2015,
                 "es2015": ModuleKind.ES2015,
-                "es2018": ModuleKind.ES2018
+                "es2018": ModuleKind.ESNext
             }),
             paramType: Diagnostics.KIND,
             showInSimplifiedHelpView: true,
             category: Diagnostics.Basic_Options,
-            description: Diagnostics.Specify_module_code_generation_Colon_commonjs_amd_system_umd_es2015_or_es2018,
+            description: Diagnostics.Specify_module_code_generation_Colon_commonjs_amd_system_umd_es2015_or_ESNext,
         },
         {
             name: "lib",

src/compiler/diagnosticMessages.json

@@ -2646,7 +2646,7 @@
         "category": "Message",
         "code": 6015
     },
-    "Specify module code generation: 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'es2018'.": {
+    "Specify module code generation: 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'.": {
         "category": "Message",
         "code": 6016
     },

src/compiler/transformer.ts

@@ -15,7 +15,7 @@
 namespace ts {
     function getModuleTransformer(moduleKind: ModuleKind): TransformerFactory<SourceFile> {
         switch (moduleKind) {
-            case ModuleKind.ES2018:
+            case ModuleKind.ESNext:
             case ModuleKind.ES2015:
                 return transformES2015Module;
             case ModuleKind.System:

src/compiler/types.ts

@@ -3579,7 +3579,7 @@ namespace ts {
         UMD = 3,
         System = 4,
         ES2015 = 5,
-        ES2018 = 6
+        ESNext = 6
     }
 
     export const enum JsxEmit {