fix: Derive espree.Syntax from espree.VisitorKeys (#532)

* Fix: Derive espree/Syntax from espree/VisitorKeys

Fixes #531

* Chore: Delete obsolete lib/ast-node-types.js module

espree.js

@@ -58,7 +58,6 @@
 
 import * as acorn from "acorn";
 import jsx from "acorn-jsx";
-import astNodeTypes from "./lib/ast-node-types.js";
 import espree from "./lib/espree.js";
 import espreeVersion from "./lib/version.js";
 import * as visitorKeys from "eslint-visitor-keys";
@@ -141,8 +140,12 @@ export function parse(code, options) {
 
 export const version = espreeVersion;
 
+/* istanbul ignore next */
+export const VisitorKeys = (function() {
+    return visitorKeys.KEYS;
+}());
 
-// Deep copy.
+// Derive node types from VisitorKeys
 /* istanbul ignore next */
 export const Syntax = (function() {
     let name,
@@ -152,9 +155,9 @@ export const Syntax = (function() {
         types = Object.create(null);
     }
 
-    for (name in astNodeTypes) {
-        if (Object.hasOwnProperty.call(astNodeTypes, name)) {
-            types[name] = astNodeTypes[name];
+    for (name in VisitorKeys) {
+        if (Object.hasOwnProperty.call(VisitorKeys, name)) {
+            types[name] = name;
         }
     }
 
@@ -165,11 +168,6 @@ export const Syntax = (function() {
     return types;
 }());
 
-/* istanbul ignore next */
-export const VisitorKeys = (function() {
-    return visitorKeys.KEYS;
-}());
-
 export const latestEcmaVersion = getLatestEcmaVersion();
 
 export const supportedEcmaVersions = getSupportedEcmaVersions();

tests/lib/syntax.js

@@ -0,0 +1,24 @@
+/**
+ * @fileoverview Test for Syntax.
+ */
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+import assert from "assert";
+import * as espree from "../../espree.js";
+
+
+//------------------------------------------------------------------------------
+// Tests
+//------------------------------------------------------------------------------
+
+describe("Syntax", () => {
+    it("keys of Syntax should match the keys of VisitorKeys", () => {
+        assert.deepStrictEqual(
+            Object.keys(espree.Syntax),
+            Object.keys(espree.VisitorKeys)
+        );
+    });
+});