Lazy-initialize babel-traverse to avoid circular dep. (#3497)

packages/babel-types/src/converters.js

@@ -2,7 +2,6 @@ import isPlainObject from "lodash/lang/isPlainObject";
 import isNumber from "lodash/lang/isNumber";
 import isRegExp from "lodash/lang/isRegExp";
 import isString from "lodash/lang/isString";
-import traverse from "babel-traverse";
 import type { Scope } from "babel-traverse";
 import * as t from "./index";
 
@@ -99,7 +98,14 @@ export function toSequenceExpression(nodes: Array<Object>, scope: Scope): ?Objec
   }
 }
 
+// Can't use import because of cyclic dependency between babel-traverse
+// and this module (babel-types). This require needs to appear after
+// we export the TYPES constant, so we lazy-initialize it before use.
+let traverse;
+
 export function toKeyAlias(node: Object, key: Object = node.key): string {
+  if (!traverse) traverse = require("babel-traverse").default;
+
   let alias;
 
   if (node.kind === "method") {

packages/babel-types/src/index.js

@@ -3,7 +3,6 @@ import compact from "lodash/array/compact";
 import loClone from "lodash/lang/clone";
 import each from "lodash/collection/each";
 import uniq from "lodash/array/uniq";
-import traverse from "babel-traverse";
 
 let t = exports;
 
@@ -400,11 +399,18 @@ function _inheritComments(key, child, parent) {
   }
 }
 
+// Can't use import because of cyclic dependency between babel-traverse
+// and this module (babel-types). This require needs to appear after
+// we export the TYPES constant, so we lazy-initialize it before use.
+let traverse;
+
 /**
  * Inherit all contextual properties from `parent` node to `child` node.
  */
 
 export function inherits(child: Object, parent: Object): Object {
+  if (!traverse) traverse = require("babel-traverse").default;
+
   if (!child || !parent) return child;
 
   // optionally inherit specific properties if not null