circular-deps-4

fixed.js

// -- app.js --
import { AbstractNode } from './internal'

/* as is */

// -- internal.js --
export * from './AbstractNode'
export * from './Node'
export * from './Leaf'

// -- AbstractNode.js --
import { Node, Leaf } from './internal'

export class AbstractNode {
   /* as is */
}

// -- Node.js --
import { AbstractNode } from './internal'

export class Node extends AbstractNode {
   /* as is */
}

// -- Leaf.js --
import { AbstractNode } from './internal'

export class Leaf extends AbstractNode {
   /* as is */
}

How come l.12 doesn't result in a circular dependency?