mixins don't work when using ESNext in tsconfig to compile

[widcraft]

Description

There was no problem when I use commonJS to bundle my lit project. However, when I use ESNext, the bundling process is ok, but my page won't stop loading. I found out what causes the loading problem..... when I change props in mixin it causes the problem. Am I wrong to use mixin like this?

• tsconfig.json

"target": "ES5"
"module": "ESNext"
"sourceMap": true
"outDir": "./dist" 
"rootDir": "./src"
"strict": true
"moduleResolution": "node"
"esModuleInterop": true
"experimentalDecorators": true
"skipLibCheck": true
"forceConsistentCasingInFileNames": true

• mixin

  export const PendingContainer = <TBase extends AnyConstructor<LitElement>>(Base: TBase) => {
  class Mixin extends Base {
  @property({ type: Boolean }) hasPendingChildren = false
  
  constructor(...args: any[]) {
    super()
    let pendingCount = 0
    this.addEventListener('pending-state', async (e: Event) => {
      e.preventDefault()
      const detail = e as MutableObject
      pendingCount++
      this.hasPendingChildren = true
      await detail.promise
      pendingCount--
      this.hasPendingChildren = pendingCount != 0 // this line caused the problem. when i delete this it works find
    })
  }
  }
  return Mixin
  }

Acceptance criteria

What the card must do in order to accept it as complete. Acceptance Criteria must be concrete or measurable.

[sorvell]

Closing due to age. If you're still having a problem with this, please post a reproduction using the lit.dev/playground. Thanks.