wrong realEntry when some export

[lefreet]

Version

4.0.0

Reproduction link

https://github.com/vuejs/vue-cli

Environment info

osx 10.13
chrome v76

Steps to reproduce

when i try to build a umd module vue-cli-service build --target lib --name test --dest public/test src/views/test/index.js --formats umd

// index.js
export { default } from './test.vue'

i see here

/\b(export\s default|export\s{[^}] as\s default)\b/

and get a empty module，it have a more complete validator？

and then i try

export { default } from './test.vue'
// import Test from './test.vue'
// export default Test

it run fine, haha

What is expected?

get module normal

What is actually happening?

get a empty Symbol

[vue-bot]

Hello!
This issue has gone quiet. Spooky quiet. 👻

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