Experimental Decorators don't work in `export` statements

TypeScript Version: JavaScript + ESNext

Search Terms: export+experimental+decorators+export

Code

export default
@x
class A {
}

[❌ ] The above does not work.

@x
class A {}

export default A;

[👌 ] It does work when going with the old syntax, that is splitting export statement and class expression. I.e. this works fine:

Expected behavior:

The syntax should be valid, according to @babel/plugin-proposal-decorators, which is also in line with tc39, as discussed here.

Actual behavior:

The first @ raises:

Expression expected. ts(1109)

Playground Link:

https://www.typescriptlang.org/play/?target=99&ts=4.0.0-dev.20200714&useJavaScript=true#code/KYDwDg9gTgLgBAE2AMwIYFcA2MBQABGVAcwAoByYAYwFsBaUMTVASwDtgoyBKfGYaxqj7kAPAmYA3AHwiA9OOncclJgGdVcALIBPAMIQBcUH1YINAZUzNqcAN44AvkA

Related Issues:

I previously posted on VSCode issues and was sent here:

• https://github.com/microsoft/vscode/issues/102386

从链接的 TypeScript Playground 开始，将失败的示例 export default @x class A {} 与正常工作的拆分声明进行比较。跟踪编译器如何处理导出类之前的装饰器，然后添加覆盖测试，展示预期语法会被接受，同时不会使现有形式出现回归。