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

Beginne mit dem verlinkten TypeScript Playground und vergleiche das fehlschlagende Beispiel export default @x class A {} mit der funktionierenden getrennten Deklaration. Verfolge, wie der Compiler Dekoratoren vor exportierten Klassen verarbeitet, und füge Tests hinzu, die zeigen, dass die erwartete Syntax akzeptiert wird, ohne die bestehende Form zu beeinträchtigen.