Valid TypeScript has "SyntaxError: '=' expected."

The following code causes a SyntaxError, despite being syntactically/stylistically correct:

const bar = (...varargs:any[]) => {
  console.log(varargs);
};

const foo = (x:string):void => (
  bar(
    x,
    () => {},
    () => {}
  )
);

Here is the result:

SyntaxError: '=' expected. (6:6)
  4 | 
  5 | const foo = (x:string):void => (
> 6 |   bar(
    |      ^
  7 |     x,
  8 |     () => {},
  9 |     () => {}

Here is a link to the issue reproduced in the prettier playground. Note that if the parser is changed to babylon then there is no error shown.

Thanks for any assistance!

EDIT: I’m using prettier@1.6.1 and typescript@2.2.2.

[JamesHenry]

Funky, seems to be an issue with the TypeScript 2.5 RC. This parses fine in stable TypeScript 2.4, but not in 2.5.1.

I’ll report it to the TS team

[azz]

This is not fixed in lastest (2.5.2) but is fixed in insiders (2.5.3-insiders.20170909)