Binary operator after TypeScript as assertion causes wrong SyntaxError

[woongsikchoi]

Bug Report

Current Behavior

If a bianry operator like >= appears directly after TypeScript as assertion, a wrong SyntaxError occurs.

Input Code

function foo(x: any) {
	return x as number >= 0;
}

The above code causes the following SyntaxError:

{ SyntaxError: test.ts: Unexpected token (2:22)
  1 | function foo(x: any) {
> 2 |   return x as number >= 0;
    |                       ^
  3 | }
  4 | 

Expected behavior/code

No SyntaxError should occur.

Babel Configuration (babel.config.js, .babelrc, package.json#babel, cli command, .eslintrc)

• Filename: .babelrc

{
  "presets": ["@babel/preset-typescript"]
}

Environment

  System:
    OS: Linux 4.4 Ubuntu 14.04.5 LTS, Trusty Tahr
  Binaries:
    Node: 10.15.1 - ~/local/lib/node-v10.15.1-linux-x64/bin/node
    Yarn: 1.22.4 - ~/local/lib/node-v10.15.1-linux-x64/bin/yarn
    npm: 6.9.0 - ~/local/lib/node-v10.15.1-linux-x64/bin/npm
  npmPackages:
    @babel/cli: ^7.8.4 => 7.8.4 
    @babel/core: ^7.9.0 => 7.9.0 
    @babel/preset-typescript: ^7.9.0 => 7.9.0 

[babel-bot]

Hey @woongsikchoi! We really appreciate you taking the time to report an issue. The collaborators on this project attempt to help as many people as possible, but we're a limited number of volunteers, so it's possible this won't be addressed swiftly.

If you need any help, or just have general Babel or JavaScript questions, we have a vibrant Slack community that typically always has someone willing to help. You can sign-up here for an invite."

[nicolo-ribaudo]

@DanielRosenwasser What is the precedence of the as operator? It seems like it has very different precedences on the left and on the right, but I'm not sure about it.

Specifically, on the right (EDIT: I initially wrote left here) is it higher or lower than relational operators? I'm asking because from my experiments it has an higher precedence than > and lower precedence than <, but > and < should have the same precedence.

a as b > c > +d; // This is parsed as two `>` operators, and an unary `+`
a as b < c > +d; // This is parsed as a sum between (a as b<c>) and d

Also, is it correct that on the left it is between relational operators and equality operators?

[woongsikchoi]

The same problem occurs also for the nullish coalescing operator ??.

[ghost]

Also dealing with this bug. JSON.parse(value) as unknown ?? undefined throws a syntax error.

[JLHwung]

The same problem occurs also for the nullish coalescing operator ??.

Can you open a new issue? They have different root causes. @woongsikchoi

Never mind I have fixed both of them.