Typescript 3.4 as const not working for arrays

[gcangussu]

Bug Report

Current Behavior
Babel's typescript transform plugin doesn't support as const with arrays if those have variables or objects into them. The main Typescript implementation does support it.

Input Code
Here's a quick repo reproducing it: https://github.com/gcangussu/babel-typescript-const-error

But basically this is the problem:

function ok() {
  return ['oi', 42] as const; // Type 'readonly ["oi", 42]'
}

function notOk() {
  const a = 'oi';
  const b = 42;
  return [a, b] as const; // SyntaxError: Only literal values are allowed in constant contexts
}

Expected behavior/code

function notOk() {
  const a = 'oi';
  const b = 42;
  return [a, b] as const; // Type 'readonly ["oi", 42]'
}

Babel Configuration (.babelrc, package.json, cli command)

module.exports = {
  presets: ['@babel/preset-typescript'],
};

Environment

• Babel version: @babel/core 7.4.3, @babel/plugin-transform-typescript 7.4.0
• Node/npm version: node 11.14, yarn 1.15.2
• OS: Ubuntu 18.4
• How you are using Babel:yarn babel index.ts

[babel-bot]

Hey @gcangussu! 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]

Fixed by #9869