[Bug]: Edge case in TSX: `<T,>(t: T) => t`

💻

• Would you like to work on a fix?

How are you using Babel?

Programmatic API (babel.transform, babel.parse)

Input code

const { transformSync } = require('@babel/core')

let result = transformSync(`
  const fn = <T,>(t: T) => t;
`, {
  babelrc: false,
  configFile: false,
  parserOpts: {
    plugins: [
      'jsx',
      'typescript',
    ]
  },
})

console.log(result.code)

Configuration file name

No response

Configuration

No response

Current and expected behavior

The current output:

const fn = <T>(t: T) => t;

This is valid in TS, but invalid in TSX, because <T> is treated as a tag in TSX context.

Expected output:

const fn = <T,>(t: T) => t;

Environment

  System:
    OS: macOS 11.5.2
  Binaries:
    Node: 16.9.1 - /usr/local/bin/node
    Yarn: 1.22.11 - /usr/local/bin/yarn
    npm: 7.23.0 - /usr/local/bin/npm

Possible solution

No response

Additional context

Original Issue: vitejs/vite#4949.

[ozanhonamlioglu]

Yes, yarn jest generator works without problems on my machine 🤔

Okay, never mind then, probably it is related to my env. I actually started to dig in already, and it is going well and will update you soon I hope. Thanks

[nicolo-ribaudo]

Yes, yarn jest generator works without problems on my machine 🤔