Bug Report

• [~] I would like to work on a fix!

Current behavior
Parse error when an explicit type parameter is a generic arrow function

• REPL

Input Code

f<<T>(value: T) => void>(g);

Expected behavior
The type parameter should be stripped from the code:

f(g);

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

• Filename: babel.config.js

{
  "presets": [
    ["@babel/preset-env", { "targets": { "node": "current" } }],
    "@babel/typescript"
  ],
  "plugins": [
    "@babel/plugin-syntax-class-properties"
  ]
}

Environment

• Babel version(s): v7
• Node/npm version: Node 13.8.0/npm 6.13.6
• OS:macOS 10.15.5
• Monorepo: yes
• How you are using Babel: cli

Possible Solution
Note that these two examples both parse correctly:

f< <T>(value: T) => void>(g); // Note the space between the two "<"
f<U, <T>(value: T) => void>(g);

My guess is that the parser thinks it's encountered a << operator. I think C++ also used to have this problem in its parser 😅.

Additional context
TypeScript playground