[Presets: React + Typescript] Interface with generic method fails transpilation

[lukeggchapman]

bug report

Input Code

This is only an issue when using both the react and typescript presets.

interface I {
    <T>(p: T): T
}

Repl Link

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

{
    "presets": [
        "@babel/react",
        "@babel/typescript"
    ],
}

Expected Behavior

It should not throw and error.

Current Behavior

It throws:

{ SyntaxError: ./src/test.tsx: Unexpected token (2:4)

  1 | interface I {
> 2 |     <T>(p: T): T
    |     ^
  3 | }
  4 |

Possible Solution

Similar issue with generic methods: #6665
Similar fix for generic methods: #7225
Duplicate but closed Issue: #7158

Context

Your Environment

software	version(s)
Babel	7.0.0-beta.40
preset-react	7.0.0-beta.40
preset-typescript	7.0.0-beta.40
node	8.9.0
npm	5.5.1
Operating System	OSX

[babel-bot]

Hey @lukeggchapman! 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.

[jon-lp]

+1 also encountering

[jon-lp]

@lukeggchapman FWIW moving the function interface declaration into a separate file.d.ts file seemed to make everything happy:
– Webpack/Babel successfully compiles
– tsc type check works with that interface
– VSCode sees/follows it and has no errors/warnings
hope that helps!

[Tsury]

Also encountering this.

[danez]

Fixed by #9058