TS 4.0: jsxFragmentFactory ignored in Preact + TypeScript setup

[ddprrt]

I'm using the new jsxFragmentFactory to make Fragment work in a Preact setup, but TypeScript won't recognize it.

TypeScript Versions: 4.0.0-beta, 4.0.0-dev.20200706

Search Terms: JSX Fragment Factory, Preact

Code

Counter.tsx

import { Fragment, h } from "preact"

import { useState } from "preact/hooks"

type CounterProps = {
  count?: number
}

export function Counter({count = 0}: CounterProps) {
  const [cnt, setCnt] = useState(count)
  return <>
    <p>{cnt}</p>
    <button onClick={() => setCnt((prev) => prev + 1)} type="button">Update</button>
  </>
}

tsconfig.json

{
  "compilerOptions": {
    "target": "esnext",
    "lib": ["DOM", "DOM.Iterable", "esnext"],
    "allowJs": false,
    "skipLibCheck": false,
    "esModuleInterop": false,
    "allowSyntheticDefaultImports": true,
    "strict": true,
    "forceConsistentCasingInFileNames": true,
    "module": "esnext",
    "moduleResolution": "Node",
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true,
    "jsx": "preserve",
    "jsxFactory": "h",
    "jsxFragmentFactory": "Fragment",
    "noUnusedLocals": true
  },
  "include": ["src"]
}

See also:

Expected behavior: TypeScript recognizes that I use <>...</> as a shorthand for the imported Fragment

Actual behavior:
With "noUnusedLocals" set to true, TypeScript throws error TS6133: 'Fragment' is declared but its value is never read.

Playground Link: No playground, but a GitHub repo (https://github.com/ddprrt/preact-vite-ts-playground) -- this is a Vite setup that compiles, but I think this can be ignored for this issue. Editor feedback and running tsc show the actual behavior.

Hope this helps!

[DanielRosenwasser]

Should be quick for us to fix.