[no-unused-vars] v4 false positive with generic inference - with isolated reproduction repo

[willheslam]

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I have read the FAQ and my problem is not listed.

Repro
https://github.com/willheslam/typescript-unused-var-reprod
npm run lint

{
  "rules": {
    "@typescript-eslint/no-unused-vars": 1
  }
}

// eslint-disable-next-line @typescript-eslint/no-explicit-any
type UnionToIntersection<U> = (U extends any ? (k: U) => void : never) extends (
  k: infer I
) => void
  ? I
  : never

Expected Result

No linting issues

Actual Result

3:12  warning  'I' is defined but never used  @typescript-eslint/no-unused-vars

✖ 1 problem (0 errors, 1 warning)

Additional Info

Versions

package	version
@typescript-eslint/eslint-plugin	4.0.1
@typescript-eslint/parser	4.0.1
TypeScript	4.0.2
ESLint	7.8.0
node	12.14.1

[blair]

I'm seeing a similar warning in this code:

// https://stackoverflow.com/a/51955852/
type KnownKeys<T> = {
    [K in keyof T]: string extends K ? never : number extends K ? never : K
} extends { [_ in keyof T]: infer U } ? U : never;

gives

  4:35  error  'U' is defined but never used  @typescript-eslint/no-unused-vars

[StasNemy]

export type InferActionsTypes<T> = T extends { [keys: string]: (...args: any[]) => infer U } ? U : never;
'U' is defined but never used @typescript-eslint/no-unused-vars
How about this. Help!