TS2345: Fails when both branches of a conditional generic are valid

[ArnaudBarre]

TypeScript Version: 4.0.5, 4.1-beta, 4.2.0-dev

Search Terms: TS2345 conditional generic

Code: (Playground Link)

export const DatePicker = <IsClearable extends boolean>({
  value, onChange, isClearable
}: {
  value: string | undefined
  onChange: (
    value: IsClearable extends true ? string | undefined : string,
  ) => void;
  isClearable?: IsClearable;
}) => (
  <>
    <div>{value ?? "Choose"}</div>
    // In an ideal world this one would works, but that's not the biggest issue
    {value && isClearable && <button onClick={() => onChange(undefined!)}>Clear</button>}
    // This one seems more like a bug
    <input type="date" onChange={e => onChange(e.target.value)} />
  </>
);

Expected behavior: No error

Actual behavior: Argument of type 'string' is not assignable to parameter of type 'IsClearable extends true ? string | undefined : string'

[andrewbranch]

Duplicate of #26933