the Draft<T> could not use the keyof T type

[Rey Wang]

you can see an code example here:
code sandbox

function ChangeState<T extends Record<string, any>, M extends keyof T>(
  state: T,
  field: M,
  value: T[M]
) {
  return produce(state, (draftState) => {
    draftState[field] = value;
    // Type 'M' cannot be used to index type 'Draft<T>'
  });
}

the keyof T should be used by Draft<T>

[Michel Weststrate]

See `castDraft` https://immerjs.github.io/immer/typescript#cast-utilities

…

On Thu, Mar 17, 2022 at 11:14 AM Rey Wang ***@***.***> wrote: you can see an code example here: code sandbox <https://codesandbox.io/s/typescript-playground-export-forked-jf764x?file=/index.ts> function ChangeState<T extends Record<string, any>, M extends keyof T>( state: T, field: M, value: T[M] ) { return produce(state, (draftState) => { draftState[field] = value; // Type 'M' cannot be used to index type 'Draft<T>' }); } the keyof T should be used by Draft<T> — Reply to this email directly, view it on GitHub <#918>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN4NBB7VBTQXTJ3GNWS5BDVAMH3HANCNFSM5Q6UMC2A> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[p2k]

I'm sorry but how does castDraft help here? draftState is already of the type Draft<T> using the cast would produce Draft<Draft<T>>.

I have a similar problem:

function ChangeStringState<M extends string>(
  state: Record<M, string>,
  field: M,
  value: string,
) {
  return produce(state, (draftState) => {
    draftState[field] = value;
    // Type 'M' cannot be used to index type 'Draft<Record<M, string>>'
  });
}

[Luca Fanselau]

Yeah same here, is there a way to use a generic keyof M parameter to index the Draft type?