fix: recursive T for WritableDraft

[unional]

This contains a proper fix for #990

Added tests for the type check.

Included #1196 as I don't want to see the type errors in the tests.

[coveralls]

Pull Request Test Coverage Report for Build 20424663455

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 42.865%

---

Totals
Change from base Build 20394930238:	-0.01%
Covered Lines:	1678
Relevant Lines:	4771

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💛 - Coveralls

[mweststrate]

Looks great, thanks!

[github-actions]

🎉 This PR is included in version 11.1.3 🎉

The release is available on:

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• GitHub release

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[wereHamster]

Looks like this change is causing the following code to fail:

function Test<A>() {
  produce(
    (draft) => {
      draft.prop = undefined; // <- type error here
    },
    { prop: undefined as undefined | A },
  );
}

Type error on indicated line:

Type undefined is not assignable to type A | undefined extends infer V ? V extends object ? Draft : V : never

[unional]

Looks like this change is causing the following code to fail:

I can reproduce it. It seems like the type cannot be resolved partially like this.

Is there a particular use case for this? Is there a reason to declare the type like this rather than as a whole like:

	function Test<A extends { prop: undefined }>() {
		produce(
			(draft) => {
				draft.prop = undefined;
			},
			{ prop: undefined } as A,
		);
	}

[wereHamster]

My full code is more like this:

function MultiLineChart<A extends TDatum<{}>>(props: Props<A>) {
  const [state, mutate] = useImmer({
    hovered: undefined as undefined | A,
  });

  const resetHover = React.useCallback(() => {
    mutate((draft) => {
      draft.hovered = undefined; // <- type error here
    });
  }, [mutate]);
}

Interestingly, the following (which is quite close to your code) also errors:

function Test<A>() {
  type S = { prop: undefined | A }

  produce(
    (draft) => {
      draft.prop = undefined; // <- type error here
    },
    { prop: undefined } as S,
  );
}

[unional]

The issue is S is being distributed to Draft<S> and S.
Since TypeScript cannot determine the type of A during static analysis, it fails.

I have a fix to defer the analysis. Let me create a PR.