Exact does not work with Opaque after 2.19.0

[eugene-mohc]

Exact no longer works when there are any object properties which have a type created using Opaque. This used to work using version 2.18.0 and lower.

type SpecialName = Opaque<string, "special name">;

type OnlyAcceptName = {
  name: SpecialName;
};

function onlyAcceptNameImproved<T extends Exact<OnlyAcceptName, T>>(args: T) {}

onlyAcceptNameImproved({
  // Error: Type 'SpecialName' is not assignable to type 'never'
  name: "name" as SpecialName
});

Example using type-fest 2.18.0: https://codesandbox.io/s/twilight-shape-bc391p?file=/src/index.ts

Same example using latest version: https://codesandbox.io/s/boring-morse-96egn3?file=/src/index.ts

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[sindresorhus]

Most likely this change: edcad04

[sindresorhus]

// @zorji

[zorji]

Sorry for the late reply. Let me have a look.

[zorji]

Hi @eugene-mohc

Sorry I am not familiar with Opaque type and what's its use case but looks like it's trying to solve a similar issue that this Exact type was trying to solve. By reading the definition of Opaque type, I am not sure whether it's because the internal details are hidden so it's not accessible and compare.

I am wondering whether the solution to check if it's an Opaque type and return the type as it is can solve the issue.

Would you able to checkout the change in this branch and see if that fixes the issue for you? #525

[eugene-mohc]

Hi and thank you, that has solved it for my use cases. I was only using Opaque with strings and numbers though, so I can't comment on how it would work with any others.