No compiler error from method with variant

[paarthenon]

No compiler error from method with variant

[paarthenon]

Hi there! Could you let me know what version of TypeScript and Variant this is referencing? I'm using Variant 2.1 with TS 4.1 and I am experiencing a compiler error on the last line as you might expect.

Type '{ type: "cat"; }' is not assignable to type '{ type: "dog"; }'.ts(2345)

Full error:

Argument of type '(dog: { type: "dog"; }) => SumType<{ dog: VariantCreator<"dog", () => {}, "type">; cat: VariantCreator<"cat", () => {}, "type">; }, "type">' is not assignable to parameter of type '(value: SumType<{ dog: VariantCreator<"dog", () => {}, "type">; cat: VariantCreator<"cat", () => {}, "type">; }, "type">, index: number, array: SumType<...>[]) => SumType<...>'.
  Types of parameters 'dog' and 'value' are incompatible.
    Type 'SumType<{ dog: VariantCreator<"dog", () => {}, "type">; cat: VariantCreator<"cat", () => {}, "type">; }, "type">' is not assignable to type '{ type: "dog"; }'.
      Type '{ type: "cat"; }' is not assignable to type '{ type: "dog"; }'.ts(2345)

If you are indeed using these same versions, it might be a compiler caching issue. If you are using VS Code could you try ctrl+shift+P and then select the TypeScript: Restart TS Server option. There should be a similar option for other editors.

Thanks for trying out the library. I hope we can get this figured out.

[hellos3b]

I'm on Variant 2.1.0 and TS 4.2.3 on VSCode

I've also got an example of it on code sandbox: https://codesandbox.io/s/typescript-forked-gjgvk?file=/src/index.ts:283-284

I've tried using Extract and a direct ref too with the same issue

declare function bark(dog: Extract<typeof Animal, {type: "dog"}>): Animal;
declare function bark(dog: typeof Animal.dog): Animal;

[paarthenon]

I believe this has to do with the strictFunctionTypes tsconfig flag.

https://www.typescriptlang.org/tsconfig#strictFunctionTypes

More context: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-6.html#strict-function-types

Enabling that flag in your code sandbox looks like it will raise the error. I tend to run with "strict": true, which will include it.

[hellos3b]

Ah, sweet! Always forget about that setting, thanks for reminding me.