Returned object is not assignable to defined return type

[zaunermax]

🐞 Bug Report

Describe the bug

I seem to run into a bug, where Update works flawlessly on static types, but breaks on generic types.

Reproduce the bug

enum TypeEnum {
	FOO = 'foo',
	BAR = 'bar',
}

type HasCompany = { company: { type: string } };
type UpdatedHasCompany = Object.P.Update<HasCompany, ['company', 'type'], TypeEnum>;

// this works flawlessly
const test: UpdatedHasCompany = { company: { type: TypeEnum.BAR } };

// this does not work!
const updateType = <T extends HasCompany>(
	e: T,
): Object.P.Update<T, ['company', 'type'], TypeEnum> => ({
	...e,
	company: {
		type: TypeEnum.BAR, // here i would have a conversion function
	}
});

Expected behavior

P.Update should work with generics. Not sure if this is a TS limitation though 🤔

Additional context

toolbelt version 8.0.7 - Typescript version 4.0.3

[millsp]

Hey @zaunermax, thanks for reporting this. This is a limitation where TypeScript is not able to predict the output in the presence of a generic type. You will have to override and cast your returned value to any.

[zaunermax]

Ok thanks for clarifying, sorry to having bothered you 🙌

[millsp]

My pleasure, no problem. I'm adding this to the wiki.

Cheers