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Comments on Why does the types returned by 'valueOf()' are incompatible with the type `Partial<Temporal.PlainDate>`?

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Why does the types returned by 'valueOf()' are incompatible with the type `Partial<Temporal.PlainDate>`? [closed]

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Closed as unclear by Karl Knechtel‭ on Jun 7, 2025 at 21:23

This question cannot be answered in its current form, because critical information is missing.

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This code:

type A = Partial<Temporal.PlainDate>;
const a: A = { day: 1, month: 1, year: 2025 }

yields this error:

Type '{ day: number; month: number; year: number; }' is not assignable to type 'Partial<PlainDate>'.
  The types returned by 'valueOf()' are incompatible between these types.

      The 'Object' type is assignable to very few other types. Did you mean to use the 'any' type instead?

I expect the type check to pass. In my understanding, Partial<X> is a type with all properties of X set to optional, so a should have no error. If this is the intended restriction, then how can I create a Partial<Temporal.PlainDate> instance?

const a = new Temporal.PlainDate(2025, 1, 1) works. I just wonder why using Partial doesn't work here. Reading Temporal.PlainDate.prototype.valueOf() doesn't help.

typescript deno temporal

posted over 1 year ago

CC BY-SA 4.0

1y ago

Ooker‭

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2 comment threads

Why this is unclear (3 comments)

I wonder if using `new Temporal.PlainDate(year, month, day)` instead of that object literal works. (2 comments)

Karl Knechtel‭ wrote over 1 year ago

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What do you expect to happen when the code runs? For example, do you expect that const a: A = { day: 1, month: 1, year: 2025 } should cause a to become an instance of the Partial<Temporal.PlainDate> class (constructing it from the values in the object)? Or do you just expect the type check to pass? Where the error message says "Type '{ day: number; month: number; year: number; }' is not assignable to type 'Partial'.", was this unclear to you? Or rather - why do you expect that it should be assignable? What should that assignment mean?

Aside from this - are you actually asking about a design decision to disallow the assignment? (If so, are you asking about how Typescript works, or are you asking about how the assignment works?) Or are you actually asking a how-to question, about how to create the Partial<Temporal.PlainDate> instance you want?

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Comments on Why does the types returned by 'valueOf()' are incompatible with the type `Partial<Temporal.PlainDate>`?

Why does the types returned by 'valueOf()' are incompatible with the type Partial<Temporal.PlainDate>? [closed]

2 comment threads

Why does the types returned by 'valueOf()' are incompatible with the type `Partial<Temporal.PlainDate>`? [closed]