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TS2314

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    TS2314

    Generic type needs type arguments

    Generic type 'Box' requires 1 type argument(s).

    The compiler’s own words. Not translated — this is the string you pasted into a search box.

    A generic alias was used without supplying the type parameter it requires.

    Reproduction

    type Box<T> = { value: T }

const box: Box = { value: 1 }

    The build asserts this emits exactly this code.

    Why the compiler says this

    `T` is an input to the type-level function `Box`. Without an argument or a declared default, the checker cannot know which value type the property should contain.

    Fixes

    1. 01
      type Box<T> = { value: T }

const box: Box<number> = { value: 1 }

      Supply the concrete type required at this use site.

    2. 02
      type Box<T = unknown> = { value: T }

const box: Box = { value: 1 }

      Add a safe default only when the generic has a meaningful general case.

    Takeaway

    Every required type parameter needs an argument, just as every required function parameter needs a value.

    Where to go next

    Generic parametersTry it in the Lab
    Errors