# Error code E0639

This error indicates that the struct, enum or enum variant cannot be instantiated from outside of the defining crate as it has been marked as `non_exhaustive` and as such more fields/variants may be added in future that could cause adverse side effects for this code.

Erroneous code example:

ⓘ

    #[non_exhaustive]
    pub struct NormalStruct {
        pub first_field: u16,
        pub second_field: u16,
    }

    let ns = NormalStruct { first_field: 640, second_field: 480 }; // error!

Run

It is recommended that you look for a `new` function or equivalent in the crate’s documentation.

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