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!

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