E0017: Unknown Enum

You referenced an enum that hasn't been defined.

Example

fn main() {
    let s = Status::Active;  // Error: unknown enum `Status`
}

How to fix

Define the enum before using it:

enum Status {
    Active,
    Inactive,
}

fn main() {
    let s = Status::Active;  // OK
}

Or check for typos in the enum name.