E0016: Unknown Struct

You referenced a struct that hasn't been defined.

Example

fn main() {
    let p = Point { x: 1, y: 2 };  // Error: unknown struct `Point`
}

How to fix

Define the struct before using it:

struct Point {
    x: i64,
    y: i64,
}

fn main() {
    let p = Point { x: 1, y: 2 };  // OK
}

Or check for typos in the struct name.