An unknown field was specified into a structure.
Erroneous code example:
```compile_fail,E0560
struct Simba {
mother: u32,
}
let s = Simba { mother: 1, father: 0 };
// error: structure `Simba` has no field named `father`
```
Verify you didn't misspell the field's name or that the field exists. Example:
```
struct Simba {
mother: u32,
father: u32,
}
let s = Simba { mother: 1, father: 0 }; // ok!
```