An import was unresolved.

Erroneous code example:

```compile_fail,E0432
use something::Foo; // error: unresolved import `something::Foo`.
```

Paths in `use` statements are relative to the crate root. To import items
relative to the current and parent modules, use the `self::` and `super::`
prefixes, respectively. Also verify that you didn't misspell the import
name and that the import exists in the module from where you tried to
import it. Example:

```
use self::something::Foo; // ok!

mod something {
    pub struct Foo;
}
# fn main() {}
```

Or, if you tried to use a module from an external crate, you may have missed
the `extern crate` declaration (which is usually placed in the crate root):

```
extern crate core; // Required to use the `core` crate

use core::any;
# fn main() {}
```