### What it does

Finds items imported through `alloc` when available through `core`.

### Why is this bad?

Crates which have `no_std` compatibility and may optionally require alloc may wish to ensure types are
imported from core to ensure disabling `alloc` does not cause the crate to fail to compile. This lint
is also useful for crates migrating to become `no_std` compatible.

### Example
```
use alloc::slice::from_ref;
```
Use instead:
```
use core::slice::from_ref;
```