## [`TrustedLen`](https://doc.rust-lang.org/std/iter/trait.TrustedLen.html)
When deriving for enum like the following:
```rust
#[derive(TrustedLen)]
enum Enum {
A(A),
B(B),
}
```
Code like this will be generated:
```rust
enum Enum {
A(A),
B(B),
}
impl ::core::iter::TrustedLen for Enum
where
A: ::core::iter::TrustedLen,
B: ::core::iter::TrustedLen- ::Item>,
{}
```