```
pub trait Shl<Rhs = Self> {
type Output;
// Required method
fn shl(self, rhs: Rhs) -> Self::Output;
}
```

## Expand description

The left shift operator `<<`

. Note that because this trait is implemented
for all integer types with multiple right-hand-side types, Rust’s type
checker has special handling for `_ << _`

, setting the result type for
integer operations to the type of the left-hand-side operand. This means
that though `a << b`

and `a.shl(b)`

are one and the same from an evaluation
standpoint, they are different when it comes to type inference.

## §Examples

An implementation of `Shl`

that lifts the `<<`

operation on integers to a
wrapper around `usize`

.

```
use std::ops::Shl;
#[derive(PartialEq, Debug)]
struct Scalar(usize);
impl Shl<Scalar> for Scalar {
type Output = Self;
fn shl(self, Self(rhs): Self) -> Self::Output {
let Self(lhs) = self;
Self(lhs << rhs)
}
}
assert_eq!(Scalar(4) << Scalar(2), Scalar(16));
```

An implementation of `Shl`

that spins a vector leftward by a given amount.

```
use std::ops::Shl;
#[derive(PartialEq, Debug)]
struct SpinVector<T: Clone> {
vec: Vec<T>,
}
impl<T: Clone> Shl<usize> for SpinVector<T> {
type Output = Self;
fn shl(self, rhs: usize) -> Self::Output {
// Rotate the vector by `rhs` places.
let (a, b) = self.vec.split_at(rhs);
let mut spun_vector = vec![];
spun_vector.extend_from_slice(b);
spun_vector.extend_from_slice(a);
Self { vec: spun_vector }
}
}
assert_eq!(SpinVector { vec: vec![0, 1, 2, 3, 4] } << 2,
SpinVector { vec: vec![2, 3, 4, 0, 1] });
```