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### What it does
Checks for deriving `Ord` but implementing `PartialOrd`
explicitly or vice versa.
### Why is this bad?
The implementation of these traits must agree (for
example for use with `sort`) so it’s probably a bad idea to use a
default-generated `Ord` implementation with an explicitly defined
`PartialOrd`. In particular, the following must hold for any type
implementing `Ord`:
```
k1.cmp(&k2) == k1.partial_cmp(&k2).unwrap()
```
### Example
```
#[derive(Ord, PartialEq, Eq)]
struct Foo;
impl PartialOrd for Foo {
...
}
```
Use instead:
```
#[derive(PartialEq, Eq)]
struct Foo;
impl PartialOrd for Foo {
fn partial_cmp(&self, other: &Foo) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Foo {
...
}
```
or, if you don't need a custom ordering:
```
#[derive(Ord, PartialOrd, PartialEq, Eq)]
struct Foo;
```
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