2 Checks for deriving `Hash` but implementing `PartialEq`
3 explicitly or vice versa.
6 The implementation of these traits must agree (for
7 example for use with `HashMap`) so it’s probably a bad idea to use a
8 default-generated `Hash` implementation with an explicitly defined
9 `PartialEq`. In particular, the following must hold for any type:
12 k1 == k2 ⇒ hash(k1) == hash(k2)
20 impl PartialEq for Foo {