lint comparison operations on bool

[oli-obk]

We already have bool_comparison, but it only lints equality. we should extend it to also cover inequality and ordering operations.

Inspired by the wonderful https://twitter.com/chordbug/status/1064932667089670144?s=20

Some care needs to be taken to produce good suggestions.

[waynr]

@oli-obk are you saying that clippy should suggest replacing inequality and ordering operations with equivalent minimal boolean operations? eg

if y != true { "yes" } else { "no" };
// should be
if !y { "yes" } else { "no"};

if x < y { "yes" } else { "no" };
// should be
if !x && y { "yes" } else { "no"};

[oli-obk]

yes

[lucasloisp]

I would be glad to work on this! I'll give it a try

[phansch]

With #3473 merged, this lint now additionally checks for !=.

[detrumi]

The lint has been added, so I think this issue can be closed?