Not all empty where clauses are removed

[scottmcm]

trait Foo where {}
struct Bar where {}
impl<> Foo<> for Bar<> where {}

formats to

trait Foo {}
struct Bar
where
{}
impl Foo for Bar where {}

https://play.rust-lang.org/?edition=2018&gist=3e0a3b133c330b399f45a4fac98c518f

I would have expected that all the empty where clauses were removed, not just the one on the trait, for an output like

trait Foo {}
struct Bar {}
impl Foo for Bar {}