rustfmt-nightly 1.1.1

mod m { struct S where A: B; }

mod n { struct Foo where A: B { foo: usize } }

mod o { enum Bar where A: B { Bar } }

mod with_comments {
  mod m { struct S /* before where */ where A: B; /* after where */ }
  
  mod n { struct Foo /* before where */ where A: B /* after where */ { foo: usize } }
  
  mod o { enum Bar /* before where */ where A: B /* after where */ { Bar } }
}