Rustfmt deletes comments in trait declarations

[luliic2]

Describe the bug
I have the following piece of code:

pub trait Foo<'a, 'b>
where
    'a: 'b, // Some random comment
{
}

Which rustfmt reformats to:

pub trait Foo<'a, 'b>
where
    'a: 'b,
{
}

Deleting the comment

To Reproduce

Run cargo fmt with the first code block results in the second code block

Expected behavior

The comment should not be deleted

Meta

• rustfmt version: rustfmt 1.4.25-stable. Reddit user u/m0rphism also reports it can be reproduced with rustfmt 1.4.9-nightly
• From where did you install rustfmt?: rustup
• How do you run rustfmt: cargo fmt & from vscode

[karyon]

repro'd with 1.4.38

[ytmimi]

Just making a note that #4292 is the relevant backport PR, but #4213 is also related to comments and where clauses, and it might be nice to backport these together.

[ytmimi]

The issue also seems partially related to #4649, however #4649 also describes that comments are dropped between where clauses and function bodies.

[calebcartwright]

The issue also seems partially related to #4649, however #4649 also describes that comments are dropped between where clauses and function bodies.

If there's a separate case that won't be covered by backporting a prior fix let's be sure to note that (preferably with a separate issue for tracking)