Added comment line above any comment that starts with -

[DevinR528]

Any place a comment is added like:

// - 16 because we push in the above seq of instructions

rustfmt turns it into

//
// - 16 because we push in the above seq of instructions

I'm not sure if it's trying to be smart and add newline before what it thinks is a list item in the markdown or something else?

cargo fmt --version
rustfmt 1.4.38-nightly (891ca5f 2021-11-15)

[calebcartwright]

Could you please provide a short, but reproducible example, and also include any non-default configuration options you are using?

I'm unable to reproduce this using as a standalone comment, so suspect there's config and/or context missing.

[DevinR528]

It's wrap_comments = true sorry this should have been obviously helpful info. The problem goes away when turned off.

[ytmimi]

I'm able to reproduce this on the latest master rustfmt 1.4.38-nightly (eee8f041 2021-11-17) with the option wrap_comments=true using a slightly modified mcve:

 // - a

When I run cargo run --bin rustfmt -- --check --config=wrap_comments=true I get this diff

+// 
 // - a

And I get the following error:

error[internal]: left behind trailing whitespace
  |
1 | //
  |   ^
  |
  = note: set `error_on_unformatted = false` to suppress the warning against comments or string literals

warning: rustfmt has failed to format. See previous 1 errors.