--skip-children not working?

[nrc]

[santiago@archlinux rust1 (diagnostic-suggest-drop-in-reverse)]$ git status
On branch diagnostic-suggest-drop-in-reverse
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   src/librustc_mir/borrow_check/error_reporting.rs
    modified:   src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs

no changes added to commit (use "git add" and/or "git commit -a")
[santiago@archlinux rust1 (diagnostic-suggest-drop-in-reverse)]$ rustfmt --skip-children src/librustc/mir/mod.rs
[santiago@archlinux rust1 (diagnostic-suggest-drop-in-reverse)]$ git status
On branch diagnostic-suggest-drop-in-reverse
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   src/librustc/mir/cache.rs
    modified:   src/librustc/mir/interpret/error.rs
    modified:   src/librustc/mir/interpret/mod.rs
    modified:   src/librustc/mir/interpret/value.rs
    modified:   src/librustc/mir/mod.rs
    modified:   src/librustc/mir/mono.rs
    modified:   src/librustc/mir/tcx.rs
    modified:   src/librustc/mir/traversal.rs
    modified:   src/librustc/mir/visit.rs
    modified:   src/librustc_mir/borrow_check/error_reporting.rs
    modified:   src/librustc_mir/borrow_check/nll/explain_borrow/mod.rs

no changes added to commit (use "git add" and/or "git commit -a")

[topecongiro]

You need to pass --unstable-features as well.

[topecongiro]

I think rustfmt should warn users when unstable options are passed without --unstable-features.