wrap_comments = true breaks markdown tables

[jhpratt]

To be 100% clear: I am aware this is a duplicate. It appears this is a regression, as presumably it worked at some point (the original is closed).

See #4210. This exact situation occurs on latest rustfmt.

Describe the bug

Running rustfmt --config wrap_comments=true example.rs on

/// doc
///
/// Table that is > 80 symbols:
///
/// | table | xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx |
/// |-------|--------------------------------------------------------------------|
/// | val   | x                                                                  |
struct Item;

turns it into

/// doc
///
/// Table that is > 80 symbols:
///
/// | table | xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
/// |
/// |-------|--------------------------------------------------------------------|
/// | val   | x
/// |
struct Item;

This breaks the markdown.

Meta

• rustfmt version: rustfmt 1.4.29-nightly (70ce182 2020-12-04)
• From where did you install rustfmt?: rustup
• How do you run rustfmt: Reproducible with just plain old rustfmt

Related:

• Don't wrap comments that are part of a table #4214, which presumably fixed the issue initially. The code appears to be present here, but for some reason it's not being used (I haven't dug into this)
• [unstable option] wrap_comments #3347 for stabilization. This is likely one of the final blockers.

[jhpratt]

@rustbot modify labels to +unstable option, +only-with-option

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[calebcartwright]

It appears this is a regression, as presumably it worked at some point (the original is closed).

Closing because this is both a duplicate and incorrect. I've also added the backport pending label to #4210 for clarity