Tracking issue for RFC 2298, `?` repetition in macro rules

[Centril]

This is a tracking issue for RFC 2298 (rust-lang/rfcs#2298).

Status

• RFC accepted
• Preliminary implementation started (Implement ? macro repetition #47752)
• Preliminary implementation available
• Stabilization proposed
• Stabilized

Known bugs

None.

Unresolved questions to be answered before stabilization

• Should the ? Kleene operator accept a separator? Adding a separator is completely meaningless (since we don't accept trailing separators, and ? can accept "at most one" repetition), but allowing it is consistent with + and *. Currently, we allow a separator. We could also make it an error or lint.

[kennytm]

🤔 Duplicate of #48075?

[mark-i-m]

Yep it is a duplicate

[Centril]

Hmm... missed that tracking issue. I'll close that one since it is easier =)
( Copied the text from the other issue, .. )

[kennytm]

The issue number in

rust/src/libsyntax/feature_gate.rs

Line 448 in 29f5c69

(active, macro_at_most_once_rep, "1.25.0", Some(48075)),

will need to be updated in this case...

[Centril]

Oh damn... Less work to fix the RFC I guess... reopening that one then. =P