macro_rules should expose accessors for total iteration count and current iteration number

[pnkfelix]

macro_rules should expose accessors that map each Kleene-star/plus $(pat)<delim>* / $(pat)<delim>+ to a total iteration count and the current iteration number within the expansion template.

See RFC PR #88 for discussion, including on proposed syntax in the RFC itself, as well as much discussion about alternative syntaxes in the associated discussion.

[blaenk]

This is great; the motivating example is very convincing.

[pnkfelix]

The declarative macro repetition counts projects has taken ownership of this problem: rust-lang/lang-team#57 ; see their current work at #3086

[c410-f3r]

This issue can probably be closed now

[kennytm]

closing as duplicate of #3086. see rust-lang/rust#83527 for the tracking issue.