The `meta` fragment specifier is considered as a single TT.

[LeoTestard]

At various locations of the FOLLOW sets analysis for macro_rules!, meta is considered as always matching a single TT. This is not the case: ident = ... and ident(...) are both valid metas.

That being said the only consequence of this is that meta can be followed by anything, and I think it's not unreasonable to assume that the syntax of meta will not be expanded in the future... But still, we might want to check that.

[durka]

I think it's not unreasonable to assume that the syntax of meta will not be expanded in the future

It could happen.

[steveklabnik]

Triage: honestly, I'm not good enough with macros to know what exactly the details are here; it seems that #63764 expanded the syntax even with this roadblock.