Should MacroCall include optional ident?

[ehuss]

The current grammar defines a macro call with an IDENT after the !, but libsyntax rejects this in various places.

foo!bar{}

If this is removed, then special support for macro_rules! would need to be added.

[petrochenkov]

Support for defining foo! bar { ... } macros was removed in rust-lang/rust#61606, so the parser needs to be cleaned up too.

macro_rules hasn't been a macro call for yeas, it's treated specially by the parser as well, and it should be treated specially by the grammar.
Also, we may want to support pub on macro_rules items, which would make them more special.

[petrochenkov]

cc rust-lang/rust#62258