macros: Add base functions to check for follow-set ambiguities

Rust does not allow for all macro fragments to be followed by any kind
of tokens: We must check tokens following those fragments that might
contain restrictions and make sure that they are allowed, conforming to
the Macro Follow-Set Ambiguity specification

Co-authored-by: philberty <philip.herron@embecosm.com>

macro-frag-spec: Transform enum into a class

This allows us to add methods on the fragment specifier, which are
needed to make sure that follow-set ambiguities are respected

tests: Add tests for forbidden follow-up tokens

This also fix a test that was previously accepted but invalid: rustc
also rejected it

0 files changed, 0 insertions, 0 deletions