Used solely by the
count meta-variable expression, counts the outer-most repetitions at a
given optional nested depth.
tree, make sure that all sequences have the same length as the matches for the
appropriate meta-vars in
Lookup the meta-var named
ident and return the matched token tree from the invocation using
the set of matches
item declared on the LHS given an arbitrary Ident
Store the metavariable span for this original span into a side table.
FIXME: Try to put the metavariable span into
SpanData instead of a side table (#118517).
An optimal encoding for inlined spans will need to be selected to minimize regressions.
The side table approach is relatively good, but not perfect due to collisions.
In particular, collisions happen when token is passed as an argument through several macro
calls, like in recursive macros.
The old heuristic below is used to improve spans in case of collisions, but diagnostics are
still degraded sometimes in those cases.
Used by meta-variable expressions when an user input is out of the actual declared bounds. For
example, index(999999) in an repetition of only three elements.
This can do Macro-By-Example transcription.