refactor(syntax): generalize the macro repetition separator node

[orizi]

MacroRepetition.separator was OptionTerminalComma, baking the only separator
the parser currently accepts into the grammar. Replace it with
OptionMacroRepetitionSeparator, wrapping a MacroRepetitionSeparator struct
whose single token child is a TokenNode — the codegen's all-terminals enum —
so the grammar can hold any terminal as a separator.

An option must wrap a node that has a SyntaxKind, and enums do not get one
(generate_kinds_code filters NodeKind::Enum out), hence the small wrapper
struct — the same reason TokenTreeLeaf wraps TokenNode. The syntax crate is
regenerated by generate-syntax, not hand-edited.

Behavior is unchanged. The parser still accepts only TerminalComma in that
slot, and the semantic matcher and expansion still treat only a comma as a
separator, now via a single repetition_separator helper that returns None
for any other token — the same branch as "no separator" — rather than
panicking, so loosening the parser later cannot introduce a panic.
$($x:ident);* is still rejected with the same Missing macro repetition operator diagnostic. The only golden churn is in the parser partial_trees:
OptionTerminalCommaEmpty becomes OptionMacroRepetitionSeparatorEmpty, and
existing comma separators gain the MacroRepetitionSeparator level. No semantic
golden changed.

TokenTreeRepetition.separator is deliberately left as OptionTerminalComma.
The adjacent TODO(Dean): Remove TokenTreeRepetition and TokenTreeParam (it's redundant) intends to delete that node outright, so migrating it would be churn
on code slated for removal and would couple the call-site token-tree grammar to
the macro-rule grammar that TODO wants to disentangle. That refactor is
explicitly not folded in here; .add_option("TerminalComma") stays for it and
becomes dead only once it lands.

The unreachable!() on ast::MacroParamKind::Missing in macro_declaration.rs
is not made reachable by this change, so no guard was added. The accepted token
language is identical before and after, so no new tree shape is produced, and
the separator slot is structurally disjoint from ParamKind. Checked
empirically that it also stays unreachable in general: macro m { ($x:foo) => { 1 }; } reports Missing tokens. Expected a macro rule parameter kind. and the
rule is then dropped by the descendants(..).any(is_missing) filter in
priv_macro_declaration_data, so the matcher never converts a missing param
kind. That filter is unaffected here — OptionMacroRepetitionSeparatorEmpty is
a plain struct kind, not a missing kind, exactly like the
OptionTerminalCommaEmpty it replaces.

Co-Authored-By: Claude Fable 5 noreply@anthropic.com

[reviewable-StarkWare]

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[orizi]

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• fix(semantic): reject a + expansion repetition over zero groups #10315
• doc(semantic): document the macro expansion error arms as defensive #10314
• fix(semantic): reject a trailing macro repetition separator like rustc #10313
• feat(semantic): match and emit non-comma macro repetition separators #10312
• feat(parser): accept any single-token macro repetition separator #10311
• refactor(syntax): generalize the macro repetition separator node #10310 👈 (View in Graphite)
• fix(semantic): parenthesize an expression capture spliced into an expansion #10309
• fix(semantic): keep the trailing trivia of an expansion's placeholders and blocks #10308
• fix(semantic): capture an expr placeholder by what the parser consumed #10307
• test(semantic): pin the macro matcher behaviors that already agree with rustc #10306
• fix(semantic): reject a pattern that follows an expr placeholder with a token it would swallow #10305
• fix(semantic): reject the malformed macro rule declarations that silently do nothing #10304
• fix(semantic): match a pattern subtree only against a call subtree with the same delimiters #10303
• fix(semantic): reject a macro rule pattern that reuses a placeholder name #10302
• main

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[cursor]

PR Summary

Low Risk
Structural syntax-tree refactor with behavior-preserving semantic handling; parser still only accepts commas and macro matching/expansion logic is centralized in one helper.

Overview
Replaces MacroRepetition.separator from OptionTerminalComma with OptionMacroRepetitionSeparator, wrapping a MacroRepetitionSeparator node whose token child is a generic TokenNode. The grammar can represent any terminal as a separator; the parser still only accepts a comma today, and semantics route through a new repetition_separator helper that treats non-comma tokens like “no separator” instead of assuming a comma-only shape.

Parser partial-tree goldens pick up the extra wrapper level; observable macro behavior and diagnostics are intended to stay the same. TokenTreeRepetition is unchanged on purpose.

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[eytan-starkware]

@eytan-starkware+AGNT made 2 comments.
Reviewable status: 0 of 8 files reviewed, 1 unresolved discussion (waiting on eytan-starkware, orizi, and TomerStarkware).

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a discussion (no related file):
Note: the comments below are from an automatic orizi-review run (Claude agents reviewing in Ori's style, findings adversarially verified before posting). Treat with the usual bot skepticism.

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crates/cairo-lang-syntax-codegen/src/cairo_spec.rs line 911 at r1 (raw file):

    )
    .add_option("MacroRepetitionSeparator")
    .add_option("TerminalComma")

after this change OptionTerminalComma exists only for TokenTreeRepetition (l.825). move it up next to that node so it's obvious it dies together with the TODO(Dean): Remove TokenTreeRepetition.