AfterShip / clickhouse-sql-parser / 28727429863

Pull #282

github

Split keywords into reserved and non-reserved sets

Revives #275 rebased onto current master (post-#276/#277 renames) and
addresses both review regressions.

matchTokenKind previously coerced every keyword token to match
TokenKindIdent, so any keyword could silently fill an identifier slot:
`SELECT a FROM WHERE b = 1` parsed as `SELECT a AS FROM WHERE b = 1`.

- New reservedKeywords set: statement/clause starters and expression
  operators no longer match identifier positions, so a missing name
  fails fast at the clause keyword. All other keywords stay usable as
  bare identifiers.
- parseAnyKeyword accepts any keyword - reserved or not - in positions
  where context has already proven the token is a name: after AS, after
  a dot in a qualified name, or a lookahead-disambiguated select item.

Review fixes on top of the original branch:
- Operator keywords stay callable as ClickHouse functions when followed
  by '(': and(a, b), or(a, b), in(1, [1]), like(s, p), ilike(s, p).
  parseIdentOrFunction now accepts a keyword name in that case.
- Reserved keywords are accepted as aliases after AS in expression
  lists (`SELECT (1 AS from)`, `sum(x AS from)`), ORDER BY
  (`ORDER BY x AS from`) and non-parenthesized CTEs
  (`WITH 1 AS from SELECT from`), per review suggestions.

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

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