Advanced-mode `update T set x = 42 --all-rows` parsed the `--all-rows`
DSL flag as the arithmetic `42 - -all - rows` over phantom columns
`all`/`rows` (Amendment 3's counter-example), masked only by the engine's
`--` comment leniency. The playground supports no `--` line comment, so
this was a misparse (ADR-0027: flag input known to fail at runtime).
Fix: walk_punct refuses a `-` that begins an adjacent `--`. Only the SQL
expression uses Node::Punct('-'), so this is scoped to it. The SET
expression then stops, the SQL UPDATE shape fails, and dispatch falls
back to the DSL Update { AllRows } — symmetry with delete … --all-rows.
Behaviour: `42 --all-rows` → DSL Update{AllRows}; spaced `42 - -3` stays
SqlUpdate (= 45, preserved); adjacent `42--3` → parse error (contrived;
no `--` comment support).
Tests: inverted parse test (+ arithmetic-preserved + adjacent-error
assertions); new full-pipeline update_all_rows_flag_in_advanced_updates_every_row.
Suite 1963/0/1; clippy clean.
claude@clouddev1
9a23e28f30