Every capture an action receives bundles the raw parsed structure with a callable to evaluate it: node is always available, unevaluated -- what quote returns directly. eval is what an action calls when it actually wants a child's value, with an explicit context it controls. Never evaluated automatically -- that's the whole point: a special form like if or quote decides whether and when to call eval at all, which is exactly what lets an untaken if branch, or quote's own argument, go unevaluated (and unbound-symbol/nonterminating errors inside them stay latent) instead of always eagerly running.

position is this capture's index among its siblings in the enclosing rule's own raw_captures/0 list (its first-occurrence RHS position, for a name captured more than once) -- Ichor.Actions.eval_all/2 sorts by it instead of trusting a plain map's own iteration order, which Elixir/Erlang make no cross-version guarantee about. Defaults to 0, which is only meaningful (and only ever ties) for a %Capture{} built by hand rather than by Ichor.Actions.dispatch_rule/5's own pipeline -- ties fall back to whatever order the underlying map happens to enumerate in, same as before this field existed.