A list literal, [a, b, ?c].
optional_indices lists, in order, the positions of elements written
with ?, which are added only when their optional value is present.
Summary
Types
@type t() :: %CEL.Expr.ListLiteral{ elements: [CEL.Expr.t()], id: CEL.Checked.expr_id(), optional_indices: [non_neg_integer()], type: CEL.Expr.type() }