/**
 * Collection-Op Recognition Helpers
 *
 * In @rcrsr/rill 0.19.0 the dedicated AST nodes for `each`, `map`, `fold`,
 * `filter` were removed; collection operators now parse as ordinary HostCall
 * nodes (in pipe-target position) whose `name` is one of the five callable
 * builtins below.
 *
 * | Old keyword              | New callable | Behaviour                       |
 * | ------------------------ | ------------ | ------------------------------- |
 * | `each { body }`          | `seq`        | sequential, no accumulator      |
 * | `each(init) { body }`    | `acc`        | sequential scan with accumulator|
 * | `map { body }`           | `fan`        | parallel                        |
 * | `fold(init) { body }`    | `fold`       | sequential reduction            |
 * | `filter { body }`        | `filter`     | parallel predicate              |
 *
 * The closure argument may parse as either:
 *   - a bare-block form: `seq({ body })` — primary is a BlockNode, or
 *   - an explicit closure: `seq(|x|(body))` — primary is a ClosureNode.
 */
import type { ASTNode, HostCallNode, ClosureNode, BlockNode } from '@rcrsr/rill';
export declare const COLLECTION_OP_NAMES: Set<"filter" | "seq" | "fan" | "fold" | "acc">;
export type CollectionOpName = 'seq' | 'fan' | 'fold' | 'filter' | 'acc';
/** True when the node is a HostCall to one of the five collection callables. */
export declare function isCollectionOpCall(node: ASTNode): node is HostCallNode & {
    name: CollectionOpName;
};
/** True for callables that execute the closure in parallel (`fan`, `filter`). */
export declare function isParallelOp(name: CollectionOpName): boolean;
/** True for callables that thread an accumulator (`fold`, `acc`). */
export declare function isAccumulatorOp(name: CollectionOpName): boolean;
/**
 * Resolve the body argument of a collection-op call.
 *
 * Each arg is wrapped in a `PipeChain` whose head is a `PostfixExpr` whose
 * primary is the actual value. We scan args left-to-right and return the
 * first whose primary is a `Closure` or `Block`. Returns null when no such
 * arg exists (e.g. `seq($fn)` where the arg is a Variable).
 */
export declare function getCollectionOpBody(node: HostCallNode): ClosureNode | BlockNode | null;