import type { VariableType } from "../types.js";
/**
 * Post-order transform of a VariableType tree. `fn` is invoked on each
 * node AFTER its children have been transformed, so children are already
 * in their new form when `fn` sees the parent. Returns a new tree; the
 * input is not mutated.
 *
 * Sibling of `visitTypes` (observer). Every VariableType variant must be
 * enumerated here — adding a new variant means updating both functions.
 *
 * Useful for type substitution, normalization, and any "rewrite this
 * tree" operation. Encapsulates the recursion so callers express the
 * "what" (a single-node transform) without re-walking every variant.
 */
export declare function mapTypes(t: VariableType, fn: (t: VariableType) => VariableType): VariableType;
/**
 * Pre-order walk of every nested VariableType. The visitor is invoked once
 * per node, root first. Returning `true` from the visitor halts the walk
 * and propagates `true` back to the caller (used for short-circuiting
 * "does any nested type satisfy P?" predicates).
 */
export declare function visitTypes(t: VariableType, visit: (t: VariableType) => boolean | void): boolean;