/**
 * `assign` runtime semantics — reassignment of an existing mutable binding.
 *
 * Operational semantics:
 *   1. Resolve the existing binding named by `target` in the current
 *      environment (it MUST already exist — implicit declaration-by-assign
 *      diverges: Python auto-creates a local, strict TS rejects it).
 *   2. Evaluate the RHS exactly once over the shared portable-scalar domain.
 *   3. Apply the operator in place (`=` stores the RHS; `+=` adds numbers or
 *      concatenates strings) and emit one observable trace event
 *      `{op:"assign", target, value}` carrying the *new* value.
 *   4. Complete normally.
 *
 * Portability domain:
 *   - `target` is a simple, non-reserved identifier already bound to a number,
 *     string, or boolean. (A null/undefined-typed binding can't be portably
 *     reassigned — TS infers a narrow type that rejects the new value.)
 *   - `op` is `=` or `+=` only. Plain `=` MUST preserve the binding's type;
 *     `+=` requires both operands to be numbers (add) or both strings (concat).
 *   - The RHS is a portable scalar expression (see `./portable-scalar.ts`).
 *
 * Exclusions (out of domain — must fail preconditions):
 *   Implicit declaration via assign; assigning an undeclared name; `const`
 *   reassignment (rejected at emit time, not reachable here); cross-type
 *   reassignment (`number = "x"`); cross-type compound (`number += "x"`);
 *   postfix `++`/`--` and compound ops other than `+=`; destructuring,
 *   property, and index targets.
 */
import { type NodeContract } from './index.js';
export declare const assignContract: NodeContract;
/** Idempotent registration. Test cleanup that clears the registry must re-call. */
export declare function registerAssignContract(): void;
/** Reset registration flag — only for test cleanup that clears the registry. */
export declare function _resetAssignContractForTest(): void;