/** Internal boundary validation and option merging shared by public APIs. */
/**
 * Merges caller options over defaults, skipping keys explicitly set to `undefined`.
 *
 * A plain `{ ...defaults, ...options }` lets `{ zoom: undefined }` overwrite the
 * default with `undefined`, which then fails validation. React props, optional
 * chaining and conditional spreads produce that shape constantly, so every
 * defaults merge on a public constructor goes through here.
 */
export declare function mergeOptions<TDefaults extends object, TOptions extends object>(defaults: TDefaults, options: TOptions | undefined): TDefaults & TOptions;
export declare function nonNegativeFinite(value: number, name: string): number;
export declare function rejectLegacyUnit(options: object, oldName: string, replacement: string): void;
/**
 * Fail on a removed option name. An unknown key in an options bag is silently ignored by
 * JavaScript, so a rename would otherwise change behaviour without a word.
 */
export declare function rejectRemovedOption(options: object, oldName: string, replacement: string): void;
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