/**
 * Calculate the specificity of a single CSS selector.
 *
 * @param selector - The CSS selector of interest.
 *
 * @returns The specificity of the selector.
 *
 * #### Undefined Behavior
 * The selector is invalid.
 *
 * #### Notes
 * This is based on https://www.w3.org/TR/css3-selectors/#specificity
 *
 * A larger number represents a more specific selector.
 *
 * The smallest possible specificity is `0`.
 *
 * The result is represented as a hex number `0x<aa><bb><cc>` where
 * each component is the count of the respective selector clause.
 *
 * If the selector contains commas, only the first clause is used.
 *
 * The computed result is cached, so subsequent calculations for the
 * same selector are extremely fast.
 */
export declare function calculateSpecificity(selector: string): number;
/**
 * Test whether a selector is a valid CSS selector.
 *
 * @param selector - The CSS selector of interest.
 *
 * @returns `true` if the selector is valid, `false` otherwise.
 *
 * #### Notes
 * The computed result is cached, so subsequent tests for the same
 * selector are extremely fast.
 */
export declare function isValidSelector(selector: string): boolean;
/**
 * Validate a CSS selector.
 *
 * @param selector - The CSS selector of interest.
 *
 * @returns The provided selector.
 *
 * @throws An error if the selector is invalid.
 */
export declare function validateSelector(selector: string): string;
/**
 * Test whether an element matches a CSS selector.
 *
 * @param elem - The element of interest.
 *
 * @param selector - The valid CSS selector of interest.
 *
 * @returns `true` if the element is a match, `false` otherwise.
 *
 * #### Notes
 * This function uses the builtin browser capabilities when possible,
 * falling back onto a document query otherwise.
 */
export declare function matchesSelector(elem: Element, selector: string): boolean;