/**
 * How a `validation.pattern` is enforced on the rendered input.
 *
 * Browsers compile the `pattern` attribute as `^(?:pattern)$` with the `v`
 * flag and silently ignore it when that fails, which would drop the constraint
 * altogether. Patterns that are valid `v`-mode regexes are left to the browser
 * (`patternMismatch`); anything else that still compiles as a plain JS regex is
 * matched by the component and reported through `setCustomValidity`.
 */
export type CompiledPattern = {
    mode: "native";
} | {
    mode: "custom";
    regex: RegExp;
};
export declare function compilePattern(pattern: string | null | undefined): CompiledPattern | null;