import { If, Not } from "../boolean";
import { Equals } from "../type";
/**
 * gets the readonly keys of `T`
 * does not capture index signatures.
 *
 * @since 0.0.2
 *
 * @example
 * type e0 = ReadonlyKeys<{}> // never
 * type e1 = ReadonlyKeys<{ readonly a: 0 }> // "a"
 * type e2 = ReadonlyKeys<{ readonly a: 0, b?: 1 | undefined, readonly c?: 2 }> // "a" | "c"
 */
export type ReadonlyKeys<T> = {
    [K in keyof T]-?: If<Not<Equals<{
        [P in K]: T[P];
    }, {
        -readonly [P in K]: T[P];
    }>>, K>;
}[keyof T];
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