hardhat/src/types/utils.ts

Hardhat is an extensible developer tool that helps smart contract developers increase productivity by reliably bringing together the tools they want.

/**
 * All the parameters except the first one.
 */
export type ParametersExceptFirst<T> = T extends (
  ...args: [any, ...infer P]
) => any
  ? P
  : never;

/**
 * All the parameters of a function, except the last one.
 */
export type ParametersExceptLast<T> = T extends (
  ...args: [...infer P, any]
) => any
  ? P
  : never;

/**
 * All the parameters of a function, except the first and last ones.
 */
export type ParametersExceptFirstAndLast<T> = T extends (
  ...args: [any, ...infer P, any]
) => any
  ? P
  : never;

/**
 * The last parameter of a function.
 */
export type LastParameter<T> = T extends (
  ...args: [...infer _P, infer Last]
) => any
  ? Last
  : never;

/**
 * The parameters of a function.
 */
export type Params<T> = T extends (...args: infer P) => any ? P : never;

/**
 * The return type of a function.
 */
export type Return<T> = T extends (...args: any[]) => infer Ret ? Ret : never;

/**
 * The same type as T, but with the specified keys required.
 */
export type RequireField<T, K extends keyof T> = T & {
  [P in K]-?: T[P];
};

/**
 * A result that can either have a value or an error.
 */
export type Result<ValueT, ErrorT> =
  | { readonly success: true; readonly value: ValueT }
  | { readonly success: false; readonly error: ErrorT };

/**
 * Returns the keys of T tht don't map to never.
 */
export type NonNeverKeys<T> = {
  [K in keyof T]: T[K] extends never ? never : K;
}[keyof T];