[Bug]: spyOn type definition doesn't work with index signatures

[Maxim-Mazurok]

Version

28.1.1

Steps to reproduce

1. Add this into your test file:

type DoesNotWork = {
  [index: string]: {
    [x: string]: any;
  };

  methodOne: () => void;
  methodTwo: () => void;
};

const doesNotWork = {} as DoesNotWork;

jest.spyOn(doesNotWork, "methodOne"); // error: No overload matches this call

2. Observe an error: No overload matches this call

Expected behavior

I expect it to work as well as in this case:

type Works = {
  methodOne: () => void;
  methodTwo: () => void;
};

const works = {} as Works;

jest.spyOn(works, "methodOne"); // no error

Actual behavior

error: No overload matches this call

Additional context

The problem is in FunctionPropertyNames utility type, it doesn't work as expected in this case.

type Testing = {
  [index: string]: {
    [x: string]: any;
  };

  methodOne: () => void;
  methodTwo: () => void;
};

type FunctionProperties<T> = {
  [K in keyof T]: T[K] extends (...args: any[]) => any ? K : never;
};

/**
 * {
 *   [x: string]: never;
 *   methodOne: "methodOne";
 *   methodTwo: "methodTwo";
 * }
 */
type functionProperties = FunctionProperties<Testing>;

// never
type values = functionProperties[keyof functionProperties];

My real-life use-case is to do this:

import { google } from "googleapis";
jest.spyOn(google, "sheets");

getting

No overload matches this call.
  Overload 1 of 3, '(object: GoogleApis, method: never): never', gave the following error.
    Argument of type 'string' is not assignable to parameter of type 'never'.
  Overload 2 of 3, '(object: GoogleApis, method: never): never', gave the following error.
    Argument of type 'string' is not assignable to parameter of type 'never'.ts(2769)

Environment

System:
    OS: Windows 10 10.0.22000
    CPU: (12) x64 AMD Ryzen 5 3600 6-Core Processor
  Binaries:
    Node: 17.2.0 - ~\AppData\Local\nvs\node\17.2.0\x64\node.EXE
    npm: 8.1.4 - ~\AppData\Local\nvs\node\17.2.0\x64\npm.CMD
  npmPackages:
    jest: ^28.1.1 => 28.1.1

[Maxim-Mazurok]

Fixed by DefinitelyTyped/DefinitelyTyped#60971

[github-actions]

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