Expect calls custom `inspect()` function unexpectedly

Describe the bug

Any object that has an inspect() function will be called when passed to expect(). If this function happens to expect an argument, for example inspect(fn: () => void) then the test will fail for the wrong reason. This doesn't seem to mentioned in the api and means you need to guard around this currently by doing more targeted tests.

Reproduction

Using vitest@^0.34.0 (including beta 1.0.0 releases) the following test:

class Example {
  public inspect(fn: () => void) {
    fn();
  }
}

it('custom inspect function', (): void => {
  expect(
    new Example(),
  ).toStrictEqual(undefined);
});

Will output as expected:

 FAIL  src/example.test.ts > custom inspect function
TypeError: fn is not a function
 ❯ Example.inspect src/event/service/foo.test.ts:3:5
      1| class Example {
      2|   public inspect(fn: () => void) {
      3|     fn();
       |     ^
      4|   }
      5| }
 ❯ inspectCustom node_modules/loupe/loupe.js:793:20
 ❯ Object.inspect node_modules/loupe/loupe.js:827:20

This appears to be down to loupe but again, this is unexpected.

System Info

System:
    OS: macOS 14.0
    CPU: (12) arm64 Apple M2 Max
    Memory: 2.27 GB / 64.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 18.18.1 - ~/.nvm/versions/node/v18.18.1/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v18.18.1/bin/yarn
    npm: 10.2.0 - ~/.nvm/versions/node/v18.18.1/bin/npm
    pnpm: 8.9.0 - ~/.nvm/versions/node/v18.18.1/bin/pnpm
  Browsers:
    Chrome: 119.0.6045.123
    Safari: 17.0
  npmPackages:
    @vitest/coverage-v8: ^0.34.5 => 0.34.6 
    vitest: ^0.34.5 => 0.34.6

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

Start with the expect formatting path and the loupe/loupe.js stack entries shown in the reproduction. Add a regression test for an object whose inspect function requires an argument, then run the relevant expect tests and confirm that passing the object does not invoke that function or produce the unrelated TypeError.