vitest 0.31.0 breaks vi.fn

[bc-m]

Describe the bug

Using vi.fn in vi.mock not working anymore after upgrading to vitest 0.31.0. The function with vi.fn returns only undefined, ignoring the own implementation.

I have attached two Stackblitz examples with two test files, one with vi.fn', the other without. You will see that on v0.30.0 both variants work, after upgrading to v0.31.0 only the one without vi.fn` works.

Reproduction

• Stackblitz with vitest@0.30.0: https://stackblitz.com/edit/node-ltocvc
• Stackblitz with vitest@0.31.0: https://stackblitz.com/edit/node-fsagxk

System Info

From stackblitz:
  System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 16.14.2 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 7.17.0 - /usr/local/bin/npm
  npmPackages:
    vite: 4.3.5 => 4.3.5 
    vitest: ^0.31.0 => 0.31.0

Used Package Manager

npm

Validations

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• Read the Contributing Guidelines.
• Read the docs.
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• The provided reproduction is a minimal reproducible example of the bug.

[stackblitz]

Start a new pull request in StackBlitz Codeflow.

• node-ltocvc (Open reproduction)
• node-fsagxk (Open reproduction)

[sheremet-va]

Stackblitz doesn't even call vi.mock, but locally it works 🤔

This issue is probably a duplicate of #3335