fix(types): ensure Chai declaration merge works with TS-Go

[LukeAbby]

Description

Context: Currently TypeScript accepts code like this:

interface Foo {
    foo(x: any): void;
    foo: (x: any) => void;
}

While it does not accept code like this:

interface Foo {
    foo: (x: any) => void;
    foo(x: any): void;
}

The only difference being the ordering.

By comparison, in TypeScript Go neither of these are accepted. See microsoft/typescript-go#1192 (comment) for official confirmation by Anders Hejlsberg (lead architect of TypeScript). I noticed this effected Vitest due to its merge of Chai.Assert.containSubset as a callback instead of as a method, leading to a conflict with @types/chai.

No associated issue because it's a small types-only fix.

Please don't delete this checklist! Before submitting the PR, please make sure you do the following:

• It's really useful if your PR references an issue where it is discussed ahead of time. If the feature is substantial or introduces breaking changes without a discussion, PR might be closed.
• Ideally, include a test that fails without this PR but passes with it.
• Please, don't make changes to pnpm-lock.yaml unless you introduce a new test example.

Tests

• Run the tests with pnpm test:ci.

Changesets

• Changes in changelog are generated from PR name. Please, make sure that it explains your changes in an understandable manner. Please, prefix changeset messages with feat:, fix:, perf:, docs:, or chore:.

[netlify]

✅ Deploy Preview for vitest-dev ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	c0a2a03
🔍 Latest deploy log	https://app.netlify.com/projects/vitest-dev/deploys/68541c9d717bf20008482608
😎 Deploy Preview	https://deploy-preview-8188--vitest-dev.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[LukeAbby]

This change is not critically necessary for supporting TS-Go. However while touching this area of the code I noticed that @types/chai does this:

        interface ContainSubset {
            (expected: any): Assertion;
        }

        interface Assertion extends LanguageChains, NumericComparison, TypeComparison {
            ...
            containSubset: ContainSubset;
            ...
        }

And this change makes the polyfill here more compliant with what @types/chai is doing. Currently if someone changed ContainSubset it would break vitest.

[LukeAbby]

This is the change that's critical for TS-Go. You can test this locally by running these commands in packages/vitest:

pnpm add -D @typescript/native-preview
pnpm exec tsgo

Before this change you would get these errors:

src/types/global.ts:20:7 - error TS2300: Duplicate identifier 'containSubset'.

20       containSubset: (val: any, exp: any, msg?: string) => void
         ~~~~~~~~~~~~~

  ../../node_modules/.pnpm/@[email protected]/node_modules/@types/chai/index.d.ts:538:13 - 'containSubset' was also declared here.
    538             containSubset(val: any, exp: any, msg?: string): void;

After, these errors go away.

[LukeAbby]

Could I get a rerun on "Browsers: node-20, macos-latest" and "Build&Test: node-20, windows-latest"?
The macos error is:

Error: Command failed: "/Applications/Firefox.app/Contents/MacOS/Firefox" --version

The windows error is:

@vitest/test-coverage : test test\coverage-test
  test/coverage-test test$ vitest --workspace=vitest.workspace.custom.ts
   ELIFECYCLE  Command failed with exit code 134.

I don't see how either of these could be caused by this change and I see these checks failing elsewhere.

[sheremet-va]

LGTM!