Canary: `MergeDeep` failures in `typescript@next` not detected by canary tests about type-fest

[jakebailey]

FWIW you can pretty easily bisect this using every-ts: https://www.npmjs.com/package/every-ts

$ every-ts fetch
$ every-ts bisect bad 5.4.0-dev.20231121
$ every-ts bisect good 5.4.0-dev.20231119
$ every-ts tsc
$ every-ts bisect bad
$ every-ts tsc
$ every-ts bisect good
...

[voxpelli]

The regression should be caused by any of the following commits: microsoft/TypeScript@b4aefd2...13c9b16

Rather, as [email protected] seems to pass as well: microsoft/TypeScript@ffc21e5...13c9b16

[voxpelli]

Suggested to add type-fest into typescript's own canary tests: microsoft/typescript-error-deltas#129

[voxpelli]

Finally got time to look into this and every-ts is really really great @jakebailey!

Came to the conclusion that its microsoft/TypeScript#56004 that caused these errors