encoding/gob: error decoding a slice of pointers to recursive type

[dragos-scio]

What version of Go are you using (go version)?

$ go version
go version go1.15.14 darwin/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

It reproduces in playground too

What did you do?

https://play.golang.org/p/Tjcurb98oUg

What did you expect to see?

Serialize / deserialize correctly.

What did you see instead?

If the first value passed is a list of pointers, it doesn't deserialize

[dragos-scio]

@shivaal-scio noticed this related bug, and how to encode / decode a non pointer version to avoid the issue
#2995 (comment)

[seankhliao]

cc @robpike

seems to be some initialization that works for the non pointer version
slightly shorter repro