Document Poisoning in LazyCell and LazyLock

[connortsui20]

Currently, there is no documentation of poisoning behavior in either LazyCell or LazyLock, even though both of them can be observed as poisoned by users.

LazyCell plagyround example

LazyLock playground example

Open Questions

• Is it worth making the implementation of LazyLock more complicated to ensure that the the panic message is "LazyLock instance has previously been poisoned" instead of "Once instance has previously been poisoned"? See the LazyLock playground link above for more context.
• Does it make sense to move LazyLock into the poison module? It is certainly a poison-able type, but at the same time it is slightly different from the 4 other types currently in the poison module in that it is unrecoverable. I think this is more of a libs-api question.

@rustbot label +T-libs-api

Please let me know if these open questions deserve a separate issue / PR!

[rustbot]

r? @thomcc

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[connortsui20]

Actually r? @Amanieu since you recently reviewed the poisoning documentation PR #144185?

[Amanieu]

• Is it worth making the implementation of LazyLock more complicated to ensure that the the panic message is "LazyLock instance has previously been poisoned" instead of "Once instance has previously been poisoned"? See the LazyLock playground link above for more context.

I think this is valid since Once is an internal implementation detail of LazyLock: users seeing this panic message will be confused since they don't use Once directly in their code. However this can be done in a separate PR.

• Does it make sense to move LazyLock into the poison module? It is certainly a poison-able type, but at the same time it is slightly different from the 4 other types currently in the poison module in that it is unrecoverable. I think this is more of a libs-api question.

This should probably be raised as an open question in #134646, which tracks the poison module.

[Amanieu]

@bors r+ rollup

[bors]

📌 Commit 96adb7d has been approved by Amanieu

It is now in the queue for this repository.