go/types: data race due to lazy interface completion

[findleyr]

Sample failure:

https://build.golang.org/log/66aed38eb7030ee6db09e17179d26ce42d59b316

Lazy interface completion causes data races in x/tools. We need to either make interface completion concurrency-safe, or ensure that all interfaces that escape the Checker have been completed.

CC @griesemer

[griesemer]

Is this because Interface.Complete is not doing anything anymore? That is, would it be sufficient to revert that change? Or is it a bigger problem?

[findleyr]

Is this because Interface.Complete is not doing anything anymore? That is, would it be sufficient to revert that change? Or is it a bigger problem?

Necessary but not sufficient. Here's a failure at the dev.typeparams merge:
https://build.golang.org/log/53e6ff359c770b04ed89035e59f2038b3d87268e

[gopherbot]

Change https://golang.org/cl/342710 mentions this issue: Revert "go/types: make Interface.Complete a no-op"

[gopherbot]

Change https://golang.org/cl/342749 mentions this issue: go/types: check if the interface is already complete in Complete

[findleyr]

I believe this is fixed now, but I'll leave it open for visibility in case there are any additional flakes in the race builders.

Will close tomorrow if no additional failures.

[findleyr]

Closing as the build dashboard looks clean.