vet: copylock check doesn't detect certain copies

[valyala]

copylock check must emit a warning on copying sync.Mutex or struct containing sync.Mutex. It doesn't detect the following cases:

        var a sync.Mutex
        b := a   // doesn't detect
        var c = a  // doesn't detect
        b = a  // detects

See #8005 for details.

[valyala]

Submitted a patch for code review - https://go-review.googlesource.com/20254 .

[gopherbot]

CL https://golang.org/cl/20254 mentions this issue.

[valyala]

Added yet another patch for detecting locks' copying inside composite literals:

type A struct {
   L sync.Mutex
}

var m sync.Mutex
a := A{
    L: m,   // now this case is detected
}
b := []sync.Mutex{m, a.L}  // and this one
c := map[string]sync.Mutex{"foo": m}  // and this one

[valyala]

https://go-review.googlesource.com/20258

[gopherbot]

CL https://golang.org/cl/20258 mentions this issue.

[josharian]

Thanks for working on these. I left some comments and asked Rob to take over reviewing once they're addressed (that's what R=r means).

[valyala]

@josharain, I updated the CL according to comments.

[josharian]

Please ping the CL. (Just write a comment that says "Ping.") Feel free to repeat as needed. I'm leaving the remainder of the review to Rob.

[valyala]

There is yet another case not covered by cmd/vet:

var a [5]sync.Mutex
b := a // here we copy mutexes by value

Will create a CL for this case.

[valyala]

See the CL

[valyala]

Yet another case has been caught and covered by the CL mentioned above:

a := sync.Mutex{}
a = sync.Mutex{}  // here a is overwritten by new value