cmd/vet: warn on 3-clause loops where an iterator variable contains a lock type when GoVersion>=1.22
timothy-king opened this issue · 10 comments
Proposal Details
Extend the copylock analyzer to emit a warning on the copy of the loop variable between iterations that occurs immediately before the loop's Post statement in Go >= 1.22. The requirements for the warning are when:
- a 3-clause for loop declares a loop scoped variable containing a lock type,
- the file's GoVersion is >= 1.22,
- the name of the variable is not
_, and - the Init statement of the for loop is not otherwise reported.
Example:
for _, mu := 0, (sync.Mutex{}); x < 10; x++ { // want "for loop iteration copies lock value to mu: sync.Mutex"
_ = mu.TryLock()
}
Relevant part of the spec https://go.dev/ref/spec#For_clause :
The variable used by each subsequent iteration is declared implicitly before executing the post statement and initialized to the value of the previous iteration's variable at that moment.
Proposed implementation http://go.dev/cl/569955.
Related #66156. This is 'Case 1'.
Change https://go.dev/cl/569955 mentions this issue: go/analysis/passes/copylock: add support for ForStmt
This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group
This proposal has been added to the active column of the proposals project
and will now be reviewed at the weekly proposal review meetings.
— rsc for the proposal review group
Based on the discussion above, this proposal seems like a likely accept.
— rsc for the proposal review group
The proposal details are in #66387 (comment).
No change in consensus, so accepted. 🎉
This issue now tracks the work of implementing the proposal.
— rsc for the proposal review group
The proposal details are in #66387 (comment).
Will this be merged to the main repo some day?
This is expected to go into tip during the next x/tools. Probably not more than a month. The first release it is expected to go into is 1.24.
This vet change seems like something that needs to be mentioned in Go 1.24 release notes, and it's not mentioned there yet. Reopening as a release blocker to track that.
Change https://go.dev/cl/632315 mentions this issue: doc/next: document copylock changes