fix(instrument): SelectorExpr in IncDecStmt now instrumented (#30)

[kolkov]

Summary

Fixes #30: s.x++ was not being instrumented because shouldInstrument() skips all SelectorExpr to avoid method calls/package functions.

Root cause: In visitSelectorInModifyContext(), we recorded Node: expr (SelectorExpr), but findParentStatement() then returned the outermost containing statement (BlockStmt) instead of the IncDecStmt. This caused the instrumentation lookup to fail during code generation.

Solution: Pass the parent statement (IncDecStmt) to visitSelectorInModifyContext() and use it as Node. This ensures findParentStatement() returns the correct statement for insertion.

Changes

• Modified visitSelectorInModifyContext(parentStmt, expr) to accept parent statement
• Use parentStmt as Node so findParentStatement() returns correct statement
• Added TestInstrumentFile_SelectorExprIncDec test case
• Added TestInstrumentFile_SelectorExprInGoroutine for full reproduction
• Updated CHANGELOG.md for v0.8.3

Before/After

Before fix:

func update(s *S) {
    s.x++  // No race detection!
}

After fix:

func update(s *S) {
    race.RaceRead(uintptr(unsafe.Pointer(&s.x)))
    race.RaceWrite(uintptr(unsafe.Pointer(&s.x)))
    s.x++
}

Test plan

• TestInstrumentFile_SelectorExprIncDec passes
• TestInstrumentFile_SelectorExprInGoroutine passes
• All existing tests pass
• pre-release-check.sh passes with 0 errors
• Coverage: 85.7%

Acknowledgments

Thanks to @thepudds for finding this critical bug in Issue #27 comments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.67%. Comparing base (d8f3aba) to head (76a746e).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #31      +/-   ##
==========================================
+ Coverage   69.45%   69.67%   +0.22%     
==========================================
  Files          28       28              
  Lines        2933     2955      +22     
==========================================
+ Hits         2037     2059      +22     
  Misses        777      777              
  Partials      119      119              

Flag	Coverage Δ
unittests	69.67% <100.00%> (+0.22%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
cmd/racedetector/instrument/visitor.go	74.47% <100.00%> (+1.24%)	⬆️

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