[tools] go/analysis/passes/modernize: preserve timer calls on unrelated benchmarks

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shuang cui (Gerrit)

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Aug 11, 2026, 11:24:28 PM (4 hours ago) Aug 11

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shuang cui has uploaded the change for review

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go/analysis/passes/modernize: preserve timer calls on unrelated benchmarks

The bloop analyzer removed preceding timer calls based only on the called
testing.B method. As a result, it could remove StartTimer, StopTimer, or
ResetTimer calls made on a different *testing.B value.

Only remove ordinary timer method calls when their receiver matches the
receiver of the b.N loop. Conservatively preserve method expressions.

Add regression tests for unrelated receivers and method expressions.

Fixes golang/go#80841

Change-Id: Iba36ab43415739c3d30bff16de31d56eaee7f2f5

Change diff

diff --git a/go/analysis/passes/modernize/bloop.go b/go/analysis/passes/modernize/bloop.go
index d44c856..c060788 100644
--- a/go/analysis/passes/modernize/bloop.go
+++ b/go/analysis/passes/modernize/bloop.go
@@ -72,7 +72,8 @@
 			}
 			if call, ok := stmt.X.(*ast.CallExpr); ok {
 				obj := typeutil.Callee(info, call)
-				if typesinternal.IsMethodNamed(obj, "testing", "B", "StopTimer", "StartTimer", "ResetTimer") {
+				if typesinternal.IsMethodNamed(obj, "testing", "B", "StopTimer", "StartTimer", "ResetTimer") &&
+					timerCallReceiverIs(call, b) {
 					// Delete call statement.
 					// TODO(adonovan): delete following newline, or
 					// up to start of next stmt? (May delete a comment.)
@@ -160,6 +161,14 @@
 	return nil, nil
 }
 
+// timerCallReceiverIs reports whether call is an ordinary method call whose
+// receiver is syntactically equal to want. Method expressions such as
+// (*testing.B).ResetTimer(b) are conservatively ignored.
+func timerCallReceiverIs(call *ast.CallExpr, want ast.Expr) bool {
+	sel, ok := ast.Unparen(call.Fun).(*ast.SelectorExpr)
+	return ok && astutil.EqualSyntax(sel.X, want)
+}
+
 // uses reports whether the subtree cur contains a use of obj.
 func uses(index *typeindex.Index, cur inspector.Cursor, obj types.Object) bool {
 	for use := range index.Uses(obj) {
diff --git a/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go b/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go
index 33ffd77..f55b096 100644
--- a/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go
+++ b/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go
@@ -15,6 +15,24 @@
 	}
 }
 
+var otherBenchmark *testing.B
+
+func BenchmarkOtherReceiver(b *testing.B) {
+	other := new(testing.B)
+	other.ResetTimer() // not deleted: receiver is not b
+	otherBenchmark = other
+
+	for range b.N { // want "b.N can be modernized using b.Loop.."
+	}
+}
+
+func BenchmarkMethodExpression(b *testing.B) {
+	(*testing.B).ResetTimer(b) // conservatively not deleted
+
+	for range b.N { // want "b.N can be modernized using b.Loop.."
+	}
+}
+
 func BenchmarkB(b *testing.B) {
 	// setup
 	{
diff --git a/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go.golden b/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go.golden
index a2def76..0f7b411 100644
--- a/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go.golden
+++ b/go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go.golden
@@ -14,6 +14,24 @@
 	}
 }
 
+var otherBenchmark *testing.B
+
+func BenchmarkOtherReceiver(b *testing.B) {
+	other := new(testing.B)
+	other.ResetTimer() // not deleted: receiver is not b
+	otherBenchmark = other
+
+	for b.Loop() { // want "b.N can be modernized using b.Loop.."
+	}
+}
+
+func BenchmarkMethodExpression(b *testing.B) {
+	(*testing.B).ResetTimer(b) // conservatively not deleted
+
+	for b.Loop() { // want "b.N can be modernized using b.Loop.."
+	}
+}
+
 func BenchmarkB(b *testing.B) {
 	// setup
 	{

Change information

Files:

M go/analysis/passes/modernize/bloop.go
M go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go
M go/analysis/passes/modernize/testdata/src/bloop/bloop_test.go.golden

Change size: S

Delta: 3 files changed, 46 insertions(+), 1 deletion(-)

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shuang cui (Gerrit)

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Aug 11, 2026, 11:25:08 PM (4 hours ago) Aug 11

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shuang cui voted Commit-Queue+1

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