tools/go/analysis/passes/composite: fix test fail because flag.Flag new field

For golang/go#65675

Change-Id: I7f609d23e058e54991d657dd9e92f5095f3c7d8f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/804080
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
diff --git a/go/analysis/passes/composite/testdata/src/a/a.go b/go/analysis/passes/composite/testdata/src/a/a.go
index cd69d39..b401134 100644
--- a/go/analysis/passes/composite/testdata/src/a/a.go
+++ b/go/analysis/passes/composite/testdata/src/a/a.go
@@ -7,12 +7,13 @@
 package a
 
 import (
-	"flag"
 	"go/scanner"
 	"go/token"
 	"image"
 	"sync"
 	"unicode"
+
+	"./flag"
 )
 
 var Okay1 = []string{
diff --git a/go/analysis/passes/composite/testdata/src/a/a.go.golden b/go/analysis/passes/composite/testdata/src/a/a.go.golden
index fe73a2e..8498814 100644
--- a/go/analysis/passes/composite/testdata/src/a/a.go.golden
+++ b/go/analysis/passes/composite/testdata/src/a/a.go.golden
@@ -7,12 +7,13 @@
 package a
 
 import (
-	"flag"
 	"go/scanner"
 	"go/token"
 	"image"
 	"sync"
 	"unicode"
+
+	"./flag"
 )
 
 var Okay1 = []string{
diff --git a/go/analysis/passes/composite/testdata/src/a/flag/flag.go b/go/analysis/passes/composite/testdata/src/a/flag/flag.go
new file mode 100644
index 0000000..8159fd8
--- /dev/null
+++ b/go/analysis/passes/composite/testdata/src/a/flag/flag.go
@@ -0,0 +1,12 @@
+// Copyright 2026 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package flag
+
+type Flag struct {
+	Name     string // name as it appears on command line
+	Usage    string // help message
+	Value    any    // value as set
+	DefValue string // default value (as text); for usage message
+}