fix: 一旦変数に入るケースをカバー

testdata/src/a/define.go

@@ -6,7 +6,7 @@ import (
 
 type a struct {
 	ct  ct
-	ict interface{ Err(context.Context) error }
+	ict ict
 }
 
 func g() error {
@@ -51,5 +51,6 @@ func (r) r(context.Context) []*ct {
 
 type ict interface {
 	Err(context.Context) error
+	Result() (struct{}, error)
 }
 type mmu []ict

testdata/src/a/struct-field.go

@@ -75,4 +75,11 @@ func (a *a) A(ctx context.Context) {
 	if err := a.ict.Err(ctx); err != nil {
 		_ = fmt.Errorf("a.ict.Err: %w", err)
 	}
+	_, err := a.ict.Result()
+	if err != nil {
+		_ = fmt.Errorf("hoge: %w", err) // want `the error-wrapping message should be "a\.ict\.Result: %w"`
+	}
+	if err != nil {
+		_ = fmt.Errorf("a.ict.Result: %w", err)
+	}
 }

testdata/src/a/struct-field.go.golden

@@ -75,4 +75,11 @@ func (a *a) A(ctx context.Context) {
 	if err := a.ict.Err(ctx); err != nil {
 		_ = fmt.Errorf("a.ict.Err: %w", err)
 	}
+	_, err := a.ict.Result()
+	if err != nil {
+		_ = fmt.Errorf("a.ict.Result: %w", err) // want `the error-wrapping message should be "a\.ict\.Result: %w"`
+	}
+	if err != nil {
+		_ = fmt.Errorf("a.ict.Result: %w", err)
+	}
 }

walk.go

@@ -63,6 +63,8 @@ func (w *walker) walk(ctx context.Context, depth int, v poser) ([]string, bool)
 		return w.walkOperands(ctx, depth+1, v)
 	case *ssa.ChangeInterface:
 		return w.walkOperands(ctx, depth+1, v)
+	case *ssa.Extract:
+		return w.walkOperands(ctx, depth+1, v)
 	case *ssa.Call:
 		return formatCall(ctx, v)
 	}