}
	case *ast.StructType:
		changed := false
		fields := *t.Fields
		fields.List = nil
		for _, f := range t.Fields.List {
			ft := p.rewriteUnsafe(f.Type)
			if ft == f.Type {
				fields.List = append(fields.List, f)
			} else {
				fn := *f
				fn.Type = ft
				fields.List = append(fields.List, &fn)
				changed = true
			}
		}
		if changed {
			r := *t
			r.Fields = &fields

		a := Fields(b)

		// Appending to the results should not change future results.
		var x []byte
		for _, v := range a {
			x = append(v, 'z')
		}

		result := sliceOfString(a)
		if !eq(result, tt.a) {
			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
			continue
		}

		if string(b) != tt.s {
			t.Errorf("slice changed to %s; want %s", string(b), tt.s)
		}
		if len(tt.a) > 0 {