b.RunParallel(func(pb *testing.PB) {
		var s struct{}
		for pb.Next() {
			if err := Unmarshal(j, &s); err != nil {
				b.Fatalf("Unmarshal error: %v", err)
			}
		}
	})
}

func BenchmarkTypeFieldsCache(b *testing.B) {
	b.ReportAllocs()
	var maxTypes int = 1e6
	if testenv.Builder() != "" {
		maxTypes = 1e3 // restrict cache sizes on builders
	}

	// Dynamically generate many new types.