Only if your static types for strings include a seperate type per encoding. Most languages including the ducktyped just use a single encoding internally "utf-8" for example. So the String type is always compatible. For Ruby though it sounds like the string type could be any encoding. That to me sounds dangerous. It's not caused by the language being ducktyped. It's caused by the language having the same type with multiple behaviours. Ruby made strings into a mine field for 99% of programmers and safer for 10%

Not sure that's a good ratio.