Semantics matter. This is a mistake C++ has made and will probably pay for when it eventually tries to land pattern matching. Rust knows that Option<Goose> and

Semantics matter. This is a mistake C++ has made and will probably pay for when it eventually tries to land pattern matching. Rust knows that Option<Goose> and Result<Goose,()> are completely different semantically, likewise Result<Happy,Sad> and Either<Happy,Sad> communicate quite different intents even if the in-memory representations are identical.