I definitely had to add type annotations when compiling "old" Rust code with a modern version, but it wasn't a huge deal in practice. While Rust's handling of

I definitely had to add type annotations when compiling "old" Rust code with a modern version, but it wasn't a huge deal in practice. While Rust's handling of backcompat isn't perfect, I think it's very good given how young and fast-moving the language is. I usually have more trouble dealing with old C++ code on newer versions of G++/LLVM than Rust. Admittedly that C++ code often predates the very existence of Rust, but still, you'd expect a higher standard of backward-compatibility from such an old and widespread language.