Rename .connect() to .join() in SliceConcatExt.


Rust has a string concatenation method named .connect() in SliceConcatExt. However, this does not align with the precedents in other languages. Most languages use .join() for that purpose, as seen later.

This is probably because, in the ancient Rust, join was a keyword to join a task. However, join retired as a keyword in 2011 with the commit rust-lang/rust@d1857d3. While .connect() is technically correct, the name may not be directly inferred by the users of the mainstream languages. There was a question about this on reddit.

The languages that use the name of join are:

The languages not using join are as follows. Interestingly, they are all functional-ish languages.

Note that Rust also has .concat() in SliceConcatExt, which is a specialized version of .connect() that uses an empty string as a separator.

Another reason is that the term “join” already has similar usage in the standard library. There are std::path::Path::join and std::env::join_paths which are used to join the paths.

Detailed design

While the SliceConcatExt trait is unstable, the .connect() method itself is marked as stable. So we need to:

  1. Deprecate the .connect() method.
  2. Add the .join() method.

Or, if we are to achieve the instability guarantee, we may remove the old method entirely, as it’s still pre-1.0. However, the author considers that this may require even more consensus.


Having a deprecated method in a newborn language is not pretty.

If we do remove the .connect() method, the language becomes pretty again, but it breaks the stability guarantee at the same time.


Keep the status quo. Improving searchability in the docs will help newcomers find the appropriate method.

Unresolved questions

Are there even more clever names for the method? How about .homura(), or .madoka()?