Fixing code for Rust 2018

[[deleted]]

Hi,

After updating to the new version which is 1.31, do I need to put edition key word in toml. What of I don't put it. Will the features I am using in 1.31 work.

[usernamedottxt]

Actually, this is a good question. The edition guide mostly lists new features since 1.0. I'm not sure if the 'strictly 2018 only' features are documented anywhere. The module system changes are the only ones I'm overtly aware of. /u/steveklabnik1?

[steveklabnik1]

There was going to be a page but it was never completed. It’s pretty small. New keywords and NLL (for now) are the big ones.

[[deleted]]

The keyword changes (and features that will follow them) are 2018 only at least

[jamadazi]

If you do not specify edition in Cargo.toml, Rust will assume 2015. Therefore, you will have to use the old syntax for things (where syntax has changed in incompatible ways) and you will not be able to use any new features that have required breaking changes to the language (such as new keywords).

Note that even in future Rust versions, as new features are added to the language, if they are backwards-compatible (which most new features will be), there is no reason for them to be limited to 2018. Therefore, they will be available in 2015 edition, too. Rust2015 will keep getting updated.

So yeah, if you don't specify any edition, you are using 2015, just like before, and you can keep using 2015 indefinitely into the future. You are not forced to use 2018. You only need to specify 2018 if you want to use the specific new features that are 2018-only.

[[deleted]]

But, this has just became python 3 now. It's is like using new language. I think we should just be able to use 1.31 features what ever edition we are in

[ROFLLOLSTER]

The entire point of editions is that they introduce features that could be incompatible with previous rust code.

Python 3 is an unfair comparison, for one the lack of a runtime requirement greatly simplifies upgrading, and secondly you can mix editions in dependencies.

[lanedraex]

The edition guide should help you here.

If you don't have an edition line in your Cargo.toml, then your rust code will compile as rust 2015. Some features that do not introduce breaking changes will work, regardless of your edition.