track: Migrated the existing exercises to the Rust 2018 edition

[ZapAnton]

This PR shows what simple migration to the 2018 edition would look, when cargo fix is applied to every exercise on the track.

Since the changes were nor discussed nor approved by the maintainers , this PR serves as a demonstration of the migration, and should be closed, if the changes are not desirable.

A script, that was used for the migration:

#!/usr/bin/env bash                                                                                                                               
                                                                                                                                                  
for dir in exercises/*/; do                                                                                                                       
    (                                                                                                                                             
        cd $dir                                                                                                                                   
                                                                                                                                                  
        sed -i '2iedition = "2018"' Cargo.toml                                                                                                    
                                                                                                                                                  
        cargo fix --edition-idioms --allow-dirty                                                                                                  
                                                                                                                                                  
        cargo fmt                                                                                                                                 
                                                                                                                                                  
        cargo clean                                                                                                                               
    )                                                                                                                                             
done    

[petertseng]

I imagine students will appreciate being able to use 2018. I seem to recall there was an example solution I wrote recently where I would have benefited from a non-lexical lifetime.

I would like to see the cargo fmt results in a different commit, because they are not related to moving editions. I'd like to also take this opportunity to remind interested individuals who might have an opinion on #659 .

cargo fix probably can go in the same commit as addition edition however.

[ZapAnton]

Done

[coriolinus]

Approved pending getting Travis to pass. Haven't looked yet into what's causing that failure.

One interesting exercise which I have not yet performed: with a pre-rust-2018 compiler, attempt to independently compile all stubs and examples. I intuit that all stubs should compile, but that several examples will not. However, I assert that it is acceptable to impose a minimum rustc version for this track, given the ease of upgrading with rustup.

[ZapAnton]

The build failed for several reasons:

• The READMEs for some exercises are not up-to-date. Since simple-cipher, two-fer: READMEs from problem-specifications #771 was merge the rebase will solve this.
• Some deprecated exercises (namely nucleotide-codons and hexadecimal) were modified and included in the Travis check. Since they are deprecated and do not even have a stub file, they could be ignored.
• dominoes and reverse-string have some actual errors in them. Will investigate further

[ZapAnton]

Some deprecated exercises (namely nucleotide-codons and hexadecimal) were modified and included in the Travis check.

Actually that raises a question - should deprecated exercises be present on the track? Maybe they could be removed, so not to complicate Travis scripts?

[coriolinus]

Agree that deprecated exercises could be removed.

…

On Mon, Dec 10, 2018 at 11:01 AM Zapolsky Anton ***@***.***> wrote: Some deprecated exercises (namely nucleotide-codons and hexadecimal) were modified and included in the Travis check. Actually that raises a question - should deprecated exercises be present on the track? Maybe they could be removed, so not to complicate Travis scripts? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#769 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AHdeTmTCgcJ1FdytZXla34X87MzOQLh1ks5u3jDjgaJpZM4ZKSjG> .

[ZapAnton]

OK, now Travis has failed only because of the deprecated exercises. To make it pass I would have to rebase against #773

[petertseng]

Note: dfdb48f should be good

[petertseng]

Trying with just the edition and use path changes to see what's required to build

[petertseng]

Okay, that build succeeded, so only the use path changes are required. Will leave notes in commit messages explaining that.

[petertseng]

I decided that the cargo fix does instead go in a separate commit, since I discovered it is not required for compilation

[petertseng]

Other changes I made to support this PR:

• forth: Prepare for 2018 by not using Term and using ? not try! #779
• Add edition to all the Cargo-example.toml as well
• Apply the use crate:: to scale-generator and poker as well, where they were needed. Commit 9dad928