cargo fix --clippy isn't as smart as I want it to be :(

[jyn514]

This gives a warning instead of replacing it with the suggested code:

$ cargo +nightly fix -Z unstable-options --clippy
warning: using `clone` on a `Copy` type
   --> src/parse/mod.rs:258:27
    |
258 |                 location: self.next_location().clone(),
    |                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try dereferencing it: `*self.next_location()`

It would be really nice to have this be done automatically, since I currently have about 20 of these warnings in my code.

$ cargo +nightly --version
cargo 1.40.0-nightly (5da4b4d47 2019-10-28)
$ ~/.rustup/toolchains/nightly-x86_64-apple-darwin/bin/rustfmt --version
rustfmt 1.4.9-nightly (33e36670 2019-10-07)

[ehuss]

Thanks for the report. I think there are two things here:

1. The clone_on_copy lint has an Applicability of Unspecified. cargo fix will only apply MachineApplicable lints. You may want to file an issue on the clippy repo to figure out why it is Unspecified. It looks like there is at least one issue (False positive for clone_on_copy when the clone is immediately borrowed rust-clippy#1472) where it gives false positives.
2. A workaround would be cargo fix: Automatically try applying non-MachineApplicable suggestions cargo#13023, where an opt-in could be added to try non-machine-applicable suggestions.

[jyn514]

A workaround would be rust-lang/cargo#13023

So if I set __CARGO_FIX_YOLO then this will automatically fix everything (possible with false positives)? That's great, thanks for letting me know!

[Manishearth]

Yeah, please file an issue on the Clippy repo to improve this suggestion. Clippy suggestions are largely per-case so not all of them exist yet in machine applicable form.