"help: remove the extra argument" prints too much of the function arguments

[jyn514]

Given the following code: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=d6dfe3d605639255444883813f8376db

enum CargoMessage {
    CompilerArtifact {
        filenames: Vec<String>,
        target: CargoTarget,
        extra: bool,
    }
}

struct CargoTarget {
    crate_types: Vec<String>,
}

pub fn run_cargo() {
    let is_debug_info = |_| true;
    let is_dylib = |_| true;
    let is_check = true;
    let ok = stream_cargo(vec![], &mut |msg| {
        let (filenames, crate_types) = match msg {
            CargoMessage::CompilerArtifact {
                filenames,
                target: CargoTarget { crate_types },
                ..
            } => (filenames, crate_types),
            _ => return,
        };
        for filename in filenames {
            // Skip files like executables
            if !(filename.ends_with(".rlib")
                || filename.ends_with(".lib")
                || filename.ends_with(".a")
                || is_debug_info(&filename)
                || is_dylib(&filename)
                || (is_check && filename.ends_with(".rmeta")))
            {
                continue;
            }
        }
    });
}

pub fn stream_cargo(
    cb: &mut dyn FnMut(CargoMessage),
) -> bool {
  true
}

The current output is:

error[[E0061]](https://doc.rust-lang.org/stable/error-index.html#E0061): this function takes 1 argument but 2 arguments were supplied
  --> src/lib.rs:17:14
   |
17 |     let ok = stream_cargo(vec![], &mut |msg| {
   |              ^^^^^^^^^^^^ ------ argument of type `Vec<_>` unexpected
   |
note: function defined here
  --> src/lib.rs:41:8
   |
41 | pub fn stream_cargo(
   |        ^^^^^^^^^^^^
42 |     cb: &mut dyn FnMut(CargoMessage),
   |     --------------------------------
help: remove the extra argument
   |
17 ~     let ok = stream_cargo(&mut |msg| {
18 +         let (filenames, crate_types) = match msg {
19 +             CargoMessage::CompilerArtifact {
20 +                 filenames,
21 +                 target: CargoTarget { crate_types },
22 +                 ..
23 +             } => (filenames, crate_types),
24 +             _ => return,
25 +         };
26 +         for filename in filenames {
27 +             // Skip files like executables
28 +             if !(filename.ends_with(".rlib")
29 +                 || filename.ends_with(".lib")
30 +                 || filename.ends_with(".a")
31 +                 || is_debug_info(&filename)
32 +                 || is_dylib(&filename)
33 +                 || (is_check && filename.ends_with(".rmeta")))
34 +             {
35 +                 continue;
36 +             }
37 +         }
38 ~     });
   |

For more information about this error, try `rustc --explain E0061`.

Ideally the output should look like:

error[E0061]: this function takes 1 argument but 2 arguments were supplied
  --> src/lib.rs:17:14
   |
17 |     let ok = stream_cargo(vec![], &mut |msg| {
   |              ^^^^^^^^^^^^ ------ argument of type `Vec<_>` unexpected
   |
note: function defined here
  --> src/lib.rs:41:8
   |
41 | pub fn stream_cargo(
   |        ^^^^^^^^^^^^
42 |     cb: &mut dyn FnMut(CargoMessage),
   |     --------------------------------
help: remove the extra argument
   |
17 ~     let ok = stream_cargo(&mut |msg| {

Printing the entire body of the closure is ... a bit much 😆

[jyn514]

@estebank says

Namely it should be a multipart suggestion that only touches the parts that changed, not the whole arg list.

[Ezrashaw]

@rustbot claim

[jyn514]

@Ezrashaw fyi I think @estebank said they'd already started working on this, you might want to ask him how far he's gotten

[Ezrashaw]

@Ezrashaw fyi I think @estebank said they'd already started working on this, you might want to ask him how far he's gotten

Oh, if he is working on this then that's all fine, not really much point in duplicated work.

[estebank]

@Ezrashaw I did some work on this in #106347, but it only addresses removal of arguments and I would love it if you push it further, like fixing the case where removing multiple trailing arguments leaves behind a trailing comma.

[Ezrashaw]

@Ezrashaw I did some work on this in #106347, but it only addresses removal of arguments and I would love it if you push it further, like fixing the case where removing multiple trailing arguments leaves behind a trailing comma.

Ok, I'll have a look. Might be a little out of my skill level so if you or @jyn514 could mentor be a bit that would be great. I also haven't looked at your PR yet so I assume that would be a good place to start.

@rustbot claim

[Ezrashaw]

@estebank It appears you have fixed the trailing commas?