clippy::try_err: returning an `Err(_)` with the `?` operator

What you see

warning: returning an `Err(_)` with the `?` operator
 --> main.rs:5:7
  |
5 |       Err("failed")?;
  |       ^^^^^^^^^^^^^^ help: try: `return Err("failed".into())`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#try_err
  = note: requested on the command line with `-W clippy::try-err`

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

The ? operator is designed to allow calls that can fail to be easily chained. For example, foo()?.bar() or foo(bar()?). Because Err(x)? can’t be used that way (it will always return), it is more clear to write return Err(x).

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

fn foo(fail: bool) -> Result<i32, String> {
    if fail {
      Err("failed")?;
    }
    Ok(0)
}

Write this instead

fn foo(fail: bool) -> Result<i32, String> {
    if fail {
      return Err("failed".into());
    }
    Ok(0)
}

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

[lints.clippy]
try_err = "warn"

#![warn(clippy::try_err)]

cargo clippy -- -W clippy::try-err

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.