Clippy cognitive complexity false positive #553
Description
Bug Report
Version
tracing = "0.1"
cargo 1.40.0 (bc8e4c8be 2019-11-22)
clippy 0.0.212 (c8e3cfb 2019-10-28)
Platform
Linux ares 5.4.14-050414-generic #202001230832 SMP Thu Jan 23 08:34:56 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Description
When using tracing library to create an event in the match arms of an enum with six or more variants the Clippy 'cognitive complexity' warning is triggered.
Here is a minimal reproducer
fn main() {
println!("Clippy cognitive complexity repro");
fun(Run::There);
}
fn fun(r: Run) {
match r {
Run::Here => tracing::error!("error"),
Run::There => tracing::error!("error"),
Run::Everywhere => tracing::error!("error"),
Run::Makes => tracing::error!("error"),
Run::Clippy => tracing::error!("error"),
Run::Choke => tracing::error!("error"),
}
}
#[allow(dead_code)]
enum Run {
Here,
There,
Everywhere,
Makes,
Clippy,
Choke,
}
And Clippy gives the following warning:
cargo clippy
warning: the function has a cognitive complexity of (26/25)
--> src/main.rs:7:1
|
7 | / fn fun(r: Run) {
8 | | match r {
9 | | Run::Here => tracing::error!("error"),
10 | | Run::There => tracing::error!("error"),
... |
15 | | }
16 | | }
| |_^
|
= note: `#[warn(clippy::cognitive_complexity)]` on by default
= help: you could split it up into multiple smaller functions
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#cognitive_complexity
Removing the final variant (Choke) removes the warning.