Clippy doesn't know how to fix `arbitrary_self_type` in some async functions

[jyn514]

I tried the code from https://github.com/tokio-rs/tracing/blob/9ae4676054067dcf99b55cb76fcee3997207de6d/tracing-attributes/tests/async_fn.rs. Here is my attempt at an MCVE, but it doesn't compile:

use async_trait::async_trait;
use tracing_attributes::instrument;

#[async_trait]
pub trait Test {
    async fn call();
    async fn call_with_self(&self);
    async fn call_with_mut_self(&mut self);
}

#[derive(Clone, Debug)]
struct TestImpl;

#[async_trait]
impl Test for TestImpl {
    // instrumenting this is currently not possible, see https://github.com/tokio-rs/tracing/issues/864#issuecomment-667508801
    //#[instrument(fields(Self=std::any::type_name::<Self>()))]
    async fn call() {}

    #[instrument(fields(Self=std::any::type_name::<Self>()))]
    async fn call_with_self(&self) {}

    #[instrument(fields(Self=std::any::type_name::<Self>()))]
    async fn call_with_mut_self(self: &mut Self) {}
}

I expected to see this happen: cargo +nightly clippy --fix -Zunstable-options turns the code into async fn call_with_mut_self(&mut self) {}

Instead, this happened: Clippy replaces it with async fn call_with_mut_self(&'life0 mut self) {} which fails to compile.

error[E0261]: use of undeclared lifetime name `'life0`
   --> tracing-attributes/tests/async_fn.rs:226:38
    |
226 |         async fn call_with_mut_self(&'life0 mut self) {}
    |                                      ^^^^^^ undeclared lifetime
    |
    = help: if you want to experiment with in-band lifetime bindings, add `#![feature(in_band_lifetimes)]` to the crate attributes
help: consider introducing lifetime `'life0` here
    |
217 |     impl<'life0> Test for TestImpl {
    |         ^^^^^^^^
help: consider introducing lifetime `'life0` here
    |
216 |     'life0, #[async_trait]
    |     ^^^^^^^

error[E0261]: use of undeclared lifetime name `'life0`
   --> tracing-attributes/tests/async_fn.rs:226:38
    |
226 |         async fn call_with_mut_self(&'life0 mut self) {}
    |                                    - ^^^^^^ undeclared lifetime
    |                                    |
    |                                    help: consider introducing lifetime `'life0` here: `<'life0>`
    |
    = help: if you want to experiment with in-band lifetime bindings, add `#![feature(in_band_lifetimes)]` to the crate attributes

error[E0195]: lifetime parameters or bounds on method `call_with_mut_self` do not match the trait declaration
   --> tracing-attributes/tests/async_fn.rs:216:5
    |
206 |     #[async_trait]
    |     -------------- lifetimes in impl do not match this method in trait
...
216 |     #[async_trait]
    |     ^^^^^^^^^^^^^^ lifetimes do not match method in trait
    |
    = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)

Meta

• cargo clippy -V: clippy 0.0.212 (043f6d7 2020-09-25)
• rustc -V: rustc 1.46.0 (04488afe3 2020-08-24)

[ebroto]

I'm working on this one, should have a PR soon