Errors are too verbose since 1.72.0

[bytefall]

Code

// cargo new testx
// cd testx
// cargo add tokio -F full
#[tokio::main]
async fn main() -> Result<(), impl std::error::Error> {
    tokio::spawn(run()).await
}

async fn run() {
    let i: u8 = ""; // E0308 is here
}

Current output

Checking testx v0.1.0 (/tmp/testx)
error[E0308]: mismatched types
 --> src/main.rs:7:17
  |
7 |     let i: u8 = "";
  |            --   ^^ expected `u8`, found `&str`
  |            |
  |            expected due to this

error: cannot check whether the hidden type of opaque type satisfies auto traits
   --> src/main.rs:3:18
    |
3   |     tokio::spawn(run()).await
    |     ------------ ^^^^^
    |     |
    |     required by a bound introduced by this call
    |
note: opaque type is declared here
   --> src/main.rs:6:16
    |
6   | async fn run() {
    |                ^
note: this item depends on auto traits of the hidden type, but may also be registering the hidden type. This is not supported right now. You can try moving the opaque type and the item that actually registers a hidden type into a new submodule
   --> src/main.rs:2:10
    |
2   | async fn main() -> Result<(), impl std::error::Error> {
    |          ^^^^
note: required by a bound in `tokio::spawn`
   --> /home/user/.cargo/registry/src/index.crates.io-6f17d22bba15001f/tokio-1.32.0/src/task/spawn.rs:166:21
    |
164 |     pub fn spawn<T>(future: T) -> JoinHandle<T::Output>
    |            ----- required by a bound in this function
165 |     where
166 |         T: Future + Send + 'static,
    |                     ^^^^ required by this bound in `spawn`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `testx` (bin "testx") due to 2 previous errors

Desired output

Checking testx v0.1.0 (/tmp/2/testx)
error[E0308]: mismatched types
 --> src/main.rs:7:17
  |
7 |     let i: u8 = "";
  |            --   ^^ expected `u8`, found `&str`
  |            |
  |            expected due to this

For more information about this error, try `rustc --explain E0308`.
error: could not compile `testx` (bin "testx") due to previous error

Rationale and extra context

Something has changed in rustc 1.72.0. Error diagnostics become too verbose.

Provided example contains E0308 which is hard to locate due to verbose trait bounds description. With more async code it's getting even worse.

Previous version 1.71.0 shows only the place where an actual error is (see "desired output").

Other cases

No response

Anything else?

No response

[compiler-errors]

This should be fixed by #115294. Can you see if this error continues to be triggered on nightly?

[atsuzaki]

It's fixed in the latest nightly (1.74.0-nightly 2023-08-29 84a9f4c) https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=92ffa9a7006de803740f77c23168d192

We can close this?