identity_conversion false positive with ? for loops in 1.35

[sfackler]

This may be a duplicate of #4081, but I can't easily check since clippy isn't in the current nightly.

fn foo() -> Result<Vec<u8>, ()> {
    Err(())
}

fn bar() -> Result<(), ()> {
    for _ in foo()? {}

    Ok(())
}

warning: identical conversion
 --> src/main.rs:6:14
  |
6 |     for _ in foo()? {}
  |              ^^^^^^ help: consider removing `foo()?()`: `foo()?`
  |
  = note: #[warn(clippy::identity_conversion)] on by default
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#identity_conversion

[hoodie]

ditto: seeing lots of those when I iterare over Result<Vec<_>> with ?

[baumanj]

Seeing this in 1.34 as well

[flip1995]

Yes this is fixed in #4083 and will be available in the next nightly Clippy.

[Manishearth]

Should we beta backport?

[flip1995]

I think that would be the right thing to do.

[oli-obk]

@flip1995 that issue link (4083) is not pointing to a PR. I have been unable to find the PR that fixed it.

[flip1995]

Oh sorry, it was the #4082 PR, the test for this is in #4089

[oli-obk]

I just checked, all of that PR is in the current beta, so we're good

[wraithan]

Looks like this is broken on the clippy that comes with stable via rustup component add clippy on rust 1.35.0

[~/devel/rust/shader-playground] master(1)+* ± rustc --version && cargo --version && cargo clippy -- --version
rustc 1.35.0 (3c235d560 2019-05-20)
cargo 1.35.0 (6f3e9c367 2019-04-04)
clippy 0.0.212 (265318db 2019-05-17)
[~/devel/rust/shader-playground] master(1)+* ± cargo clippy
    Checking shader-playground v0.1.0 (/Users/wraithan/devel/rust/shader-playground)
error: identical conversion
   --> src/shader.rs:181:18
    |
181 |     for entry in std::fs::read_dir(dir)? {
    |                  ^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `std::fs::read_dir(dir)?()`: `std::fs::read_dir(dir)?`
    |