`unused_parens` suggestion yeets attribute

[matthiaskrgr]

Using the following flags

--force-warn unused_parens

this code:

#![feature(contracts)]

#[core::contracts::requires(x.baz > 0)]
#[core::contracts::ensures(|ret| *ret > 100)]
fn nest(x: Baz) -> i32
{
    loop {
        return x.baz + 50;
    }
}

struct Baz { baz: i32 }

fn main() {}

caused the following diagnostics:

    Blocking waiting for file lock on package cache
    Blocking waiting for file lock on package cache
    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.mjalOFICDlk5/icemaker_clippyfix_tempdir.rnyxLGd0A92q/_a)
warning: unnecessary parentheses around closure body
 --> src/main.rs:3:1
  |
3 | #[core::contracts::requires(x.baz > 0)]
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^         ^^
  |
  = note: requested on the command line with `--force-warn unused-parens`
help: remove these parentheses
  |
3 - #[core::contracts::requires(x.baz > 0)]
3 + x.baz > 0
  |

warning: `_a` (bin "_a") generated 1 warning (run `cargo clippy --fix --bin "_a"` to apply 1 suggestion)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.36s

However after applying these diagnostics, the resulting code:

#![feature(contracts)]

x.baz > 0
#[core::contracts::ensures(|ret| *ret > 100)]
fn nest(x: Baz) -> i32
{
    loop {
        return x.baz + 50;
    }
}

struct Baz { baz: i32 }

fn main() {}

no longer compiled:

    Blocking waiting for file lock on package cache
    Blocking waiting for file lock on package cache
    Checking _a v0.1.0 (/tmp/icemaker_global_tempdir.mjalOFICDlk5/icemaker_clippyfix_tempdir.rnyxLGd0A92q/_a)
error: expected one of `!` or `::`, found `.`
 --> src/main.rs:3:2
  |
3 | x.baz > 0
  |  ^ expected one of `!` or `::`

error: could not compile `_a` (bin "_a" test) due to 1 previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `_a` (bin "_a") due to 1 previous error

Version:

rustc 1.90.0-nightly (78a6e1329 2025-07-10)
binary: rustc
commit-hash: 78a6e132984dba0303ebad7dcfd1305c93ad5835
commit-date: 2025-07-10
host: x86_64-unknown-linux-gnu
release: 1.90.0-nightly
LLVM version: 20.1.7

[matthiaskrgr]

could be related to #136906