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let-and-return suggests syntactically incorrect as _ syntax #9976

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@matthiaskrgr

Description

@matthiaskrgr

Summary

.

Reproducer

I tried this code:

// Test various stacked-borrows-related things.
const fn main() {}

pub const fn read_does_not_invalidate2() {
    fn _foo(x: &mut (i32, i32)) -> &i32 {
        let xraw = x as *mut (i32, i32);
        let ret = unsafe { &(*xraw).1 };
        ret
    }
}

after fixes were automatically applied the compiler reported errors within these files:

  * src/main.rs

This likely indicates a bug in either rustc or cargo itself,
and we would appreciate a bug report! You're likely to see
a number of compiler warnings after this message which cargo
attempted to fix but failed. If you could open an issue at
https://github.com/rust-lang/rust/issues
quoting the full output of this command we'd be very appreciative!
Note that you may be able to make some more progress in the near-term
fixing code with the `--broken-code` flag

The following errors were reported:
error: expected expression, found `as`
 --> src/main.rs:8:31
  |
8 |         unsafe { &(*xraw).1 } as _
  |                               ^^ expected expression
  |
help: parentheses are required to parse this as an expression
  |
8 |         (unsafe { &(*xraw).1 }) as _
  |         +                     +

error: aborting due to previous error

Original diagnostics will follow.

warning: returning the result of a `let` binding from a block
 --> src/main.rs:8:9
  |
7 |         let ret = unsafe { &(*xraw).1 };
  |         -------------------------------- unnecessary `let` binding
8 |         ret
  |         ^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return
  = note: `-W clippy::let-and-return` implied by `-W clippy::all`
help: return the expression directly
  |
7 ~
8 ~         unsafe { &(*xraw).1 } as _
  |

Version

rustc 1.67.0-nightly (1eb62b123 2022-11-27)
binary: rustc
commit-hash: 1eb62b1235fd77200e6bd967d70e83c0f2497233
commit-date: 2022-11-27
host: x86_64-unknown-linux-gnu
release: 1.67.0-nightly
LLVM version: 15.0.4

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    C-bugCategory: Clippy is not doing the correct thingI-suggestion-causes-errorIssue: The suggestions provided by this Lint cause an ICE/error when applied

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