Allowing `clippy::unwrap_used` in const contexts

[Deewiant]

Description

clippy::unwrap_used and clippy::expect_used lint in const contexts, but that doesn't make much sense, because if the operations fail and panic, rustc will error out regardless. The fact that we are in a const context forms a guarantee in itself that the unwrap or expect call is fine.

See also: #9307

---

For example:

#![warn(clippy::unwrap_used)]
const X: Option<i32> = Some(42);
pub fn foo() -> i32 {
    const { X.unwrap() }
}

Reports:

warning: used `unwrap()` on an `Option` value
 --> asdf.rs:4:13
  |
4 |     const { X.unwrap() }
  |             ^^^^^^^^^^
  |
  = note: if this value is `None`, it will panic

But this is worthless, because if we change X to None, we get an error from rustc anyway:

error[E0080]: evaluation of `foo::{constant#0}` failed
 --> asdf.rs:4:13
  |
4 |     const { X.unwrap() }
  |             ^^^^^^^^^^ the evaluated program panicked at 'called `Option::unwrap()` on a `None` value', asdf.rs:4:15

Version

rustc 1.84.0 (9fc6b4312 2025-01-07)
binary: rustc
commit-hash: 9fc6b43126469e3858e2fe86cafb4f0fd5068869
commit-date: 2025-01-07
host: x86_64-unknown-linux-gnu
release: 1.84.0
LLVM version: 19.1.5

Additional Labels

@rustbot label +C-enhancement