Allow unused_must_use on result with never type

[TheZoq2]

#![feature(never_type)]

fn will_not_fail() -> Result<i32, !> {
    Ok(5)
}

pub fn main() {
    will_not_fail();
}

This code yields a warning:

warning: unused `std::result::Result` that must be used
 --> main.rs:8:5
  |
8 |     will_not_fail();
  |     ^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(unused_must_use)]` on by default
  = note: this `Result` may be an `Err` variant, which should be handled

However since a Result<T, !> can never have the Err branch, having to handle the resulting error seems kind of pointless. Would it be possible to disable the unused_must_use lint for this particular case?

[TeXitoi]

I'd prefer to have a get method:

impl<T> Result<T, !> {
    pub fn get(self) -> T {
        // can't panic
        self.unwrap()
    }
}

[RustyYato]

@TeXitoi to be more explicit about what we are doing, we can do

impl<T> Result<T, !> {
    pub fn get(self) -> T {
        match self {
            Ok(value) => value,
            Err(never) => never
        }
    }
}

[WaffleLapkin]

In recent Rust versions it's possible to unwrap Result<T, !> just by pattern matching (play):

#![feature(never_type)]

fn will_not_fail() -> Result<i32, !> {
    Ok(5)
}

pub fn main() {
    let Ok(x) = will_not_fail();
}