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Fix the types in one of the FromResidual implementations #1645

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44 changes: 38 additions & 6 deletions core/lib/src/outcome.rs
Original file line number Diff line number Diff line change
Expand Up @@ -603,21 +603,19 @@ impl<S, E, F> Outcome<S, E, F> {
}
}

impl<Y, S, E: From<Y>, F> FromResidual<Result<!, Y>> for Outcome<S, E, F> {
fn from_residual(r: Result<!, Y>) -> Self {
#[allow(unreachable_code)]
impl<Y, S, E: From<Y>, F> FromResidual<Result<std::convert::Infallible, Y>> for Outcome<S, E, F> {
fn from_residual(r: Result<std::convert::Infallible, Y>) -> Self {
match r {
Ok(v) => Outcome::Success(v),
Ok(never) => match never {},
Err(y) => Outcome::Failure(y.into()),
}
}
}

impl<S, X, E: From<X>, Y, F: From<Y>> FromResidual<Outcome<!, X, Y>> for Outcome<S, E, F> {
fn from_residual(r: Outcome<!, X, Y>) -> Self {
#[allow(unreachable_code)]
match r {
Outcome::Success(s) => Outcome::Success(s),
Outcome::Success(never) => match never {},
Outcome::Failure(x) => Outcome::Failure(x.into()),
Outcome::Forward(y) => Outcome::Forward(y.into()),
}
Expand Down Expand Up @@ -654,3 +652,37 @@ impl<S, E, F> fmt::Display for Outcome<S, E, F> {
write!(f, "{}", Paint::default(string).fg(color))
}
}

#[cfg(test)]
mod test {
use super::Outcome::{self, *};

macro_rules! fake_try {
($e:block) => {
(||{
std::ops::Try::from_output($e)
})()
}
}

#[test]
fn outcome_try_trait() {
let r: Outcome<u16, String, f64> = fake_try! {{ 3 }};
assert_eq!(r, Success(3));
let r: Outcome<u16, String, f64> = fake_try! {{ Success::<_, &'static str, f32>(3)? }};
assert_eq!(r, Success(3));
let r: Outcome<u16, String, f64> = fake_try! {{ Failure::<u64, _, f32>("oops")?; 7 }};
assert_eq!(r, Failure(String::from("oops")));
let r: Outcome<u16, String, f64> = fake_try! {{ Forward::<u64, &'static str, _>(1234.5_f32)?; 7 }};
assert_eq!(r, Forward(1234.5));
}

#[test]
fn can_use_question_mark_on_result_in_function_returning_outcome() {
fn demo() -> Outcome<i128, String, f32> {
Err("problem")?;
unreachable!()
}
assert_eq!(demo(), Failure(String::from("problem")));
}
}