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Move Try to module.
  • Loading branch information
Clar Charr committed Jun 9, 2017
commit bc9dc0ab3e26171da27fccf5775538e55c2a8e06
109 changes: 7 additions & 102 deletions src/libcore/ops/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -152,6 +152,7 @@ mod bit;
mod function;
mod place;
mod range;
mod try;

#[stable(feature = "rust1", since = "1.0.0")]
pub use self::arith::{Add, Sub, Mul, Div, Rem, Neg};
Expand All @@ -172,6 +173,12 @@ pub use self::range::{Range, RangeFrom, RangeFull, RangeTo};
#[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
pub use self::range::{RangeInclusive, RangeToInclusive};

#[unstable(feature = "question_mark_carrier", issue = "31436")]
#[cfg(stage0)]
pub use self::try::Carrier;
#[unstable(feature = "try_trait", issue = "42327")]
pub use self::try::Try;

#[unstable(feature = "placement_new_protocol", issue = "27779")]
pub use self::place::{Place, Placer, InPlace, Boxed, BoxPlace};

Expand Down Expand Up @@ -593,105 +600,3 @@ impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *mut T {}
// *const T -> *const U
#[unstable(feature = "coerce_unsized", issue = "27732")]
impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<*const U> for *const T {}

/// This trait has been superseded by the `Try` trait, but must remain
/// here as `?` is still lowered to it in stage0 .
#[cfg(stage0)]
#[unstable(feature = "question_mark_carrier", issue = "31436")]
pub trait Carrier {
/// The type of the value when computation succeeds.
type Success;
/// The type of the value when computation errors out.
type Error;

/// Create a `Carrier` from a success value.
fn from_success(_: Self::Success) -> Self;

/// Create a `Carrier` from an error value.
fn from_error(_: Self::Error) -> Self;

/// Translate this `Carrier` to another implementation of `Carrier` with the
/// same associated types.
fn translate<T>(self) -> T where T: Carrier<Success=Self::Success, Error=Self::Error>;
}

#[cfg(stage0)]
#[unstable(feature = "question_mark_carrier", issue = "31436")]
impl<U, V> Carrier for Result<U, V> {
type Success = U;
type Error = V;

fn from_success(u: U) -> Result<U, V> {
Ok(u)
}

fn from_error(e: V) -> Result<U, V> {
Err(e)
}

fn translate<T>(self) -> T
where T: Carrier<Success=U, Error=V>
{
match self {
Ok(u) => T::from_success(u),
Err(e) => T::from_error(e),
}
}
}

struct _DummyErrorType;

impl Try for _DummyErrorType {
type Ok = ();
type Error = ();

fn into_result(self) -> Result<Self::Ok, Self::Error> {
Ok(())
}

fn from_ok(_: ()) -> _DummyErrorType {
_DummyErrorType
}

fn from_error(_: ()) -> _DummyErrorType {
_DummyErrorType
}
}

/// A trait for customizing the behaviour of the `?` operator.
///
/// A type implementing `Try` is one that has a canonical way to view it
/// in terms of a success/failure dichotomy. This trait allows both
/// extracting those success or failure values from an existing instance and
/// creating a new instance from a success or failure value.
#[unstable(feature = "try_trait", issue = "42327")]
pub trait Try {
/// The type of this value when viewed as successful.
#[unstable(feature = "try_trait", issue = "42327")]
type Ok;
/// The type of this value when viewed as failed.
#[unstable(feature = "try_trait", issue = "42327")]
type Error;

/// Applies the "?" operator. A return of `Ok(t)` means that the
/// execution should continue normally, and the result of `?` is the
/// value `t`. A return of `Err(e)` means that execution should branch
/// to the innermost enclosing `catch`, or return from the function.
///
/// If an `Err(e)` result is returned, the value `e` will be "wrapped"
/// in the return type of the enclosing scope (which must itself implement
/// `Try`). Specifically, the value `X::from_error(From::from(e))`
/// is returned, where `X` is the return type of the enclosing function.
#[unstable(feature = "try_trait", issue = "42327")]
fn into_result(self) -> Result<Self::Ok, Self::Error>;

/// Wrap an error value to construct the composite result. For example,
/// `Result::Err(x)` and `Result::from_error(x)` are equivalent.
#[unstable(feature = "try_trait", issue = "42327")]
fn from_error(v: Self::Error) -> Self;

/// Wrap an OK value to construct the composite result. For example,
/// `Result::Ok(x)` and `Result::from_ok(x)` are equivalent.
#[unstable(feature = "try_trait", issue = "42327")]
fn from_ok(v: Self::Ok) -> Self;
}
111 changes: 111 additions & 0 deletions src/libcore/ops/try.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,111 @@
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/// This trait has been superseded by the `Try` trait, but must remain
/// here as `?` is still lowered to it in stage0 .
#[cfg(stage0)]
#[unstable(feature = "question_mark_carrier", issue = "31436")]
pub trait Carrier {
/// The type of the value when computation succeeds.
type Success;
/// The type of the value when computation errors out.
type Error;

/// Create a `Carrier` from a success value.
fn from_success(_: Self::Success) -> Self;

/// Create a `Carrier` from an error value.
fn from_error(_: Self::Error) -> Self;

/// Translate this `Carrier` to another implementation of `Carrier` with the
/// same associated types.
fn translate<T>(self) -> T where T: Carrier<Success=Self::Success, Error=Self::Error>;
}

#[cfg(stage0)]
#[unstable(feature = "question_mark_carrier", issue = "31436")]
impl<U, V> Carrier for Result<U, V> {
type Success = U;
type Error = V;

fn from_success(u: U) -> Result<U, V> {
Ok(u)
}

fn from_error(e: V) -> Result<U, V> {
Err(e)
}

fn translate<T>(self) -> T
where T: Carrier<Success=U, Error=V>
{
match self {
Ok(u) => T::from_success(u),
Err(e) => T::from_error(e),
}
}
}

struct _DummyErrorType;

impl Try for _DummyErrorType {
type Ok = ();
type Error = ();

fn into_result(self) -> Result<Self::Ok, Self::Error> {
Ok(())
}

fn from_ok(_: ()) -> _DummyErrorType {
_DummyErrorType
}

fn from_error(_: ()) -> _DummyErrorType {
_DummyErrorType
}
}

/// A trait for customizing the behaviour of the `?` operator.
///
/// A type implementing `Try` is one that has a canonical way to view it
/// in terms of a success/failure dichotomy. This trait allows both
/// extracting those success or failure values from an existing instance and
/// creating a new instance from a success or failure value.
#[unstable(feature = "try_trait", issue = "42327")]
pub trait Try {
/// The type of this value when viewed as successful.
#[unstable(feature = "try_trait", issue = "42327")]
type Ok;
/// The type of this value when viewed as failed.
#[unstable(feature = "try_trait", issue = "42327")]
type Error;

/// Applies the "?" operator. A return of `Ok(t)` means that the
/// execution should continue normally, and the result of `?` is the
/// value `t`. A return of `Err(e)` means that execution should branch
/// to the innermost enclosing `catch`, or return from the function.
///
/// If an `Err(e)` result is returned, the value `e` will be "wrapped"
/// in the return type of the enclosing scope (which must itself implement
/// `Try`). Specifically, the value `X::from_error(From::from(e))`
/// is returned, where `X` is the return type of the enclosing function.
#[unstable(feature = "try_trait", issue = "42327")]
fn into_result(self) -> Result<Self::Ok, Self::Error>;

/// Wrap an error value to construct the composite result. For example,
/// `Result::Err(x)` and `Result::from_error(x)` are equivalent.
#[unstable(feature = "try_trait", issue = "42327")]
fn from_error(v: Self::Error) -> Self;

/// Wrap an OK value to construct the composite result. For example,
/// `Result::Ok(x)` and `Result::from_ok(x)` are equivalent.
#[unstable(feature = "try_trait", issue = "42327")]
fn from_ok(v: Self::Ok) -> Self;
}