rust/src/test/run-pass/deriving-global.rs

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// Copyright 2014 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.
#![feature(old_orphan_check, rand, rustc_private)]
Fix orphan checking (cc #19470). (This is not a complete fix of #19470 because of the backwards compatibility feature gate.) This is a [breaking-change]. The new rules require that, for an impl of a trait defined in some other crate, two conditions must hold: 1. Some type must be local. 2. Every type parameter must appear "under" some local type. Here are some examples that are legal: ```rust struct MyStruct<T> { ... } // Here `T` appears "under' `MyStruct`. impl<T> Clone for MyStruct<T> { } // Here `T` appears "under' `MyStruct` as well. Note that it also appears // elsewhere. impl<T> Iterator<T> for MyStruct<T> { } ``` Here is an illegal example: ```rust // Here `U` does not appear "under" `MyStruct` or any other local type. // We call `U` "uncovered". impl<T,U> Iterator<U> for MyStruct<T> { } ``` There are a couple of ways to rewrite this last example so that it is legal: 1. In some cases, the uncovered type parameter (here, `U`) should be converted into an associated type. This is however a non-local change that requires access to the original trait. Also, associated types are not fully baked. 2. Add `U` as a type parameter of `MyStruct`: ```rust struct MyStruct<T,U> { ... } impl<T,U> Iterator<U> for MyStruct<T,U> { } ``` 3. Create a newtype wrapper for `U` ```rust impl<T,U> Iterator<Wrapper<U>> for MyStruct<T,U> { } ``` Because associated types are not fully baked, which in the case of the `Hash` trait makes adhering to this rule impossible, you can temporarily disable this rule in your crate by using `#![feature(old_orphan_check)]`. Note that the `old_orphan_check` feature will be removed before 1.0 is released.
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extern crate serialize;
extern crate rand;
mod submod {
// if any of these are implemented without global calls for any
// function calls, then being in a submodule will (correctly)
// cause errors about unrecognised module `std` (or `extra`)
#[derive(PartialEq, PartialOrd, Eq, Ord,
Hash,
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Clone,
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Debug, Rand,
Encodable, Decodable)]
enum A { A1(uint), A2(int) }
#[derive(PartialEq, PartialOrd, Eq, Ord,
Hash,
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Clone,
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Debug, Rand,
Encodable, Decodable)]
struct B { x: uint, y: int }
#[derive(PartialEq, PartialOrd, Eq, Ord,
Hash,
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Clone,
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Debug, Rand,
Encodable, Decodable)]
struct C(uint, int);
}
pub fn main() {}