2018-07-24 17:24:12 +00:00
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#![feature(rustc_private)]
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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.
2014-12-26 08:30:51 +00:00
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2014-05-11 04:46:46 +00:00
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extern crate serialize;
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2018-09-17 09:48:20 +00:00
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use serialize as rustc_serialize;
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2014-03-02 00:33:24 +00:00
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2013-06-13 13:16:30 +00:00
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mod submod {
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// if any of these are implemented without global calls for any
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// function calls, then being in a submodule will (correctly)
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// cause errors about unrecognised module `std` (or `extra`)
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2014-12-31 04:32:49 +00:00
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#[derive(PartialEq, PartialOrd, Eq, Ord,
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2014-02-24 03:11:19 +00:00
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Hash,
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2014-03-05 06:19:14 +00:00
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Clone,
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2015-04-10 18:12:43 +00:00
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Debug,
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2018-09-17 09:48:20 +00:00
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RustcEncodable, RustcDecodable)]
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2015-03-26 00:06:52 +00:00
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enum A { A1(usize), A2(isize) }
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2013-06-13 13:16:30 +00:00
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2014-12-31 04:32:49 +00:00
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#[derive(PartialEq, PartialOrd, Eq, Ord,
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2014-02-24 03:11:19 +00:00
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Hash,
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2014-03-05 06:19:14 +00:00
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Clone,
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2015-04-10 18:12:43 +00:00
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Debug,
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2018-09-17 09:48:20 +00:00
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RustcEncodable, RustcDecodable)]
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2015-03-26 00:06:52 +00:00
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struct B { x: usize, y: isize }
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2013-06-13 13:16:30 +00:00
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2014-12-31 04:32:49 +00:00
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#[derive(PartialEq, PartialOrd, Eq, Ord,
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2014-02-24 03:11:19 +00:00
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Hash,
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2014-03-05 06:19:14 +00:00
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Clone,
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2015-04-10 18:12:43 +00:00
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Debug,
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2018-09-17 09:48:20 +00:00
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RustcEncodable, RustcDecodable)]
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2015-03-26 00:06:52 +00:00
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struct C(usize, isize);
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2013-06-13 13:16:30 +00:00
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}
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2014-01-03 23:30:54 +00:00
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pub fn main() {}
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