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Rollup merge of rust-lang#43426 - qnighy:intercrate-ambiguity-hints, …
…r=nikomatsakis Add hints when intercrate ambiguity causes overlap. I'm going to tackle rust-lang#23980. # Examples ## Trait impl overlap caused by possible downstream impl ```rust trait Foo<X> {} trait Bar<X> {} impl<X, T> Foo<X> for T where T: Bar<X> {} impl<X> Foo<X> for i32 {} fn main() {} ``` ``` error[E0119]: conflicting implementations of trait `Foo<_>` for type `i32`: --> test1.rs:4:1 | 3 | impl<X, T> Foo<X> for T where T: Bar<X> {} | ------------------------------------------ first implementation here 4 | impl<X> Foo<X> for i32 {} | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `i32` | = note: downstream crates may implement Bar error: aborting due to previous error ``` ## Trait impl overlap caused by possible upstream update ```rust trait Foo {} impl<T> Foo for T where T: ::std::fmt::Octal {} impl Foo for () {} fn main() {} ``` ``` error[E0119]: conflicting implementations of trait `Foo` for type `()`: --> test2.rs:3:1 | 2 | impl<T> Foo for T where T: ::std::fmt::Octal {} | ----------------------------------------------- first implementation here 3 | impl Foo for () {} | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `()` | = note: upstream crates may add new impl for std::fmt::Octal in future versions error: aborting due to previous error ``` ## Inherent impl overlap caused by possible downstream impl ```rust trait Bar<X> {} struct A<T, X>(T, X); impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} } impl<X> A<i32, X> { fn f(&self) {} } fn main() {} ``` ``` error[E0592]: duplicate definitions with name `f` --> test3.rs:4:38 | 4 | impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} } | ^^^^^^^^^^^^^^ duplicate definitions for `f` 5 | impl<X> A<i32, X> { fn f(&self) {} } | -------------- other definition for `f` | = note: downstream crates may implement Bar error: aborting due to previous error ``` ## Inherent impl overlap caused by possible upstream update ```rust struct A<T>(T); impl<T> A<T> where T: ::std::fmt::Octal { fn f(&self) {} } impl A<()> { fn f(&self) {} } fn main() {} ``` ``` error[E0592]: duplicate definitions with name `f` --> test4.rs:3:43 | 3 | impl<T> A<T> where T: ::std::fmt::Octal { fn f(&self) {} } | ^^^^^^^^^^^^^^ duplicate definitions for `f` 4 | impl A<()> { fn f(&self) {} } | -------------- other definition for `f` | = note: upstream crates may add new impl for std::fmt::Octal in future versions error: aborting due to previous error ```
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src/test/compile-fail/coherence-overlap-downstream-inherent.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| // Copyright 2017 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. | ||
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| // Tests that we consider `T: Sugar + Fruit` to be ambiguous, even | ||
| // though no impls are found. | ||
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| struct Sweet<X>(X); | ||
| pub trait Sugar {} | ||
| pub trait Fruit {} | ||
| impl<T:Sugar> Sweet<T> { fn dummy(&self) { } } | ||
| //~^ ERROR E0592 | ||
| //~| NOTE duplicate definitions for `dummy` | ||
| impl<T:Fruit> Sweet<T> { fn dummy(&self) { } } | ||
| //~^ NOTE other definition for `dummy` | ||
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| trait Bar<X> {} | ||
| struct A<T, X>(T, X); | ||
| impl<X, T> A<T, X> where T: Bar<X> { fn f(&self) {} } | ||
| //~^ ERROR E0592 | ||
| //~| NOTE duplicate definitions for `f` | ||
| //~| NOTE downstream crates may implement trait `Bar<_>` for type `i32` | ||
| impl<X> A<i32, X> { fn f(&self) {} } | ||
| //~^ NOTE other definition for `f` | ||
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| fn main() {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,32 @@ | ||
| // Copyright 2017 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. | ||
|
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| // Tests that we consider `T: Sugar + Fruit` to be ambiguous, even | ||
| // though no impls are found. | ||
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| pub trait Sugar {} | ||
| pub trait Fruit {} | ||
| pub trait Sweet {} | ||
| impl<T:Sugar> Sweet for T { } | ||
| //~^ NOTE first implementation here | ||
| impl<T:Fruit> Sweet for T { } | ||
| //~^ ERROR E0119 | ||
| //~| NOTE conflicting implementation | ||
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| pub trait Foo<X> {} | ||
| pub trait Bar<X> {} | ||
| impl<X, T> Foo<X> for T where T: Bar<X> {} | ||
| //~^ NOTE first implementation here | ||
| impl<X> Foo<X> for i32 {} | ||
| //~^ ERROR E0119 | ||
| //~| NOTE conflicting implementation for `i32` | ||
| //~| NOTE downstream crates may implement trait `Bar<_>` for type `i32` | ||
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| fn main() { } |
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