make a custom error for overlap with negative impls

18 files changed, 93 insertions, 107 deletions

diff --git a/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.rs b/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.rs
index b4f5f9ef56b..0fabb5ec91d 100644
--- a/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.rs
+++ b/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.rs
@@ -6,13 +6,11 @@ trait MyTrait {}
 
 struct TestType<T>(::std::marker::PhantomData<T>);
 
-unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
+unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
 
-impl<T: MyTrait> !Send for TestType<T> {}
-//~^ ERROR conflicting implementations
+impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR found both positive and negative implementation
 
-unsafe impl<T:'static> Send for TestType<T> {}
-//~^ ERROR conflicting implementations
+unsafe impl<T: 'static> Send for TestType<T> {} //~ ERROR conflicting implementations
 
 impl !Send for TestType<i32> {}
 
diff --git a/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.stderr b/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
index 25d3d3ee997..5081536b702 100644
--- a/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
+++ b/src/test/ui/coherence/coherence-conflicting-negative-trait-impl.stderr
@@ -1,21 +1,22 @@
-error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`:
+error[E0748]: found both positive and negative implementation of trait `std::marker::Send` for type `TestType<_>`:
   --> $DIR/coherence-conflicting-negative-trait-impl.rs:11:1
    |
-LL | unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
-   | ---------------------------------------------------- first implementation here
+LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
+   | ------------------------------------------------------ positive implementation here
 LL | 
 LL | impl<T: MyTrait> !Send for TestType<T> {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`:
-  --> $DIR/coherence-conflicting-negative-trait-impl.rs:14:1
+  --> $DIR/coherence-conflicting-negative-trait-impl.rs:13:1
    |
-LL | unsafe impl<T: MyTrait+'static> Send for TestType<T> {}
-   | ---------------------------------------------------- first implementation here
+LL | unsafe impl<T: MyTrait + 'static> Send for TestType<T> {}
+   | ------------------------------------------------------ first implementation here
 ...
-LL | unsafe impl<T:'static> Send for TestType<T> {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
+LL | unsafe impl<T: 'static> Send for TestType<T> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0119`.
+Some errors have detailed explanations: E0119, E0748.
+For more information about an error, try `rustc --explain E0119`.
diff --git a/src/test/ui/issues/issue-33140-hack-boundaries.rs b/src/test/ui/issues/issue-33140-hack-boundaries.rs
index fbdef51c132..5aba886273f 100644
--- a/src/test/ui/issues/issue-33140-hack-boundaries.rs
+++ b/src/test/ui/issues/issue-33140-hack-boundaries.rs
@@ -4,8 +4,7 @@
 // Check that the issue #33140 hack does not allow unintended things.
 
 // OK
-trait Trait0 {
-}
+trait Trait0 {}
 
 impl Trait0 for dyn Send {}
 impl Trait0 for dyn Send {}
@@ -20,58 +19,49 @@ impl Trait1 for dyn Send {}
 //~^ ERROR E0119
 
 // Problem 2: negative impl
-trait Trait2 {
-}
+trait Trait2 {}
 
 impl Trait2 for dyn Send {}
 impl !Trait2 for dyn Send {}
-//~^ ERROR E0119
-
+//~^ ERROR E0748
 
 // Problem 3: type parameter
-trait Trait3<T: ?Sized> {
-}
+trait Trait3<T: ?Sized> {}
 
 impl Trait3<dyn Sync> for dyn Send {}
 impl Trait3<dyn Sync> for dyn Send {}
 //~^ ERROR E0119
 
 // Problem 4a: not a trait object - generic
-trait Trait4a {
-}
+trait Trait4a {}
 
 impl<T: ?Sized> Trait4a for T {}
 impl Trait4a for dyn Send {}
 //~^ ERROR E0119
 
 // Problem 4b: not a trait object - misc
-trait Trait4b {
-}
+trait Trait4b {}
 
 impl Trait4b for () {}
 impl Trait4b for () {}
 //~^ ERROR E0119
 
 // Problem 4c: not a principal-less trait object
-trait Trait4c {
-}
+trait Trait4c {}
 
 impl Trait4c for dyn Trait1 + Send {}
 impl Trait4c for dyn Trait1 + Send {}
 //~^ ERROR E0119
 
 // Problem 4d: lifetimes
-trait Trait4d {
-}
+trait Trait4d {}
 
 impl<'a> Trait4d for dyn Send + 'a {}
 impl<'a> Trait4d for dyn Send + 'a {}
 //~^ ERROR E0119
 
-
 // Problem 5: where-clauses
-trait Trait5 {
-}
+trait Trait5 {}
 
 impl Trait5 for dyn Send {}
 impl Trait5 for dyn Send where u32: Copy {}
diff --git a/src/test/ui/issues/issue-33140-hack-boundaries.stderr b/src/test/ui/issues/issue-33140-hack-boundaries.stderr
index 95aaa55ba7c..b3bf34a2a90 100644
--- a/src/test/ui/issues/issue-33140-hack-boundaries.stderr
+++ b/src/test/ui/issues/issue-33140-hack-boundaries.stderr
@@ -1,21 +1,21 @@
 error[E0119]: conflicting implementations of trait `Trait1` for type `(dyn std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:19:1
+  --> $DIR/issue-33140-hack-boundaries.rs:18:1
    |
 LL | impl Trait1 for dyn Send {}
    | ------------------------ first implementation here
 LL | impl Trait1 for dyn Send {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
 
-error[E0119]: conflicting implementations of trait `Trait2` for type `(dyn std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:27:1
+error[E0748]: found both positive and negative implementation of trait `Trait2` for type `(dyn std::marker::Send + 'static)`:
+  --> $DIR/issue-33140-hack-boundaries.rs:25:1
    |
 LL | impl Trait2 for dyn Send {}
-   | ------------------------ first implementation here
+   | ------------------------ positive implementation here
 LL | impl !Trait2 for dyn Send {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error[E0119]: conflicting implementations of trait `Trait3<(dyn std::marker::Sync + 'static)>` for type `(dyn std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:36:1
+  --> $DIR/issue-33140-hack-boundaries.rs:32:1
    |
 LL | impl Trait3<dyn Sync> for dyn Send {}
    | ---------------------------------- first implementation here
@@ -23,7 +23,7 @@ LL | impl Trait3<dyn Sync> for dyn Send {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
 
 error[E0119]: conflicting implementations of trait `Trait4a` for type `(dyn std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:44:1
+  --> $DIR/issue-33140-hack-boundaries.rs:39:1
    |
 LL | impl<T: ?Sized> Trait4a for T {}
    | ----------------------------- first implementation here
@@ -31,7 +31,7 @@ LL | impl Trait4a for dyn Send {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn std::marker::Send + 'static)`
 
 error[E0119]: conflicting implementations of trait `Trait4b` for type `()`:
-  --> $DIR/issue-33140-hack-boundaries.rs:52:1
+  --> $DIR/issue-33140-hack-boundaries.rs:46:1
    |
 LL | impl Trait4b for () {}
    | ------------------- first implementation here
@@ -39,7 +39,7 @@ LL | impl Trait4b for () {}
    | ^^^^^^^^^^^^^^^^^^^ conflicting implementation for `()`
 
 error[E0119]: conflicting implementations of trait `Trait4c` for type `(dyn Trait1 + std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:60:1
+  --> $DIR/issue-33140-hack-boundaries.rs:53:1
    |
 LL | impl Trait4c for dyn Trait1 + Send {}
    | ---------------------------------- first implementation here
@@ -47,7 +47,7 @@ LL | impl Trait4c for dyn Trait1 + Send {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(dyn Trait1 + std::marker::Send + 'static)`
 
 error[E0119]: conflicting implementations of trait `Trait4d` for type `dyn std::marker::Send`:
-  --> $DIR/issue-33140-hack-boundaries.rs:68:1
+  --> $DIR/issue-33140-hack-boundaries.rs:60:1
    |
 LL | impl<'a> Trait4d for dyn Send + 'a {}
    | ---------------------------------- first implementation here
@@ -55,7 +55,7 @@ LL | impl<'a> Trait4d for dyn Send + 'a {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `dyn std::marker::Send`
 
 error[E0119]: conflicting implementations of trait `Trait5` for type `(dyn std::marker::Send + 'static)`:
-  --> $DIR/issue-33140-hack-boundaries.rs:77:1
+  --> $DIR/issue-33140-hack-boundaries.rs:67:1
    |
 LL | impl Trait5 for dyn Send {}
    | ------------------------ first implementation here
@@ -64,4 +64,5 @@ LL | impl Trait5 for dyn Send where u32: Copy {}
 
 error: aborting due to 8 previous errors
 
-For more information about this error, try `rustc --explain E0119`.
+Some errors have detailed explanations: E0119, E0748.
+For more information about an error, try `rustc --explain E0119`.
diff --git a/src/test/ui/specialization/specialization-overlap-negative.rs b/src/test/ui/specialization/specialization-overlap-negative.rs
index af80d6686e3..4f5f65dafaa 100644
--- a/src/test/ui/specialization/specialization-overlap-negative.rs
+++ b/src/test/ui/specialization/specialization-overlap-negative.rs
@@ -6,6 +6,6 @@ trait MyTrait {}
 struct TestType<T>(::std::marker::PhantomData<T>);
 
 unsafe impl<T: Clone> Send for TestType<T> {}
-impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR E0119
+impl<T: MyTrait> !Send for TestType<T> {} //~ ERROR E0748
 
 fn main() {}
diff --git a/src/test/ui/specialization/specialization-overlap-negative.stderr b/src/test/ui/specialization/specialization-overlap-negative.stderr
index 947aad824ea..cbc7271b199 100644
--- a/src/test/ui/specialization/specialization-overlap-negative.stderr
+++ b/src/test/ui/specialization/specialization-overlap-negative.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `std::marker::Send` for type `TestType<_>`:
+error[E0748]: found both positive and negative implementation of trait `std::marker::Send` for type `TestType<_>`:
   --> $DIR/specialization-overlap-negative.rs:9:1
    |
 LL | unsafe impl<T: Clone> Send for TestType<T> {}
-   | ------------------------------------------ first implementation here
+   | ------------------------------------------ positive implementation here
 LL | impl<T: MyTrait> !Send for TestType<T> {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `TestType<_>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/specialization/specialization-polarity.rs b/src/test/ui/specialization/specialization-polarity.rs
index d5744806745..fd0671ad09e 100644
--- a/src/test/ui/specialization/specialization-polarity.rs
+++ b/src/test/ui/specialization/specialization-polarity.rs
@@ -6,11 +6,11 @@
 auto trait Foo {}
 
 impl<T> Foo for T {}
-impl !Foo for u8 {} //~ ERROR E0119
+impl !Foo for u8 {} //~ ERROR E0748
 
 auto trait Bar {}
 
 impl<T> !Bar for T {}
-impl Bar for u8 {} //~ ERROR E0119
+impl Bar for u8 {} //~ ERROR E0748
 
 fn main() {}
diff --git a/src/test/ui/specialization/specialization-polarity.stderr b/src/test/ui/specialization/specialization-polarity.stderr
index bc1b2aeb70f..c6e7f193d01 100644
--- a/src/test/ui/specialization/specialization-polarity.stderr
+++ b/src/test/ui/specialization/specialization-polarity.stderr
@@ -1,19 +1,19 @@
-error[E0119]: conflicting implementations of trait `Foo` for type `u8`:
+error[E0748]: found both positive and negative implementation of trait `Foo` for type `u8`:
   --> $DIR/specialization-polarity.rs:9:1
    |
 LL | impl<T> Foo for T {}
-   | ----------------- first implementation here
+   | ----------------- positive implementation here
 LL | impl !Foo for u8 {}
-   | ^^^^^^^^^^^^^^^^ conflicting implementation for `u8`
+   | ^^^^^^^^^^^^^^^^ negative implementation here
 
-error[E0119]: conflicting implementations of trait `Bar` for type `u8`:
+error[E0748]: found both positive and negative implementation of trait `Bar` for type `u8`:
   --> $DIR/specialization-polarity.rs:14:1
    |
 LL | impl<T> !Bar for T {}
-   | ------------------ first implementation here
+   | ------------------ negative implementation here
 LL | impl Bar for u8 {}
-   | ^^^^^^^^^^^^^^^ conflicting implementation for `u8`
+   | ^^^^^^^^^^^^^^^ positive implementation here
 
 error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/traits/negative-impls/negative-specializes-positive-item.rs b/src/test/ui/traits/negative-impls/negative-specializes-positive-item.rs
index 2ebf0bdcbe9..c7009430eae 100644
--- a/src/test/ui/traits/negative-impls/negative-specializes-positive-item.rs
+++ b/src/test/ui/traits/negative-impls/negative-specializes-positive-item.rs
@@ -6,8 +6,8 @@ trait MyTrait {
     fn foo();
 }
 impl<T> MyTrait for T {
-    default fn foo() { }
+    default fn foo() {}
 }
-impl !MyTrait for u32 { } //~ ERROR conflicting implementations
+impl !MyTrait for u32 {} //~ ERROR E0748
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/traits/negative-impls/negative-specializes-positive-item.stderr b/src/test/ui/traits/negative-impls/negative-specializes-positive-item.stderr
index 83421b4d7a1..21fd08251d4 100644
--- a/src/test/ui/traits/negative-impls/negative-specializes-positive-item.stderr
+++ b/src/test/ui/traits/negative-impls/negative-specializes-positive-item.stderr
@@ -1,12 +1,12 @@
-error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+error[E0748]: found both positive and negative implementation of trait `MyTrait` for type `u32`:
   --> $DIR/negative-specializes-positive-item.rs:11:1
    |
 LL | impl<T> MyTrait for T {
-   | --------------------- first implementation here
+   | --------------------- positive implementation here
 ...
-LL | impl !MyTrait for u32 { }
-   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+LL | impl !MyTrait for u32 {}
+   | ^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/traits/negative-impls/negative-specializes-positive.rs b/src/test/ui/traits/negative-impls/negative-specializes-positive.rs
index 7ab01612295..25301c696e1 100644
--- a/src/test/ui/traits/negative-impls/negative-specializes-positive.rs
+++ b/src/test/ui/traits/negative-impls/negative-specializes-positive.rs
@@ -2,13 +2,13 @@
 #![feature(optin_builtin_traits)]
 
 // Negative impl for u32 cannot "specialize" the base impl.
-trait MyTrait { }
-impl<T> MyTrait for T { }
-impl !MyTrait for u32 { } //~ ERROR conflicting implementations
+trait MyTrait {}
+impl<T> MyTrait for T {}
+impl !MyTrait for u32 {} //~ ERROR E0748
 
 // The second impl specializes the first, no error.
-trait MyTrait2 { }
-impl<T> MyTrait2 for T { }
-impl MyTrait2 for u32 { }
+trait MyTrait2 {}
+impl<T> MyTrait2 for T {}
+impl MyTrait2 for u32 {}
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/traits/negative-impls/negative-specializes-positive.stderr b/src/test/ui/traits/negative-impls/negative-specializes-positive.stderr
index a542e88673e..0e7426c8260 100644
--- a/src/test/ui/traits/negative-impls/negative-specializes-positive.stderr
+++ b/src/test/ui/traits/negative-impls/negative-specializes-positive.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+error[E0748]: found both positive and negative implementation of trait `MyTrait` for type `u32`:
   --> $DIR/negative-specializes-positive.rs:7:1
    |
-LL | impl<T> MyTrait for T { }
-   | --------------------- first implementation here
-LL | impl !MyTrait for u32 { }
-   | ^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+LL | impl<T> MyTrait for T {}
+   | --------------------- positive implementation here
+LL | impl !MyTrait for u32 {}
+   | ^^^^^^^^^^^^^^^^^^^^^ negative implementation here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.rs b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.rs
index 5c3e7fe3d01..d9c498fca66 100644
--- a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.rs
+++ b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.rs
@@ -4,13 +4,13 @@ use std::pin::Pin;
 
 struct MyType<'a>(Cell<Option<&'a mut MyType<'a>>>, PhantomPinned);
 
-impl<'a> Clone for &'a mut MyType<'a> { //~ ERROR conflicting implementations
+impl<'a> Clone for &'a mut MyType<'a> {
+    //~^ ERROR E0748
     fn clone(&self) -> &'a mut MyType<'a> {
         self.0.replace(None).unwrap()
     }
 }
 
-
 fn main() {
     let mut unpinned = MyType(Cell::new(None), PhantomPinned);
     let bad_addr = &unpinned as *const MyType<'_> as usize;
diff --git a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.stderr b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.stderr
index 1655d806fb4..f3305722cf2 100644
--- a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.stderr
+++ b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-clone.stderr
@@ -1,13 +1,11 @@
-error[E0119]: conflicting implementations of trait `std::clone::Clone` for type `&mut MyType<'_>`:
+error[E0748]: found both positive and negative implementation of trait `std::clone::Clone` for type `&mut MyType<'_>`:
   --> $DIR/pin-unsound-issue-66544-clone.rs:7:1
    |
 LL | impl<'a> Clone for &'a mut MyType<'a> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ positive implementation here
    |
-   = note: conflicting implementation in crate `core`:
-           - impl<T> std::clone::Clone for &mut T
-             where T: ?Sized;
+   = note: negative implementation in crate `core`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.rs b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.rs
index a34b8d635ab..cc27c301ffa 100644
--- a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.rs
+++ b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.rs
@@ -9,13 +9,13 @@ use std::pin::Pin;
 
 struct MyType<'a>(Cell<Option<&'a mut MyType<'a>>>, PhantomPinned);
 
-impl<'a> DerefMut for &'a MyType<'a> { //~ ERROR conflicting implementations
+impl<'a> DerefMut for &'a MyType<'a> {
+    //~^ ERROR E0748
     fn deref_mut(&mut self) -> &mut MyType<'a> {
         self.0.replace(None).unwrap()
     }
 }
 
-
 fn main() {
     let mut unpinned = MyType(Cell::new(None), PhantomPinned);
     let bad_addr = &unpinned as *const MyType<'_> as usize;
diff --git a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.stderr b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.stderr
index 80c9682a010..4e71c246824 100644
--- a/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.stderr
+++ b/src/test/ui/traits/negative-impls/pin-unsound-issue-66544-derefmut.stderr
@@ -1,13 +1,11 @@
-error[E0119]: conflicting implementations of trait `std::ops::DerefMut` for type `&MyType<'_>`:
+error[E0748]: found both positive and negative implementation of trait `std::ops::DerefMut` for type `&MyType<'_>`:
   --> $DIR/pin-unsound-issue-66544-derefmut.rs:12:1
    |
 LL | impl<'a> DerefMut for &'a MyType<'a> {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ positive implementation here
    |
-   = note: conflicting implementation in crate `core`:
-           - impl<T> std::ops::DerefMut for &T
-             where T: ?Sized;
+   = note: negative implementation in crate `core`
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.
diff --git a/src/test/ui/traits/negative-impls/positive-specializes-negative.rs b/src/test/ui/traits/negative-impls/positive-specializes-negative.rs
index 20267cf3aba..8a8ee70370f 100644
--- a/src/test/ui/traits/negative-impls/positive-specializes-negative.rs
+++ b/src/test/ui/traits/negative-impls/positive-specializes-negative.rs
@@ -1,9 +1,9 @@
 #![feature(specialization)]
 #![feature(optin_builtin_traits)]
 
-trait MyTrait { }
+trait MyTrait {}
 
-impl<T> !MyTrait for T { }
-impl MyTrait for u32 { } //~ ERROR conflicting implementations
+impl<T> !MyTrait for T {}
+impl MyTrait for u32 {} //~ ERROR E0748
 
-fn main() { }
+fn main() {}
diff --git a/src/test/ui/traits/negative-impls/positive-specializes-negative.stderr b/src/test/ui/traits/negative-impls/positive-specializes-negative.stderr
index 6e41759d2a2..ab371945a7e 100644
--- a/src/test/ui/traits/negative-impls/positive-specializes-negative.stderr
+++ b/src/test/ui/traits/negative-impls/positive-specializes-negative.stderr
@@ -1,11 +1,11 @@
-error[E0119]: conflicting implementations of trait `MyTrait` for type `u32`:
+error[E0748]: found both positive and negative implementation of trait `MyTrait` for type `u32`:
   --> $DIR/positive-specializes-negative.rs:7:1
    |
-LL | impl<T> !MyTrait for T { }
-   | ---------------------- first implementation here
-LL | impl MyTrait for u32 { }
-   | ^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `u32`
+LL | impl<T> !MyTrait for T {}
+   | ---------------------- negative implementation here
+LL | impl MyTrait for u32 {}
+   | ^^^^^^^^^^^^^^^^^^^^ positive implementation here
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0119`.
+For more information about this error, try `rustc --explain E0748`.