Rollup merge of #66253 - ohadravid:improve-errors-after-re-rebalance-coherence, r=estebank

Improve errors after re rebalance coherence

Following #65247, I noticed that some error messages should be updated to reflect the changes of `re_rebalance_coherence` (also there was a [note](https://rust-lang.github.io/rfcs/2451-re-rebalancing-coherence.html#teaching-users) in the RFC about it).

First, error message `E0210` was updated to match the RFC, and I also tried to improve a little the error when the "order" of types is problematic.

For code like this:
```
#![feature(re_rebalance_coherence)] // Now stable

struct Wrap<T>(T);

impl<T> From<Wrap<T>> for T {
    fn from(x: Wrap<T>) -> T {
        x.0
    }
}
```

The old error was:
```
error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
 --> src/lib.rs:5:6
  |
5 | impl<T> From<Wrap<T>> for T {
  |      ^ type parameter `T` must be used as the type parameter for some local type
  |
  = note: only traits defined in the current crate can be implemented for a type parameter

```

and the new error is:
```
error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Wrap<T>`)
  --> main.rs:66:6
   |
66 | impl<T> From<Wrap<T>> for T {
   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Wrap<T>`)
   |
   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
```

I tried to point at the uncovered `T`, but couldn't get something which was reliable (but I'll be happy to try if someone points me in the right direction).

r? @estebank
cc @nikomatsakis

Fixes #65247

22 files changed, 49 insertions, 23 deletions

diff --git a/src/test/ui/coherence/coherence-all-remote.stderr b/src/test/ui/coherence/coherence-all-remote.stderr
index b35ae46f888..6ecfb2c5eb0 100644
--- a/src/test/ui/coherence/coherence-all-remote.stderr
+++ b/src/test/ui/coherence/coherence-all-remote.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<T> for isize { }
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/coherence/coherence-bigint-param.stderr b/src/test/ui/coherence/coherence-bigint-param.stderr
index bb81d7adea2..d431c5f4b52 100644
--- a/src/test/ui/coherence/coherence-bigint-param.stderr
+++ b/src/test/ui/coherence/coherence-bigint-param.stderr
@@ -1,10 +1,11 @@
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`BigInt`)
   --> $DIR/coherence-bigint-param.rs:8:6
    |
 LL | impl<T> Remote1<BigInt> for T { }
-   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`BigInt`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/coherence-cross-crate-conflict.stderr b/src/test/ui/coherence/coherence-cross-crate-conflict.stderr
index cb66f9b0c7f..c00751a0f23 100644
--- a/src/test/ui/coherence/coherence-cross-crate-conflict.stderr
+++ b/src/test/ui/coherence/coherence-cross-crate-conflict.stderr
@@ -13,6 +13,7 @@ error[E0210]: type parameter `A` must be used as the type parameter for some loc
 LL | impl<A> Foo for A {
    |      ^ type parameter `A` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/coherence-lone-type-parameter.stderr b/src/test/ui/coherence/coherence-lone-type-parameter.stderr
index 3791d96302b..2c3b4fc3ad2 100644
--- a/src/test/ui/coherence/coherence-lone-type-parameter.stderr
+++ b/src/test/ui/coherence/coherence-lone-type-parameter.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote for T { }
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/coherence/impl[t]-foreign-for-fundamental[t].stderr b/src/test/ui/coherence/impl[t]-foreign-for-fundamental[t].stderr
index 69194bdaf56..8a951d407ca 100644
--- a/src/test/ui/coherence/impl[t]-foreign-for-fundamental[t].stderr
+++ b/src/test/ui/coherence/impl[t]-foreign-for-fundamental[t].stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote for Box<T> {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/coherence/impl[t]-foreign[foreign]-for-fundamental[t].stderr b/src/test/ui/coherence/impl[t]-foreign[foreign]-for-fundamental[t].stderr
index b0f34419bb3..c5759244eff 100644
--- a/src/test/ui/coherence/impl[t]-foreign[foreign]-for-fundamental[t].stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[foreign]-for-fundamental[t].stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<u32> for Box<T> {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
@@ -12,6 +13,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<'a, T> Remote1<u32> for &'a T {
    |          ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/impl[t]-foreign[foreign]-for-t.stderr b/src/test/ui/coherence/impl[t]-foreign[foreign]-for-t.stderr
index 002f8b7286a..e8663fd7d82 100644
--- a/src/test/ui/coherence/impl[t]-foreign[foreign]-for-t.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[foreign]-for-t.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<u32> for T {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-foreign.stderr b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-foreign.stderr
index 0c43936e6d4..639bee2b8ec 100644
--- a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-foreign.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-foreign.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<Box<T>> for u32 {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
@@ -12,6 +13,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<'a, T> Remote1<&'a T> for u32 {
    |          ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-fundamental[t].stderr b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-fundamental[t].stderr
index f81f15b204b..0b6c81b53cd 100644
--- a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-fundamental[t].stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-fundamental[t].stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<'a, T> Remote1<Box<T>> for &'a T {
    |          ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
@@ -12,6 +13,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<'a, T> Remote1<&'a T> for Box<T> {
    |          ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-t.stderr b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-t.stderr
index 24fd492c57c..fe40490822e 100644
--- a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-t.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]]-for-t.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<Box<T>> for T {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
@@ -12,6 +13,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<'a, T> Remote1<&'a T> for T {
    |          ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs
index 4666e449ca9..c9e3594cd34 100644
--- a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs
+++ b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs
@@ -8,11 +8,11 @@ use std::rc::Rc;
 struct Local;
 
 impl<T> Remote2<Box<T>, Local> for u32 {
-    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+    //~^ ERROR type parameter `T` must be covered by another type
 }
 
 impl<'a, T> Remote2<&'a T, Local> for u32 {
-    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+    //~^ ERROR type parameter `T` must be covered by another type
 }
 
 fn main() {}
diff --git a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.stderr b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.stderr
index 6a1db165416..1eaef59b3f8 100644
--- a/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[fundamental[t]_local]-for-foreign.stderr
@@ -1,18 +1,20 @@
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
   --> $DIR/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs:10:6
    |
 LL | impl<T> Remote2<Box<T>, Local> for u32 {
-   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
   --> $DIR/impl[t]-foreign[fundamental[t]_local]-for-foreign.rs:14:10
    |
 LL | impl<'a, T> Remote2<&'a T, Local> for u32 {
-   |          ^ type parameter `T` must be used as the type parameter for some local type
+   |          ^ type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].rs b/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].rs
index db88c330b39..7709bd9c89b 100644
--- a/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].rs
+++ b/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].rs
@@ -8,11 +8,11 @@ use std::rc::Rc;
 struct Local;
 
 impl<T> Remote1<Local> for Box<T> {
-    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+    //~^ ERROR type parameter `T` must be covered by another type
 }
 
 impl<T> Remote1<Local> for &T {
-    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+    //~^ ERROR type parameter `T` must be covered by another type
 }
 
 fn main() {}
diff --git a/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].stderr b/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].stderr
index b5fdb16c2f3..4d39186d494 100644
--- a/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[local]-for-fundamental[t].stderr
@@ -1,18 +1,20 @@
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
   --> $DIR/impl[t]-foreign[local]-for-fundamental[t].rs:10:6
    |
 LL | impl<T> Remote1<Local> for Box<T> {
-   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
   --> $DIR/impl[t]-foreign[local]-for-fundamental[t].rs:14:6
    |
 LL | impl<T> Remote1<Local> for &T {
-   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/coherence/impl[t]-foreign[local]-for-t.rs b/src/test/ui/coherence/impl[t]-foreign[local]-for-t.rs
index dd4110d31e6..eed3a4b5c23 100644
--- a/src/test/ui/coherence/impl[t]-foreign[local]-for-t.rs
+++ b/src/test/ui/coherence/impl[t]-foreign[local]-for-t.rs
@@ -8,7 +8,7 @@ use std::rc::Rc;
 struct Local;
 
 impl<T> Remote1<Local> for T {
-    //~^ ERROR type parameter `T` must be used as the type parameter for some local type
+    //~^ ERROR type parameter `T` must be covered by another type
 }
 
 fn main() {}
diff --git a/src/test/ui/coherence/impl[t]-foreign[local]-for-t.stderr b/src/test/ui/coherence/impl[t]-foreign[local]-for-t.stderr
index 7b65212f62a..d74be4cec72 100644
--- a/src/test/ui/coherence/impl[t]-foreign[local]-for-t.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[local]-for-t.stderr
@@ -1,10 +1,11 @@
-error[E0210]: type parameter `T` must be used as the type parameter for some local type (e.g., `MyStruct<T>`)
+error[E0210]: type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
   --> $DIR/impl[t]-foreign[local]-for-t.rs:10:6
    |
 LL | impl<T> Remote1<Local> for T {
-   |      ^ type parameter `T` must be used as the type parameter for some local type
+   |      ^ type parameter `T` must be covered by another type when it appears before the first local type (`Local`)
    |
-   = note: only traits defined in the current crate can be implemented for a type parameter
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local, and no uncovered type parameters appear before that first local type
+   = note: in this case, 'before' refers to the following order: `impl<..> ForeignTrait<T1, ..., Tn> for T0`, where `T0` is the first and `Tn` is the last
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/coherence/impl[t]-foreign[t]-for-foreign.stderr b/src/test/ui/coherence/impl[t]-foreign[t]-for-foreign.stderr
index 2e5ae6a8eb3..b26feb4914c 100644
--- a/src/test/ui/coherence/impl[t]-foreign[t]-for-foreign.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[t]-for-foreign.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<T> for u32 {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/coherence/impl[t]-foreign[t]-for-fundamental.stderr b/src/test/ui/coherence/impl[t]-foreign[t]-for-fundamental.stderr
index 3976f06947f..5e8cc552c98 100644
--- a/src/test/ui/coherence/impl[t]-foreign[t]-for-fundamental.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[t]-for-fundamental.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<T> for Box<T> {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error[E0210]: type parameter `B` must be used as the type parameter for some local type (e.g., `MyStruct<B>`)
@@ -12,6 +13,7 @@ error[E0210]: type parameter `B` must be used as the type parameter for some loc
 LL | impl<'a, A, B> Remote1<A> for &'a B {
    |             ^ type parameter `B` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/coherence/impl[t]-foreign[t]-for-t.stderr b/src/test/ui/coherence/impl[t]-foreign[t]-for-t.stderr
index 8d858b8abee..d3226d33bee 100644
--- a/src/test/ui/coherence/impl[t]-foreign[t]-for-t.stderr
+++ b/src/test/ui/coherence/impl[t]-foreign[t]-for-t.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Remote1<T> for T {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error
diff --git a/src/test/ui/error-codes/e0119/issue-28981.stderr b/src/test/ui/error-codes/e0119/issue-28981.stderr
index ec8e8144d42..2a78cc8b2db 100644
--- a/src/test/ui/error-codes/e0119/issue-28981.stderr
+++ b/src/test/ui/error-codes/e0119/issue-28981.stderr
@@ -14,6 +14,7 @@ error[E0210]: type parameter `Foo` must be used as the type parameter for some l
 LL | impl<Foo> Deref for Foo { }
    |      ^^^ type parameter `Foo` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 2 previous errors
diff --git a/src/test/ui/issues/issue-41974.stderr b/src/test/ui/issues/issue-41974.stderr
index 12d4da71599..9f164822dea 100644
--- a/src/test/ui/issues/issue-41974.stderr
+++ b/src/test/ui/issues/issue-41974.stderr
@@ -21,6 +21,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> Drop for T where T: A {
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to 3 previous errors
diff --git a/src/test/ui/orphan-check-diagnostics.stderr b/src/test/ui/orphan-check-diagnostics.stderr
index cb21b26bba7..c84d401898c 100644
--- a/src/test/ui/orphan-check-diagnostics.stderr
+++ b/src/test/ui/orphan-check-diagnostics.stderr
@@ -4,6 +4,7 @@ error[E0210]: type parameter `T` must be used as the type parameter for some loc
 LL | impl<T> RemoteTrait for T where T: LocalTrait {}
    |      ^ type parameter `T` must be used as the type parameter for some local type
    |
+   = note: implementing a foreign trait is only possible if at least one of the types for which is it implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter
 
 error: aborting due to previous error