Auto merge of #106358 - TroyNeubauer:improve-foreign-orphan-error, r=estebank

Implement fix for #67535

Implements a fix for #67535
r? `@estebank`

3 files changed, 62 insertions, 1 deletions

diff --git a/src/test/ui/issues/issue-67535.rs b/src/test/ui/issues/issue-67535.rs
new file mode 100644
index 00000000000..24f50621310
--- /dev/null
+++ b/src/test/ui/issues/issue-67535.rs
@@ -0,0 +1,22 @@
+fn main() {}
+
+impl std::ops::AddAssign for () {
+    //~^ ERROR only traits defined in the current crate can be implemented for arbitrary types
+    fn add_assign(&self, other: ()) -> () {
+        ()
+    }
+}
+
+impl std::ops::AddAssign for [(); 1] {
+    //~^ ERROR only traits defined in the current crate can be implemented for arbitrary types
+    fn add_assign(&self, other: [(); 1]) -> [(); 1] {
+        [()]
+    }
+}
+
+impl std::ops::AddAssign for &[u8] {
+    //~^ ERROR only traits defined in the current crate can be implemented for arbitrary types
+    fn add_assign(&self, other: &[u8]) -> &[u8] {
+        self
+    }
+}
diff --git a/src/test/ui/issues/issue-67535.stderr b/src/test/ui/issues/issue-67535.stderr
new file mode 100644
index 00000000000..4d7a02a5096
--- /dev/null
+++ b/src/test/ui/issues/issue-67535.stderr
@@ -0,0 +1,39 @@
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/issue-67535.rs:3:1
+   |
+LL | impl std::ops::AddAssign for () {
+   | ^^^^^-------------------^^^^^--
+   | |    |                       |
+   | |    |                       this is not defined in the current crate because tuples are always foreign
+   | |    this is not defined in the current crate because this is a foreign trait
+   | impl doesn't use only types from inside the current crate
+   |
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/issue-67535.rs:10:1
+   |
+LL | impl std::ops::AddAssign for [(); 1] {
+   | ^^^^^-------------------^^^^^-------
+   | |    |                       |
+   | |    |                       this is not defined in the current crate because arrays are always foreign
+   | |    this is not defined in the current crate because this is a foreign trait
+   | impl doesn't use only types from inside the current crate
+   |
+   = note: define and implement a trait or new type instead
+
+error[E0117]: only traits defined in the current crate can be implemented for arbitrary types
+  --> $DIR/issue-67535.rs:17:1
+   |
+LL | impl std::ops::AddAssign for &[u8] {
+   | ^^^^^-------------------^^^^^-----
+   | |    |                       |
+   | |    |                       this is not defined in the current crate because slices are always foreign
+   | |    this is not defined in the current crate because this is a foreign trait
+   | impl doesn't use only types from inside the current crate
+   |
+   = note: define and implement a trait or new type instead
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0117`.
diff --git a/src/tools/tidy/src/ui_tests.rs b/src/tools/tidy/src/ui_tests.rs
index f746bdeffd7..070e72437be 100644
--- a/src/tools/tidy/src/ui_tests.rs
+++ b/src/tools/tidy/src/ui_tests.rs
@@ -10,7 +10,7 @@ use std::path::Path;
 const ENTRY_LIMIT: usize = 1000;
 // FIXME: The following limits should be reduced eventually.
 const ROOT_ENTRY_LIMIT: usize = 939;
-const ISSUES_ENTRY_LIMIT: usize = 2020;
+const ISSUES_ENTRY_LIMIT: usize = 2050;
 
 fn check_entries(path: &Path, bad: &mut bool) {
     for dir in Walk::new(&path.join("test/ui")) {