2 files changed, 38 insertions, 0 deletions
diff --git a/src/test/ui/extern/extern-type-diag-not-similar.rs b/src/test/ui/extern/extern-type-diag-not-similar.rs
new file mode 100644
index 00000000000..39d00a6c1bc
--- /dev/null
+++ b/src/test/ui/extern/extern-type-diag-not-similar.rs
@@ -0,0 +1,22 @@
+// We previously mentioned other extern types in the error message here.
+//
+// Two extern types shouldn't really be considered similar just
+// because they are both extern types.
+
+#![feature(extern_types)]
+extern {
+    type ShouldNotBeMentioned;
+}
+
+extern {
+    type Foo;
+}
+
+unsafe impl Send for ShouldNotBeMentioned {}
+
+fn assert_send<T: Send + ?Sized>() {}
+
+fn main() {
+    assert_send::<Foo>()
+    //~^ ERROR `Foo` cannot be sent between threads safely
+}
diff --git a/src/test/ui/extern/extern-type-diag-not-similar.stderr b/src/test/ui/extern/extern-type-diag-not-similar.stderr
new file mode 100644
index 00000000000..75836f7eca1
--- /dev/null
+++ b/src/test/ui/extern/extern-type-diag-not-similar.stderr
@@ -0,0 +1,16 @@
+error[E0277]: `Foo` cannot be sent between threads safely
+  --> $DIR/extern-type-diag-not-similar.rs:20:19
+   |
+LL |     assert_send::<Foo>()
+   |                   ^^^ `Foo` cannot be sent between threads safely
+   |
+   = help: the trait `Send` is not implemented for `Foo`
+note: required by a bound in `assert_send`
+  --> $DIR/extern-type-diag-not-similar.rs:17:19
+   |
+LL | fn assert_send<T: Send + ?Sized>() {}
+   |                   ^^^^ required by this bound in `assert_send`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0277`.