4 files changed, 33 insertions, 0 deletions
diff --git a/tests/ui/tool-attributes/auxiliary/p1.rs b/tests/ui/tool-attributes/auxiliary/p1.rs
new file mode 100644
index 000000000..47195c7e9
--- /dev/null
+++ b/tests/ui/tool-attributes/auxiliary/p1.rs
@@ -0,0 +1,3 @@
+#![feature(rustc_attrs)]
+#[rustc_diagnostic_item = "Foo"]
+pub struct Foo {}
diff --git a/tests/ui/tool-attributes/auxiliary/p2.rs b/tests/ui/tool-attributes/auxiliary/p2.rs
new file mode 100644
index 000000000..47195c7e9
--- /dev/null
+++ b/tests/ui/tool-attributes/auxiliary/p2.rs
@@ -0,0 +1,3 @@
+#![feature(rustc_attrs)]
+#[rustc_diagnostic_item = "Foo"]
+pub struct Foo {}
diff --git a/tests/ui/tool-attributes/duplicate-diagnostic.rs b/tests/ui/tool-attributes/duplicate-diagnostic.rs
new file mode 100644
index 000000000..e2cf95087
--- /dev/null
+++ b/tests/ui/tool-attributes/duplicate-diagnostic.rs
@@ -0,0 +1,13 @@
+// aux-build: p1.rs
+// aux-build: p2.rs
+
+// error-pattern: duplicate diagnostic item in crate `p2`
+// error-pattern: note: the diagnostic item is first defined in crate `p1`
+
+#![feature(rustc_attrs)]
+extern crate p1;
+extern crate p2;
+
+#[rustc_diagnostic_item = "Foo"]
+pub struct Foo {} //~ ERROR duplicate diagnostic item in crate `duplicate_diagnostic`: `Foo`
+fn main() {}
diff --git a/tests/ui/tool-attributes/duplicate-diagnostic.stderr b/tests/ui/tool-attributes/duplicate-diagnostic.stderr
new file mode 100644
index 000000000..26bd6a82e
--- /dev/null
+++ b/tests/ui/tool-attributes/duplicate-diagnostic.stderr
@@ -0,0 +1,14 @@
+error: duplicate diagnostic item in crate `p2`: `Foo`.
+   |
+   = note: the diagnostic item is first defined in crate `p1`.
+
+error: duplicate diagnostic item in crate `duplicate_diagnostic`: `Foo`.
+  --> $DIR/duplicate-diagnostic.rs:12:1
+   |
+LL | pub struct Foo {}
+   | ^^^^^^^^^^^^^^
+   |
+   = note: the diagnostic item is first defined in crate `p2`.
+
+error: aborting due to 2 previous errors
+