1 files changed, 32 insertions, 0 deletions
diff --git a/src/test/ui/imports/extern-crate-used.rs b/src/test/ui/imports/extern-crate-used.rs
new file mode 100644
index 000000000..8198c1816
--- /dev/null
+++ b/src/test/ui/imports/extern-crate-used.rs
@@ -0,0 +1,32 @@
+// Extern crate items are marked as used if they are used
+// through extern prelude entries introduced by them.
+
+// edition:2018
+
+#![deny(unused_extern_crates)]
+
+// Shouldn't suggest changing to `use`, as new name
+// would no longer be added to the prelude which could cause
+// compilation errors for imports that use the new name in
+// other modules. See #57672.
+extern crate core as iso1;
+extern crate core as iso2;
+extern crate core as iso3;
+extern crate core as iso4;
+
+// Doesn't introduce its extern prelude entry, so it's still considered unused.
+extern crate core; //~ ERROR unused extern crate
+
+mod m {
+    use iso1::any as are_you_okay1;
+    use ::iso2::any as are_you_okay2;
+    type AreYouOkay1 = dyn iso3::any::Any;
+    type AreYouOkay2 = dyn (::iso4::any::Any);
+
+    use core::any as are_you_okay3;
+    use ::core::any as are_you_okay4;
+    type AreYouOkay3 = dyn core::any::Any;
+    type AreYouOkay4 = dyn (::core::any::Any);
+}
+
+fn main() {}