4 files changed, 42 insertions, 0 deletions
diff --git a/src/test/ui/dyn-star/auxiliary/dyn-star-foreign.rs b/src/test/ui/dyn-star/auxiliary/dyn-star-foreign.rs
new file mode 100644
index 00000000000..7673c793678
--- /dev/null
+++ b/src/test/ui/dyn-star/auxiliary/dyn-star-foreign.rs
@@ -0,0 +1,10 @@
+#![feature(dyn_star)]
+#![allow(incomplete_features)]
+
+use std::fmt::Display;
+
+pub fn require_dyn_star_display(_: dyn* Display) {}
+
+fn works_locally() {
+    require_dyn_star_display(1usize);
+}
diff --git a/src/test/ui/dyn-star/make-dyn-star.rs b/src/test/ui/dyn-star/make-dyn-star.rs
index 4f9393abb30..e5255a64ba1 100644
--- a/src/test/ui/dyn-star/make-dyn-star.rs
+++ b/src/test/ui/dyn-star/make-dyn-star.rs
@@ -8,6 +8,11 @@ fn make_dyn_star(i: usize) {
     let _dyn_i: dyn* Debug = i;
 }
 
+fn make_dyn_star_explicit(i: usize) {
+    let _dyn_i: dyn* Debug = i as dyn* Debug;
+}
+
 fn main() {
     make_dyn_star(42);
+    make_dyn_star_explicit(42);
 }
diff --git a/src/test/ui/dyn-star/no-implicit-dyn-star.rs b/src/test/ui/dyn-star/no-implicit-dyn-star.rs
new file mode 100644
index 00000000000..d9470e28417
--- /dev/null
+++ b/src/test/ui/dyn-star/no-implicit-dyn-star.rs
@@ -0,0 +1,8 @@
+// aux-build:dyn-star-foreign.rs
+
+extern crate dyn_star_foreign;
+
+fn main() {
+    dyn_star_foreign::require_dyn_star_display(1usize);
+    //~^ ERROR mismatched types
+}
diff --git a/src/test/ui/dyn-star/no-implicit-dyn-star.stderr b/src/test/ui/dyn-star/no-implicit-dyn-star.stderr
new file mode 100644
index 00000000000..e7c5918629b
--- /dev/null
+++ b/src/test/ui/dyn-star/no-implicit-dyn-star.stderr
@@ -0,0 +1,19 @@
+error[E0308]: mismatched types
+  --> $DIR/no-implicit-dyn-star.rs:6:48
+   |
+LL |     dyn_star_foreign::require_dyn_star_display(1usize);
+   |     ------------------------------------------ ^^^^^^ expected trait object `dyn std::fmt::Display`, found `usize`
+   |     |
+   |     arguments to this function are incorrect
+   |
+   = note: expected trait object `(dyn* std::fmt::Display + 'static)`
+                      found type `usize`
+note: function defined here
+  --> $DIR/auxiliary/dyn-star-foreign.rs:6:8
+   |
+LL | pub fn require_dyn_star_display(_: dyn* Display) {}
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.