1 files changed, 10 insertions, 0 deletions
diff --git a/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.rs b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.rs
new file mode 100644
index 000000000..3ce721618
--- /dev/null
+++ b/src/test/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.rs
@@ -0,0 +1,10 @@
+// Variation on `borrowck-use-uninitialized-in-cast` in which we do a
+// trait cast from an uninitialized source. Issue #20791.
+
+trait Foo { fn dummy(&self) { } }
+impl Foo for i32 { }
+
+fn main() {
+    let x: &i32;
+    let y = x as *const dyn Foo; //~ ERROR [E0381]
+}