1 files changed, 38 insertions, 0 deletions
diff --git a/tests/ui/traits/copy-guessing.rs b/tests/ui/traits/copy-guessing.rs
new file mode 100644
index 00000000000..f031dd9ca48
--- /dev/null
+++ b/tests/ui/traits/copy-guessing.rs
@@ -0,0 +1,38 @@
+// run-pass
+#![allow(dead_code)]
+// "guessing" in trait selection can affect `copy_or_move`. Check that this
+// is correctly handled. I am not sure what is the "correct" behaviour,
+// but we should at least not ICE.
+
+use std::mem;
+
+struct U([u8; 1337]);
+
+struct S<'a,T:'a>(&'a T);
+impl<'a, T> Clone for S<'a, T> { fn clone(&self) -> Self { S(self.0) } }
+/// This impl triggers inference "guessing" - S<_>: Copy => _ = U
+impl<'a> Copy for S<'a, Option<U>> {}
+
+fn assert_impls_fn<R,T: Fn()->R>(_: &T){}
+
+fn main() {
+    let n = None;
+    let e = S(&n);
+    let f = || {
+        // S being copy is critical for this to work
+        drop(e);
+        mem::size_of_val(e.0)
+    };
+    assert_impls_fn(&f);
+    assert_eq!(f(), 1337+1);
+
+    assert_eq!((|| {
+        // S being Copy is not critical here, but
+        // we check it anyway.
+        let n = None;
+        let e = S(&n);
+        let ret = mem::size_of_val(e.0);
+        drop(e);
+        ret
+    })(), 1337+1);
+}