1 files changed, 36 insertions, 0 deletions
diff --git a/tests/ui/traits/suggest-where-clause.rs b/tests/ui/traits/suggest-where-clause.rs
new file mode 100644
index 00000000000..46d047a2de3
--- /dev/null
+++ b/tests/ui/traits/suggest-where-clause.rs
@@ -0,0 +1,36 @@
+use std::mem;
+
+struct Misc<T:?Sized>(T);
+
+fn check<T: Iterator, U: ?Sized>() {
+    // suggest a where-clause, if needed
+    mem::size_of::<U>();
+    //~^ ERROR the size for values of type
+
+    mem::size_of::<Misc<U>>();
+    //~^ ERROR the size for values of type
+
+    // ... even if T occurs as a type parameter
+
+    <u64 as From<T>>::from;
+    //~^ ERROR `u64: From<T>` is not satisfied
+
+    <u64 as From<<T as Iterator>::Item>>::from;
+    //~^ ERROR `u64: From<<T as Iterator>::Item>` is not satisfied
+
+    // ... but not if there are inference variables
+
+    <Misc<_> as From<T>>::from;
+    //~^ ERROR `Misc<_>: From<T>` is not satisfied
+
+    // ... and also not if the error is not related to the type
+
+    mem::size_of::<[T]>();
+    //~^ ERROR the size for values of type
+
+    mem::size_of::<[&U]>();
+    //~^ ERROR the size for values of type
+}
+
+fn main() {
+}