fn pointers don't implement Fn/FnMut/FnOnce traits if its return type is unsized

1 files changed, 14 insertions, 0 deletions

diff --git a/src/test/ui/function-pointer/unsized-ret.rs b/src/test/ui/function-pointer/unsized-ret.rs
new file mode 100644
index 00000000000..60af5769d6d
--- /dev/null
+++ b/src/test/ui/function-pointer/unsized-ret.rs
@@ -0,0 +1,14 @@
+#![feature(fn_traits)]
+#![feature(unboxed_closures)]
+
+fn foo<F: Fn<T>, T>(f: Option<F>, t: T) {
+    let y = (f.unwrap()).call(t);
+}
+
+fn main() {
+    foo::<fn() -> str, _>(None, ());
+    //~^ ERROR the size for values of type `str` cannot be known at compilation time
+
+    foo::<for<'a> fn(&'a ()) -> (dyn std::fmt::Display + 'a), _>(None, (&(),));
+    //~^ ERROR the size for values of type `(dyn std::fmt::Display + 'a)` cannot be known at compilation time
+}