add some sanity tests

tests/run-pass/function_pointers.rs

@@ -2,6 +2,10 @@ fn f() -> i32 {
     42
 }
 
+fn g(i: i32) -> i32 {
+    i*42
+}
+
 fn return_fn_ptr() -> fn() -> i32 {
     f
 }
@@ -10,8 +14,22 @@ fn call_fn_ptr() -> i32 {
     return_fn_ptr()()
 }
 
+fn indirect<F: Fn() -> i32>(f: F) -> i32 { f() }
+fn indirect_mut<F: FnMut() -> i32>(mut f: F) -> i32 { f() }
+fn indirect_once<F: FnOnce() -> i32>(f: F) -> i32 { f() }
+
+fn indirect2<F: Fn(i32) -> i32>(f: F) -> i32 { f(10) }
+fn indirect_mut2<F: FnMut(i32) -> i32>(mut f: F) -> i32 { f(10) }
+fn indirect_once2<F: FnOnce(i32) -> i32>(f: F) -> i32 { f(10) }
+
 fn main() {
     assert_eq!(call_fn_ptr(), 42);
+    assert_eq!(indirect(f), 42);
+    assert_eq!(indirect_mut(f), 42);
+    assert_eq!(indirect_once(f), 42);
+    assert_eq!(indirect2(g), 420);
+    assert_eq!(indirect_mut2(g), 420);
+    assert_eq!(indirect_once2(g), 420);
     assert!(return_fn_ptr() == f);
     assert!(return_fn_ptr() as unsafe fn() -> i32 == f as fn() -> i32 as unsafe fn() -> i32);
 }