Move /src/test to /tests

tests/ui/functions-closures/nullable-pointer-opt-closures.rs

@@ -0,0 +1,34 @@
+// run-pass
+
+use std::mem;
+
+pub fn main() {
+    // By Ref Capture
+    let a = 10i32;
+    let b = Some(|| println!("{}", a));
+    // When we capture by reference we can use any of the
+    // captures as the discriminant since they're all
+    // behind a pointer.
+    assert_eq!(mem::size_of_val(&b), mem::size_of::<usize>());
+
+    // By Value Capture
+    let a = Box::new(12i32);
+    let b = Some(move || println!("{}", a));
+    // We captured `a` by value and since it's a `Box` we can use it
+    // as the discriminant.
+    assert_eq!(mem::size_of_val(&b), mem::size_of::<Box<i32>>());
+
+    // By Value Capture - Transitive case
+    let a = "Hello".to_string(); // String -> Vec -> Unique -> NonZero
+    let b = Some(move || println!("{}", a));
+    // We captured `a` by value and since down the chain it contains
+    // a `NonZero` field, we can use it as the discriminant.
+    assert_eq!(mem::size_of_val(&b), mem::size_of::<String>());
+
+    // By Value - No Optimization
+    let a = 14i32;
+    let b = Some(move || println!("{}", a));
+    // We captured `a` by value but we can't use it as the discriminant
+    // thus we end up with an extra field for the discriminant
+    assert_eq!(mem::size_of_val(&b), mem::size_of::<(i32, i32)>());
+}