nullable-pointer-iotareduction

Author: Kivooeo

tests/ui/layout/nullable-pointer-optimization.rs

@@ -1,27 +1,34 @@
-//@ run-pass
+//! Nullable pointer optimization with iota-reduction for enums.
+//!
+//! Iota-reduction is a rule from the Calculus of (Co-)Inductive Constructions:
+//! "a destructor applied to an object built from a constructor behaves as expected".
+//! See <https://coq.inria.fr/doc/language/core/conversion.html#iota-reduction>.
+//!
+//! This test verifies that nullable pointer optimization works correctly for both
+//! Option<T> and custom enums, accounting for pointers and regions.
 
-// Iota-reduction is a rule in the Calculus of (Co-)Inductive Constructions,
-// which "says that a destructor applied to an object built from a constructor
-// behaves as expected".  -- https://coq.inria.fr/doc/language/core/conversion.html#iota-reduction
-//
-// It's a little more complicated here, because of pointers and regions and
-// trying to get assert failure messages that at least identify which case
-// failed.
+//@ run-pass
 
 #![allow(unpredictable_function_pointer_comparisons)]
 
-enum E<T> { Thing(isize, T), #[allow(dead_code)] Nothing((), ((), ()), [i8; 0]) }
+enum E<T> {
+    Thing(isize, T),
+    #[allow(dead_code)]
+    Nothing((), ((), ()), [i8; 0]),
+}
+
 impl<T> E<T> {
     fn is_none(&self) -> bool {
         match *self {
             E::Thing(..) => false,
-            E::Nothing(..) => true
+            E::Nothing(..) => true,
         }
     }
+
     fn get_ref(&self) -> (isize, &T) {
         match *self {
-            E::Nothing(..) => panic!("E::get_ref(Nothing::<{}>)",  stringify!(T)),
-            E::Thing(x, ref y) => (x, y)
+            E::Nothing(..) => panic!("E::get_ref(Nothing::<{}>)", stringify!(T)),
+            E::Thing(x, ref y) => (x, y),
         }
     }
 }
@@ -36,7 +43,7 @@ macro_rules! check_option {
         let s_ = Some::<$T>(e);
         let $v = s_.as_ref().unwrap();
         $chk
-    }}
+    }};
 }
 
 macro_rules! check_fancy {
@@ -48,11 +55,10 @@ macro_rules! check_fancy {
         let e = $e;
         let t_ = E::Thing::<$T>(23, e);
         match t_.get_ref() {
-            (23, $v) => { $chk }
-            _ => panic!("Thing::<{}>(23, {}).get_ref() != (23, _)",
-                       stringify!($T), stringify!($e))
+            (23, $v) => $chk,
+            _ => panic!("Thing::<{}>(23, {}).get_ref() != (23, _)", stringify!($T), stringify!($e)),
         }
-    }}
+    }};
 }
 
 macro_rules! check_type {
@@ -67,7 +73,5 @@ pub fn main() {
     check_type!(Box::new(18), Box<isize>);
     check_type!("foo".to_string(), String);
     check_type!(vec![20, 22], Vec<isize>);
-    check_type!(main, fn(), |pthing| {
-        assert_eq!(main as fn(), *pthing as fn())
-    });
+    check_type!(main, fn(), |pthing| assert_eq!(main as fn(), *pthing as fn()));
 }