2 #![feature(transparent_unions)]
5 use std::num::NonZeroUsize;
10 trait Trait { fn dummy(&self) { } }
11 trait Mirror { type Image; }
12 impl<T> Mirror for T { type Image = T; }
13 struct ParamTypeStruct<T>(T);
14 struct AssocTypeStruct<T>(<T as Mirror>::Image);
16 union MaybeUninitUnion<T: Copy> {
23 assert_eq!(size_of::<fn(isize)>(), size_of::<Option<fn(isize)>>());
24 assert_eq!(size_of::<extern "C" fn(isize)>(), size_of::<Option<extern "C" fn(isize)>>());
26 // Slices - &str / &[T] / &mut [T]
27 assert_eq!(size_of::<&str>(), size_of::<Option<&str>>());
28 assert_eq!(size_of::<&[isize]>(), size_of::<Option<&[isize]>>());
29 assert_eq!(size_of::<&mut [isize]>(), size_of::<Option<&mut [isize]>>());
31 // Traits - Box<Trait> / &Trait / &mut Trait
32 assert_eq!(size_of::<Box<dyn Trait>>(), size_of::<Option<Box<dyn Trait>>>());
33 assert_eq!(size_of::<&dyn Trait>(), size_of::<Option<&dyn Trait>>());
34 assert_eq!(size_of::<&mut dyn Trait>(), size_of::<Option<&mut dyn Trait>>());
37 assert_eq!(size_of::<Box<isize>>(), size_of::<Option<Box<isize>>>());
39 // The optimization can't apply to raw pointers or unions with a ZST field.
40 assert!(size_of::<Option<*const isize>>() != size_of::<*const isize>());
41 assert!(Some(0 as *const isize).is_some()); // Can't collapse None to null
42 assert_ne!(size_of::<fn(isize)>(), size_of::<Option<MaybeUninitUnion<fn(isize)>>>());
43 assert_ne!(size_of::<&str>(), size_of::<Option<MaybeUninitUnion<&str>>>());
44 assert_ne!(size_of::<NonNull<isize>>(), size_of::<Option<MaybeUninitUnion<NonNull<isize>>>>());
49 struct Bar(Box<isize>);
51 // Should apply through structs
52 assert_eq!(size_of::<Foo>(), size_of::<Option<Foo>>());
53 assert_eq!(size_of::<Bar>(), size_of::<Option<Bar>>());
55 assert_eq!(size_of::<(u8, Box<isize>)>(), size_of::<Option<(u8, Box<isize>)>>());
56 // and fixed-size arrays
57 assert_eq!(size_of::<[Box<isize>; 1]>(), size_of::<Option<[Box<isize>; 1]>>());
59 // Should apply to NonZero
60 assert_eq!(size_of::<NonZeroUsize>(), size_of::<Option<NonZeroUsize>>());
61 assert_eq!(size_of::<NonNull<i8>>(), size_of::<Option<NonNull<i8>>>());
63 // Should apply to types that use NonZero internally
64 assert_eq!(size_of::<Vec<isize>>(), size_of::<Option<Vec<isize>>>());
65 assert_eq!(size_of::<Arc<isize>>(), size_of::<Option<Arc<isize>>>());
66 assert_eq!(size_of::<Rc<isize>>(), size_of::<Option<Rc<isize>>>());
68 // Should apply to types that have NonZero transitively
69 assert_eq!(size_of::<String>(), size_of::<Option<String>>());
71 // Should apply to types where the pointer is substituted
72 assert_eq!(size_of::<&u8>(), size_of::<Option<ParamTypeStruct<&u8>>>());
73 assert_eq!(size_of::<&u8>(), size_of::<Option<AssocTypeStruct<&u8>>>());