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// run-pass
#![feature(transparent_unions)]
use std::mem::size_of;
use std::num::NonZeroUsize;
use std::ptr::NonNull;
use std::rc::Rc;
use std::sync::Arc;
trait Trait { fn dummy(&self) { } }
trait Mirror { type Image; }
impl<T> Mirror for T { type Image = T; }
struct ParamTypeStruct<T>(#[allow(unused_tuple_struct_fields)] T);
struct AssocTypeStruct<T>(#[allow(unused_tuple_struct_fields)] <T as Mirror>::Image);
#[repr(transparent)]
union MaybeUninitUnion<T: Copy> {
_value: T,
_uninit: (),
}
fn main() {
// Functions
assert_eq!(size_of::<fn(isize)>(), size_of::<Option<fn(isize)>>());
assert_eq!(size_of::<extern "C" fn(isize)>(), size_of::<Option<extern "C" fn(isize)>>());
// Slices - &str / &[T] / &mut [T]
assert_eq!(size_of::<&str>(), size_of::<Option<&str>>());
assert_eq!(size_of::<&[isize]>(), size_of::<Option<&[isize]>>());
assert_eq!(size_of::<&mut [isize]>(), size_of::<Option<&mut [isize]>>());
// Traits - Box<Trait> / &Trait / &mut Trait
assert_eq!(size_of::<Box<dyn Trait>>(), size_of::<Option<Box<dyn Trait>>>());
assert_eq!(size_of::<&dyn Trait>(), size_of::<Option<&dyn Trait>>());
assert_eq!(size_of::<&mut dyn Trait>(), size_of::<Option<&mut dyn Trait>>());
// Pointers - Box<T>
assert_eq!(size_of::<Box<isize>>(), size_of::<Option<Box<isize>>>());
// The optimization can't apply to raw pointers or unions with a ZST field.
assert!(size_of::<Option<*const isize>>() != size_of::<*const isize>());
assert!(Some(std::ptr::null::<isize>()).is_some()); // Can't collapse None to null
assert_ne!(size_of::<fn(isize)>(), size_of::<Option<MaybeUninitUnion<fn(isize)>>>());
assert_ne!(size_of::<&str>(), size_of::<Option<MaybeUninitUnion<&str>>>());
assert_ne!(size_of::<NonNull<isize>>(), size_of::<Option<MaybeUninitUnion<NonNull<isize>>>>());
struct Foo {
_a: Box<isize>
}
struct Bar(#[allow(unused_tuple_struct_fields)] Box<isize>);
// Should apply through structs
assert_eq!(size_of::<Foo>(), size_of::<Option<Foo>>());
assert_eq!(size_of::<Bar>(), size_of::<Option<Bar>>());
// and tuples
assert_eq!(size_of::<(u8, Box<isize>)>(), size_of::<Option<(u8, Box<isize>)>>());
// and fixed-size arrays
assert_eq!(size_of::<[Box<isize>; 1]>(), size_of::<Option<[Box<isize>; 1]>>());
// Should apply to NonZero
assert_eq!(size_of::<NonZeroUsize>(), size_of::<Option<NonZeroUsize>>());
assert_eq!(size_of::<NonNull<i8>>(), size_of::<Option<NonNull<i8>>>());
// Should apply to types that use NonZero internally
assert_eq!(size_of::<Vec<isize>>(), size_of::<Option<Vec<isize>>>());
assert_eq!(size_of::<Arc<isize>>(), size_of::<Option<Arc<isize>>>());
assert_eq!(size_of::<Rc<isize>>(), size_of::<Option<Rc<isize>>>());
// Should apply to types that have NonZero transitively
assert_eq!(size_of::<String>(), size_of::<Option<String>>());
// Should apply to types where the pointer is substituted
assert_eq!(size_of::<&u8>(), size_of::<Option<ParamTypeStruct<&u8>>>());
assert_eq!(size_of::<&u8>(), size_of::<Option<AssocTypeStruct<&u8>>>());
}
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