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