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//! null pointer optimization preserves type sizes.
//!
//! Verifies that Option<T> has the same size as T for non-null pointer types,
//! and for custom enums that have a niche.
//@ run-pass
// Needs for Nothing variat in Enum
#![allow(dead_code)]
use std::mem;
enum E<T> {
Thing(isize, T),
Nothing((), ((), ()), [i8; 0]),
}
struct S<T>(isize, T);
// These are macros so we get useful assert messages.
macro_rules! check_option {
($T:ty) => {
assert_eq!(mem::size_of::<Option<$T>>(), mem::size_of::<$T>());
};
}
macro_rules! check_fancy {
($T:ty) => {
assert_eq!(mem::size_of::<E<$T>>(), mem::size_of::<S<$T>>());
};
}
macro_rules! check_type {
($T:ty) => {{
check_option!($T);
check_fancy!($T);
}};
}
pub fn main() {
check_type!(&'static isize);
check_type!(Box<isize>);
check_type!(extern "C" fn());
}
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