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// compile-flags: -Z print-type-sizes
// build-pass
// ignore-pass
// ^-- needed because `--pass check` does not emit the output needed.
// FIXME: consider using an attribute instead of side-effects.
// This file illustrates how niche-filling enums are handled,
// modelled after cases like `Option<&u32>`, `Option<bool>` and such.
//
// It uses NonZeroU32 rather than `&_` or `Unique<_>`, because
// the test is not set up to deal with target-dependent pointer width.
//
// It avoids using u64/i64 because on some targets that is only 4-byte
// aligned (while on most it is 8-byte aligned) and so the resulting
// padding and overall computed sizes can be quite different.
#![feature(start)]
#![feature(rustc_attrs)]
#![allow(dead_code)]
use std::num::NonZeroU32;
pub enum MyOption<T> { None, Some(T) }
#[rustc_layout_scalar_valid_range_start(0)]
#[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
pub struct MyNotNegativeOne {
_i: i32,
}
impl<T> Default for MyOption<T> {
fn default() -> Self { MyOption::None }
}
pub enum EmbeddedDiscr {
None,
Record { pre: u8, val: NonZeroU32, post: u16 },
}
impl Default for EmbeddedDiscr {
fn default() -> Self { EmbeddedDiscr::None }
}
#[derive(Default)]
pub struct IndirectNonZero {
pre: u8,
nested: NestedNonZero,
post: u16,
}
pub struct NestedNonZero {
pre: u8,
val: NonZeroU32,
post: u16,
}
impl Default for NestedNonZero {
fn default() -> Self {
NestedNonZero { pre: 0, val: NonZeroU32::new(1).unwrap(), post: 0 }
}
}
pub enum Enum4<A, B, C, D> {
One(A),
Two(B),
Three(C),
Four(D)
}
pub union Union1<A: Copy> {
a: A,
}
pub union Union2<A: Copy, B: Copy> {
a: A,
b: B,
}
#[start]
fn start(_: isize, _: *const *const u8) -> isize {
let _x: MyOption<NonZeroU32> = Default::default();
let _y: EmbeddedDiscr = Default::default();
let _z: MyOption<IndirectNonZero> = Default::default();
let _a: MyOption<bool> = Default::default();
let _b: MyOption<char> = Default::default();
let _c: MyOption<std::cmp::Ordering> = Default::default();
let _d: MyOption<MyOption<u8>> = Default::default();
let _e: Enum4<(), char, (), ()> = Enum4::One(());
let _f: Enum4<(), (), bool, ()> = Enum4::One(());
let _g: Enum4<(), (), (), MyOption<u8>> = Enum4::One(());
let _h: MyOption<MyNotNegativeOne> = Default::default();
// Unions do not currently participate in niche filling.
let _i: MyOption<Union2<NonZeroU32, u32>> = Default::default();
// ...even when theoretically possible.
let _j: MyOption<Union1<NonZeroU32>> = Default::default();
let _k: MyOption<Union2<NonZeroU32, NonZeroU32>> = Default::default();
0
}
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