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    //! Definitions of integer that is known not to equal zero.

    use crate::fmt;
    use crate::ops::{BitOr, BitOrAssign};
    use crate::str::FromStr;

    use super::from_str_radix;
    use super::{IntErrorKind, ParseIntError};

    macro_rules! doc_comment {
        ($x:expr, $($tt:tt)*) => {
            #[doc = $x]
            $($tt)*
        };
    }

    macro_rules! impl_nonzero_fmt {
        ( #[$stability: meta] ( $( $Trait: ident ),+ ) for $Ty: ident ) => {
            $(
                #[$stability]
                impl fmt::$Trait for $Ty {
                    #[inline]
                    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
                        self.get().fmt(f)
                    }
                }
            )+
        }
    }

    macro_rules! nonzero_integers {
        ( $( #[$stability: meta] $Ty: ident($Int: ty); )+ ) => {
            $(
                doc_comment! {
                    concat!("An integer that is known not to equal zero.

    This enables some memory layout optimization.
    For example, `Option<", stringify!($Ty), ">` is the same size as `", stringify!($Int), "`:

    ```rust
    use std::mem::size_of;
    assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", stringify!($Int),
    ">());
    ```"),
                    #[$stability]
                    #[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
                    #[repr(transparent)]
                    #[rustc_layout_scalar_valid_range_start(1)]
                    #[rustc_nonnull_optimization_guaranteed]
                    pub struct $Ty($Int);
                }

                impl $Ty {
                    /// Creates a non-zero without checking the value.
                    ///
                    /// # Safety
                    ///
                    /// The value must not be zero.
                    #[$stability]
                    #[rustc_const_stable(feature = "nonzero", since = "1.34.0")]
                    #[inline]
                    pub const unsafe fn new_unchecked(n: $Int) -> Self {
                        // SAFETY: this is guaranteed to be safe by the caller.
                        unsafe { Self(n) }
                    }

                    /// Creates a non-zero if the given value is not zero.
                    #[$stability]
                    #[rustc_const_stable(feature = "const_nonzero_int_methods", since = "1.47.0")]
                    #[inline]
                    pub const fn new(n: $Int) -> Option<Self> {
                        if n != 0 {
                            // SAFETY: we just checked that there's no `0`
                            Some(unsafe { Self(n) })
                        } else {
                            None
                        }
                    }

                    /// Returns the value as a primitive type.
                    #[$stability]
                    #[inline]
                    #[rustc_const_stable(feature = "nonzero", since = "1.34.0")]
                    pub const fn get(self) -> $Int {
                        self.0
                    }

                }

                #[stable(feature = "from_nonzero", since = "1.31.0")]
                impl From<$Ty> for $Int {
                    doc_comment! {
                        concat!(
    "Converts a `", stringify!($Ty), "` into an `", stringify!($Int), "`"),
                        fn from(nonzero: $Ty) -> Self {
                            nonzero.0
                        }
                    }
                }

                #[stable(feature = "nonzero_bitor", since = "1.45.0")]
                impl BitOr for $Ty {
                    type Output = Self;
                    #[inline]
                    fn bitor(self, rhs: Self) -> Self::Output {
                        // SAFETY: since `self` and `rhs` are both nonzero, the
                        // result of the bitwise-or will be nonzero.
                        unsafe { $Ty::new_unchecked(self.get() | rhs.get()) }
                    }
                }

                #[stable(feature = "nonzero_bitor", since = "1.45.0")]
                impl BitOr<$Int> for $Ty {
                    type Output = Self;
                    #[inline]
                    fn bitor(self, rhs: $Int) -> Self::Output {
                        // SAFETY: since `self` is nonzero, the result of the
                        // bitwise-or will be nonzero regardless of the value of
                        // `rhs`.
                        unsafe { $Ty::new_unchecked(self.get() | rhs) }
                    }
                }

                #[stable(feature = "nonzero_bitor", since = "1.45.0")]
                impl BitOr<$Ty> for $Int {
                    type Output = $Ty;
                    #[inline]
                    fn bitor(self, rhs: $Ty) -> Self::Output {
                        // SAFETY: since `rhs` is nonzero, the result of the
                        // bitwise-or will be nonzero regardless of the value of
                        // `self`.
                        unsafe { $Ty::new_unchecked(self | rhs.get()) }
                    }
                }

                #[stable(feature = "nonzero_bitor", since = "1.45.0")]
                impl BitOrAssign for $Ty {
                    #[inline]
                    fn bitor_assign(&mut self, rhs: Self) {
                        *self = *self | rhs;
                    }
                }

                #[stable(feature = "nonzero_bitor", since = "1.45.0")]
                impl BitOrAssign<$Int> for $Ty {
                    #[inline]
                    fn bitor_assign(&mut self, rhs: $Int) {
                        *self = *self | rhs;
                    }
                }

                impl_nonzero_fmt! {
                    #[$stability] (Debug, Display, Binary, Octal, LowerHex, UpperHex) for $Ty
                }
            )+
        }
    }

    nonzero_integers! {
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroU8(u8);
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroU16(u16);
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroU32(u32);
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroU64(u64);
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroU128(u128);
        #[stable(feature = "nonzero", since = "1.28.0")] NonZeroUsize(usize);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroI8(i8);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroI16(i16);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroI32(i32);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroI64(i64);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroI128(i128);
        #[stable(feature = "signed_nonzero", since = "1.34.0")] NonZeroIsize(isize);
    }

    macro_rules! from_str_radix_nzint_impl {
        ($($t:ty)*) => {$(
            #[stable(feature = "nonzero_parse", since = "1.35.0")]
            impl FromStr for $t {
                type Err = ParseIntError;
                fn from_str(src: &str) -> Result<Self, Self::Err> {
                    Self::new(from_str_radix(src, 10)?)
                        .ok_or(ParseIntError {
                            kind: IntErrorKind::Zero
                        })
                }
            }
        )*}
    }

    from_str_radix_nzint_impl! { NonZeroU8 NonZeroU16 NonZeroU32 NonZeroU64 NonZeroU128 NonZeroUsize
    NonZeroI8 NonZeroI16 NonZeroI32 NonZeroI64 NonZeroI128 NonZeroIsize }