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    use super::{From, TryFrom};
    use crate::num::TryFromIntError;

    mod private {
        /// This trait being unreachable from outside the crate
        /// prevents other implementations of the `FloatToInt` trait,
        /// which allows potentially adding more trait methods after the trait is `#[stable]`.
        #[unstable(feature = "convert_float_to_int", issue = "67057")]
        pub trait Sealed {}
    }

    /// Supporting trait for inherent methods of `f32` and `f64` such as `round_unchecked_to`.
    /// Typically doesn’t need to be used directly.
    #[unstable(feature = "convert_float_to_int", issue = "67057")]
    pub trait FloatToInt<Int>: private::Sealed + Sized {
        #[unstable(feature = "float_approx_unchecked_to", issue = "67058")]
        #[doc(hidden)]
        unsafe fn approx_unchecked(self) -> Int;
    }

    macro_rules! impl_float_to_int {
        ( $Float: ident => $( $Int: ident )+ ) => {
            #[unstable(feature = "convert_float_to_int", issue = "67057")]
            impl private::Sealed for $Float {}
            $(
                #[unstable(feature = "convert_float_to_int", issue = "67057")]
                impl FloatToInt<$Int> for $Float {
                    #[doc(hidden)]
                    #[inline]
                    unsafe fn approx_unchecked(self) -> $Int {
                        crate::intrinsics::float_to_int_approx_unchecked(self)
                    }
                }
            )+
        }
    }

    impl_float_to_int!(f32 => u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);
    impl_float_to_int!(f64 => u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize);

    // Conversion traits for primitive integer and float types
    // Conversions T -> T are covered by a blanket impl and therefore excluded
    // Some conversions from and to usize/isize are not implemented due to portability concerns
    macro_rules! impl_from {
        ($Small: ty, $Large: ty, #[$attr:meta], $doc: expr) => {
            #[$attr]
            #[doc = $doc]
            impl From<$Small> for $Large {
                #[inline]
                fn from(small: $Small) -> Self {
                    small as Self
                }
            }
        };
        ($Small: ty, $Large: ty, #[$attr:meta]) => {
            impl_from!($Small,
                       $Large,
                       #[$attr],
                       concat!("Converts `",
                               stringify!($Small),
                               "` to `",
                               stringify!($Large),
                               "` losslessly."));
        }
    }

    macro_rules! impl_from_bool {
        ($target: ty, #[$attr:meta]) => {
            impl_from!(bool, $target, #[$attr], concat!("Converts a `bool` to a `",
                stringify!($target), "`. The resulting value is `0` for `false` and `1` for `true`
    values.

    # Examples

    ```
    assert_eq!(", stringify!($target), "::from(true), 1);
    assert_eq!(", stringify!($target), "::from(false), 0);
    ```"));
        };
    }

    // Bool -> Any
    impl_from_bool! { u8, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { u16, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { u32, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { u64, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { u128, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { usize, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { i8, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { i16, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { i32, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { i64, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { i128, #[stable(feature = "from_bool", since = "1.28.0")] }
    impl_from_bool! { isize, #[stable(feature = "from_bool", since = "1.28.0")] }

    // Unsigned -> Unsigned
    impl_from! { u8, u16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, u128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u8, usize, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u16, u32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u16, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u16, u128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u32, u64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u32, u128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u64, u128, #[stable(feature = "i128", since = "1.26.0")] }

    // Signed -> Signed
    impl_from! { i8, i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i8, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i8, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i8, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { i8, isize, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i16, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i16, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i16, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { i32, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { i32, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { i64, i128, #[stable(feature = "i128", since = "1.26.0")] }

    // Unsigned -> Signed
    impl_from! { u8, i16, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u8, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u16, i32, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u16, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u16, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u32, i64, #[stable(feature = "lossless_int_conv", since = "1.5.0")] }
    impl_from! { u32, i128, #[stable(feature = "i128", since = "1.26.0")] }
    impl_from! { u64, i128, #[stable(feature = "i128", since = "1.26.0")] }

    // The C99 standard defines bounds on INTPTR_MIN, INTPTR_MAX, and UINTPTR_MAX
    // which imply that pointer-sized integers must be at least 16 bits:
    // https://port70.net/~nsz/c/c99/n1256.html#7.18.2.4
    impl_from! { u16, usize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }
    impl_from! { u8, isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }
    impl_from! { i16, isize, #[stable(feature = "lossless_iusize_conv", since = "1.26.0")] }

    // RISC-V defines the possibility of a 128-bit address space (RV128).

    // CHERI proposes 256-bit “capabilities”. Unclear if this would be relevant to usize/isize.
    // https://www.cl.cam.ac.uk/research/security/ctsrd/pdfs/20171017a-cheri-poster.pdf
    // http://www.csl.sri.com/users/neumann/2012resolve-cheri.pdf

    // Note: integers can only be represented with full precision in a float if
    // they fit in the significand, which is 24 bits in f32 and 53 bits in f64.
    // Lossy float conversions are not implemented at this time.

    // Signed -> Float
    impl_from! { i8, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { i8, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { i16, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { i16, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { i32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }

    // Unsigned -> Float
    impl_from! { u8, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { u8, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { u16, f32, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { u16, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }
    impl_from! { u32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }

    // Float -> Float
    impl_from! { f32, f64, #[stable(feature = "lossless_float_conv", since = "1.6.0")] }

    // no possible bounds violation
    macro_rules! try_from_unbounded {
        ($source:ty, $($target:ty),*) => {$(
            #[stable(feature = "try_from", since = "1.34.0")]
            impl TryFrom<$source> for $target {
                type Error = TryFromIntError;

                /// Try to create the target number type from a source
                /// number type. This returns an error if the source value
                /// is outside of the range of the target type.
                #[inline]
                fn try_from(value: $source) -> Result<Self, Self::Error> {
                    Ok(value as Self)
                }
            }
        )*}
    }

    // only negative bounds
    macro_rules! try_from_lower_bounded {
        ($source:ty, $($target:ty),*) => {$(
            #[stable(feature = "try_from", since = "1.34.0")]
            impl TryFrom<$source> for $target {
                type Error = TryFromIntError;

                /// Try to create the target number type from a source
                /// number type. This returns an error if the source value
                /// is outside of the range of the target type.
                #[inline]
                fn try_from(u: $source) -> Result<Self, Self::Error> {
                    if u >= 0 {
                        Ok(u as Self)
                    } else {
                        Err(TryFromIntError(()))
                    }
                }
            }
        )*}
    }

    // unsigned to signed (only positive bound)
    macro_rules! try_from_upper_bounded {
        ($source:ty, $($target:ty),*) => {$(
            #[stable(feature = "try_from", since = "1.34.0")]
            impl TryFrom<$source> for $target {
                type Error = TryFromIntError;

                /// Try to create the target number type from a source
                /// number type. This returns an error if the source value
                /// is outside of the range of the target type.
                #[inline]
                fn try_from(u: $source) -> Result<Self, Self::Error> {
                    if u > (Self::max_value() as $source) {
                        Err(TryFromIntError(()))
                    } else {
                        Ok(u as Self)
                    }
                }
            }
        )*}
    }

    // all other cases
    macro_rules! try_from_both_bounded {
        ($source:ty, $($target:ty),*) => {$(
            #[stable(feature = "try_from", since = "1.34.0")]
            impl TryFrom<$source> for $target {
                type Error = TryFromIntError;

                /// Try to create the target number type from a source
                /// number type. This returns an error if the source value
                /// is outside of the range of the target type.
                #[inline]
                fn try_from(u: $source) -> Result<Self, Self::Error> {
                    let min = Self::min_value() as $source;
                    let max = Self::max_value() as $source;
                    if u < min || u > max {
                        Err(TryFromIntError(()))
                    } else {
                        Ok(u as Self)
                    }
                }
            }
        )*}
    }

    macro_rules! rev {
        ($mac:ident, $source:ty, $($target:ty),*) => {$(
            $mac!($target, $source);
        )*}
    }

    // intra-sign conversions
    try_from_upper_bounded!(u16, u8);
    try_from_upper_bounded!(u32, u16, u8);
    try_from_upper_bounded!(u64, u32, u16, u8);
    try_from_upper_bounded!(u128, u64, u32, u16, u8);

    try_from_both_bounded!(i16, i8);
    try_from_both_bounded!(i32, i16, i8);
    try_from_both_bounded!(i64, i32, i16, i8);
    try_from_both_bounded!(i128, i64, i32, i16, i8);

    // unsigned-to-signed
    try_from_upper_bounded!(u8, i8);
    try_from_upper_bounded!(u16, i8, i16);
    try_from_upper_bounded!(u32, i8, i16, i32);
    try_from_upper_bounded!(u64, i8, i16, i32, i64);
    try_from_upper_bounded!(u128, i8, i16, i32, i64, i128);

    // signed-to-unsigned
    try_from_lower_bounded!(i8, u8, u16, u32, u64, u128);
    try_from_lower_bounded!(i16, u16, u32, u64, u128);
    try_from_lower_bounded!(i32, u32, u64, u128);
    try_from_lower_bounded!(i64, u64, u128);
    try_from_lower_bounded!(i128, u128);
    try_from_both_bounded!(i16, u8);
    try_from_both_bounded!(i32, u16, u8);
    try_from_both_bounded!(i64, u32, u16, u8);
    try_from_both_bounded!(i128, u64, u32, u16, u8);

    // usize/isize
    try_from_upper_bounded!(usize, isize);
    try_from_lower_bounded!(isize, usize);

    #[cfg(target_pointer_width = "16")]
    mod ptr_try_from_impls {
        use super::TryFromIntError;
        use crate::convert::TryFrom;

        try_from_upper_bounded!(usize, u8);
        try_from_unbounded!(usize, u16, u32, u64, u128);
        try_from_upper_bounded!(usize, i8, i16);
        try_from_unbounded!(usize, i32, i64, i128);

        try_from_both_bounded!(isize, u8);
        try_from_lower_bounded!(isize, u16, u32, u64, u128);
        try_from_both_bounded!(isize, i8);
        try_from_unbounded!(isize, i16, i32, i64, i128);

        rev!(try_from_upper_bounded, usize, u32, u64, u128);
        rev!(try_from_lower_bounded, usize, i8, i16);
        rev!(try_from_both_bounded, usize, i32, i64, i128);

        rev!(try_from_upper_bounded, isize, u16, u32, u64, u128);
        rev!(try_from_both_bounded, isize, i32, i64, i128);
    }

    #[cfg(target_pointer_width = "32")]
    mod ptr_try_from_impls {
        use super::TryFromIntError;
        use crate::convert::TryFrom;

        try_from_upper_bounded!(usize, u8, u16);
        try_from_unbounded!(usize, u32, u64, u128);
        try_from_upper_bounded!(usize, i8, i16, i32);
        try_from_unbounded!(usize, i64, i128);

        try_from_both_bounded!(isize, u8, u16);
        try_from_lower_bounded!(isize, u32, u64, u128);
        try_from_both_bounded!(isize, i8, i16);
        try_from_unbounded!(isize, i32, i64, i128);

        rev!(try_from_unbounded, usize, u32);
        rev!(try_from_upper_bounded, usize, u64, u128);
        rev!(try_from_lower_bounded, usize, i8, i16, i32);
        rev!(try_from_both_bounded, usize, i64, i128);

        rev!(try_from_unbounded, isize, u16);
        rev!(try_from_upper_bounded, isize, u32, u64, u128);
        rev!(try_from_unbounded, isize, i32);
        rev!(try_from_both_bounded, isize, i64, i128);
    }

    #[cfg(target_pointer_width = "64")]
    mod ptr_try_from_impls {
        use super::TryFromIntError;
        use crate::convert::TryFrom;

        try_from_upper_bounded!(usize, u8, u16, u32);
        try_from_unbounded!(usize, u64, u128);
        try_from_upper_bounded!(usize, i8, i16, i32, i64);
        try_from_unbounded!(usize, i128);

        try_from_both_bounded!(isize, u8, u16, u32);
        try_from_lower_bounded!(isize, u64, u128);
        try_from_both_bounded!(isize, i8, i16, i32);
        try_from_unbounded!(isize, i64, i128);

        rev!(try_from_unbounded, usize, u32, u64);
        rev!(try_from_upper_bounded, usize, u128);
        rev!(try_from_lower_bounded, usize, i8, i16, i32, i64);
        rev!(try_from_both_bounded, usize, i128);

        rev!(try_from_unbounded, isize, u16, u32);
        rev!(try_from_upper_bounded, isize, u64, u128);
        rev!(try_from_unbounded, isize, i32, i64);
        rev!(try_from_both_bounded, isize, i128);
    }

    // Conversion traits for non-zero integer types
    use crate::num::NonZeroI128;
    use crate::num::NonZeroI16;
    use crate::num::NonZeroI32;
    use crate::num::NonZeroI64;
    use crate::num::NonZeroI8;
    use crate::num::NonZeroIsize;
    use crate::num::NonZeroU128;
    use crate::num::NonZeroU16;
    use crate::num::NonZeroU32;
    use crate::num::NonZeroU64;
    use crate::num::NonZeroU8;
    use crate::num::NonZeroUsize;

    macro_rules! nzint_impl_from {
        ($Small: ty, $Large: ty, #[$attr:meta], $doc: expr) => {
            #[$attr]
            #[doc = $doc]
            impl From<$Small> for $Large {
                #[inline]
                fn from(small: $Small) -> Self {
                    // SAFETY: input type guarantees the value is non-zero
                    unsafe {
                        Self::new_unchecked(small.get().into())
                    }
                }
            }
        };
        ($Small: ty, $Large: ty, #[$attr:meta]) => {
            nzint_impl_from!($Small,
                       $Large,
                       #[$attr],
                       concat!("Converts `",
                               stringify!($Small),
                               "` to `",
                               stringify!($Large),
                               "` losslessly."));
        }
    }

    // Non-zero Unsigned -> Non-zero Unsigned
    nzint_impl_from! { NonZeroU8, NonZeroU16, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroU32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroU64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroU128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroUsize, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroU32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroU64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroU128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroUsize, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU32, NonZeroU64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU32, NonZeroU128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU64, NonZeroU128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }

    // Non-zero Signed -> Non-zero Signed
    nzint_impl_from! { NonZeroI8, NonZeroI16, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI8, NonZeroI32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI8, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI8, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI8, NonZeroIsize, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI16, NonZeroI32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI16, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI16, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI16, NonZeroIsize, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI32, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI32, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroI64, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }

    // NonZero UnSigned -> Non-zero Signed
    nzint_impl_from! { NonZeroU8, NonZeroI16, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroI32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU8, NonZeroIsize, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroI32, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU16, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU32, NonZeroI64, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU32, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }
    nzint_impl_from! { NonZeroU64, NonZeroI128, #[stable(feature = "nz_int_conv", since = "1.41.0")] }