newtypes 0.4.0

/*
 * SPDX-FileCopyrightText: 2025 CTRLback SCCL.
 * SPDX-License-Identifier: MIT
 */

//!
//! # Newtypes
//!
//! The `newtypes` crate is meant to ease the implementation of the
//! [Newtype](https://rust-unofficial.github.io/patterns/patterns/behavioural/newtype.html)
//! pattern while trying to make as few assumptions as possible.
//!
//! ## Layout guarantee
//!
//! Every type produced by every macro in this crate is annotated with
//! [`#[repr(transparent)]`](https://doc.rust-lang.org/reference/type-layout.html#the-transparent-representation),
//! so its size and alignment match the inner type's. This is a stable part
//! of the crate's contract and will not be removed.
//!
//! ## `newtype!` Macro
//!
//! The `newtype!` macro creates a barebones newtype by wrapping an inner type with
//! a struct, and, if possible, implementing some extra traits for it.
//!
//! By default, all declared structs have visibility `pub`.
//!
//! ```rust
//! use newtypes::*;
//! use serde::{Deserialize, Serialize};
//!
//! newtype!(NewTypeName, u32);
//!
//! // In case we want to automatically derive traits (Note that we can
//! // add as many traits as we need after the `;` character):
//! newtype!(AnotherTypeName, u32; Deserialize, Serialize);
//! ```
//!
//! Example:
//! ```rust
//! use newtypes::*;
//! use serde::{Deserialize, Serialize};
//!
//! newtype!(UserId, u32);
//!
//! newtype!(GroupId, u32; Serialize, Deserialize);
//! ```
//!
//! ### Implemented traits
//!
//! - For all:
//!   - [`Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html)
//!   - [`Into<inner_type>`](https://doc.rust-lang.org/std/convert/trait.Into.html)
//! - For integers:
//!   - [`Clone`](https://doc.rust-lang.org/std/clone/trait.Clone.html)
//!   - [`Copy`](https://doc.rust-lang.org/std/marker/trait.Copy.html)
//!   - [`Hash`](https://doc.rust-lang.org/std/hash/trait.Hash.html)
//!   - [`PartialEq`](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html)
//!   - [`Eq`](https://doc.rust-lang.org/std/cmp/trait.Eq.html)
//! - For floating point numbers:
//!   - [`Clone`](https://doc.rust-lang.org/std/clone/trait.Clone.html)
//!   - [`Copy`](https://doc.rust-lang.org/std/marker/trait.Copy.html)
//!   - [`PartialEq`](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html)
//! - For `String`:
//!   - [`Clone`](https://doc.rust-lang.org/std/clone/trait.Clone.html)
//!   - [`Hash`](https://doc.rust-lang.org/std/hash/trait.Hash.html)
//!   - [`PartialEq`](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html)
//!   - [`Eq`](https://doc.rust-lang.org/std/cmp/trait.Eq.html)
//!
//! > **IMPORTANT:** The inner value is private. If there are no constraints on the
//! > inner value, then we can rely on [`newtype_from!`](#newtype_from-macro) macro
//! > to implement the `From` and `FromStr` traits for us.
//! >
//! > Otherwise we can choose to implement
//! > [`From`](https://doc.rust-lang.org/std/convert/trait.From.html),
//! > [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) and
//! > [`TryFrom`](https://doc.rust-lang.org/std/convert/trait.TryFrom.html)
//! > manually.
//!
//! ## `newtype_ord!` Macro
//!
//! The `newtype_ord!` macro extends the functionality provided with
//! [`newtype!`](#newtype-macro) by implementing the
//! [`PartialOrd`](https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html) and
//! [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) traits
//! (when possible).
//!
//! Example:
//! ```rust
//! use newtypes::*;
//! use serde::{Deserialize, Serialize};
//!
//! newtype_ord!(Rank, u16);
//!
//! newtype_ord!(TicketNumber, u16; Serialize, Deserialize);
//! ```
//!
//! > **NOTE:** It only works for integers, floating point numbers, and `String`.
//!
//! ## `newtype_unit!` Macro
//!
//! The `newtype_unit!` macro extends the functionality provided with
//! [`newtype_ord!`](#newtype_ord-macro) by implementing the
//! [`Add`](https://doc.rust-lang.org/std/ops/trait.Add.html),
//! [`Sub`](https://doc.rust-lang.org/std/ops/trait.Sub.html),
//! [`AddAssign`](https://doc.rust-lang.org/std/ops/trait.AddAssign.html),
//! [`SubAssign`](https://doc.rust-lang.org/std/ops/trait.SubAssign.html), and
//! [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) traits.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//! use serde::Deserialize;
//!
//! newtype_unit!(Weight, f32);
//!
//! newtype_unit!(Length, f32; Deserialize);
//! ```
//!
//! > **NOTE:** It only works for integers and floating point numbers.
//!
//! > **NOTE:** It does not implement arithmetic operations beyond addition and
//! > subtraction. Doing that properly would require a more complex library focused
//! > on dealing with "units" (example: multiplying lengths gives us an area).
//!
//! ## `newtype_struct!` Macro
//!
//! The `newtype_struct!` macro creates a newtype that wraps a user-defined
//! struct (or any non-scalar inner type), implementing
//! [`Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html),
//! [`Clone`](https://doc.rust-lang.org/std/clone/trait.Clone.html),
//! [`PartialEq`](https://doc.rust-lang.org/std/cmp/trait.PartialEq.html), and
//! [`Into<inner_type>`](https://doc.rust-lang.org/std/convert/trait.Into.html).
//!
//! The inner type must itself implement `Debug + Clone + PartialEq`. Extra
//! traits (`Copy`, `Hash`, `Eq`, `Ord`, `PartialOrd`, `Serialize`, …) can be
//! requested by passing them after the `;` separator and will be derived on
//! the generated struct.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! #[derive(Debug, Clone, PartialEq)]
//! pub struct Vec3 { pub x: f32, pub y: f32, pub z: f32 }
//!
//! newtype_struct!(Vertex, Vec3);
//! ```
//!
//! ## `newtype_array!` Macro
//!
//! The `newtype_array!` macro creates a newtype that wraps a fixed-size array
//! `[T; N]` and exposes array-like ergonomics: indexing (single element and
//! ranges), iteration in all three forms (`Self`, `&Self`, `&mut Self`),
//! inherent `len`, `is_empty`, `iter`, `iter_mut`, `as_array`, `as_array_mut`,
//! plus `AsRef<[T]>`, `AsMut<[T]>`, and `Into<[T; N]>`.
//!
//! `Deref<Target = [T]>` is **not** emitted by default. Use
//! [`newtype_array_deref!`](#newtype_array_deref-macro) when full
//! transparent-slice access is desired.
//!
//! Default trait derives depend on the element type: integers get
//! `Copy + Eq + Hash`, floats get `Copy + PartialEq`, `String` gets
//! `Eq + Hash` (no `Copy`), arbitrary types get the conservative
//! `Debug + Clone + PartialEq` baseline. Extra derives can be requested
//! after `;` like every other macro in this crate.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! newtype_array!(MacAddr, u8, 6);
//!
//! let m = MacAddr([0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe]);
//! assert_eq!(0xde, m[0]);
//! assert_eq!(6, m.len());
//! let _slice: &[u8] = &m[1..3];
//! ```
//!
//! With extra derives:
//! ```rust
//! use newtypes::*;
//! use serde::{Deserialize, Serialize};
//!
//! newtype_array!(MacAddr, u8, 6; Serialize, Deserialize);
//! ```
//!
//! `From<[T; N]>` is **not** emitted by default. Combine with
//! [`newtype_from_only!`](#newtype_from_only-macro) if implicit construction
//! from an array is desired.
//!
//! ## `newtype_array_deref!` Macro
//!
//! The `newtype_array_deref!` macro behaves exactly like
//! [`newtype_array!`](#newtype_array-macro) but additionally implements
//! [`Deref<Target = [T]>`](https://doc.rust-lang.org/std/ops/trait.Deref.html)
//! and
//! [`DerefMut`](https://doc.rust-lang.org/std/ops/trait.DerefMut.html).
//!
//! This exposes every slice method (`first`, `last`, `contains`, `fill`,
//! `chunks`, `windows`, `split`, …) directly on the newtype and lets `&Name`
//! coerce to `&[T]` implicitly. The convenience comes at the cost of
//! partially erasing the wrapper at call sites, which can defeat the
//! type-safety motivation of the newtype pattern. Prefer
//! [`newtype_array!`](#newtype_array-macro) unless you specifically want the
//! full slice surface.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! newtype_array_deref!(Buf, u8, 4);
//!
//! let b = Buf([1, 2, 3, 4]);
//! assert_eq!(Some(&1u8), b.first());
//! assert_eq!(Some(&4u8), b.last());
//! assert!(b.contains(&3));
//! ```
//!
//! ## `newtype_validated!` Macro
//!
//! The `newtype_validated!` macro creates a newtype whose constructor enforces
//! an invariant. Validation always runs; there is no `unsafe` escape hatch.
//! Invalid values yield an error.
//!
//! The error type is generated alongside the newtype as a zero-sized struct.
//! Its name must be supplied explicitly because `macro_rules!` cannot
//! synthesise `{Name}Error` on stable Rust without third-party dependencies.
//!
//! `From<inner>` is **not** emitted (it would bypass validation).
//! [`TryFrom<inner>`](https://doc.rust-lang.org/std/convert/trait.TryFrom.html)
//! is emitted and delegates to `Self::new`.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! newtype_validated!(Probability, ProbabilityError, f32, |x: &f32| (0.0..=1.0).contains(x));
//!
//! assert!(Probability::new(0.5).is_ok());
//! assert!(Probability::new(2.0).is_err());
//! ```
//!
//! > **WARNING:** Validation runs only at construction time. Wrapping a type
//! > with interior mutability (e.g. `RefCell`, `Cell`) defeats the invariant
//! > because the inner value can mutate after construction.
//!
//! > **WARNING:** Combining `newtype_validated!` with `newtype_from!` (or
//! > `newtype_from_only!`) on the same newtype emits `From<inner>` and
//! > silently bypasses validation.
//!
//! ## `newtype_from!` Macro
//!
//! The macro `newtype_from!` implements the `From` and `FromStr` traits for us
//! in case it's possible.
//!
//! It has to be used in combination with one of the other ones
//! ([`newtype!`](#newtype-macro), [`newtype_ord!`](#newtype_ord-macro), or
//! [`newtype_unit!`](#newtype_unit-macro)).
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! newtype!(Weight, f32);
//! newtype_from!(Weight, f32);
//! ```
//!
//! > **NOTE:** It only works for integers, floating point numbers, and `String`.
//!
//! ## `newtype_from_only!` Macro
//!
//! The macro `newtype_from_only!` implements only the `From` trait, leaving
//! `FromStr` to the caller. Use it when a type should be constructible from
//! its inner value but should not parse from text.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//!
//! newtype!(VertexIndex, u32);
//! newtype_from_only!(VertexIndex, u32);
//! ```
//!
//! > **NOTE:** It works for integers, floating point numbers, `String`, and
//! > arbitrary inner types.
//!
//! ## `newtype_fromstr!` Macro
//!
//! The macro `newtype_fromstr!` implements only the `FromStr` trait, leaving
//! `From<inner>` to the caller. Use it when a type should parse from text but
//! should not be implicitly constructible from its inner value.
//!
//! Example:
//! ```rust
//! use newtypes::*;
//! use std::str::FromStr;
//!
//! newtype!(Age, u8);
//! newtype_fromstr!(Age, u8);
//!
//! let a = Age::from_str("42").unwrap();
//! ```
//!
//! > **NOTE:** It only works for integers, floating point numbers, and
//! > `String`. For arbitrary inner types implement `FromStr` manually.
//!

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_base {
    ($name:ident, $inner:ty) => {
        #[repr(transparent)]
        #[derive(Debug)]
        pub struct $name($inner);

        impl From<$name> for $inner {
            fn from(value: $name) -> $inner {
                value.0
            }
        }
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        #[repr(transparent)]
        #[derive(Debug, $($derive),+)]
        pub struct $name($inner);

        impl From<$name> for $inner {
            fn from(value: $name) -> $inner {
                value.0
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_clone_traits {
    ($name:ident) => {
        impl Clone for $name {
            fn clone(&self) -> Self {
                Self(self.0.clone())
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_copy_traits {
    ($name:ident) => {
        impl Clone for $name {
            fn clone(&self) -> Self {
                *self
            }
        }

        impl Copy for $name {}
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_partialeq_traits {
    ($name:ident) => {
        impl PartialEq for $name {
            fn eq(&self, other: &Self) -> bool {
                self.0 == other.0
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_eq_traits {
    ($name:ident) => {
        $crate::_nt_partialeq_traits!($name);
        impl Eq for $name {}
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_partialord_traits {
    ($name:ident) => {
        impl PartialOrd for $name {
            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
                self.0.partial_cmp(&other.0)
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_ord_traits {
    ($name:ident) => {
        impl Ord for $name {
            fn cmp(&self, other: &Self) -> std::cmp::Ordering {
                self.0.cmp(&other.0)
            }
        }

        impl PartialOrd for $name {
            fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
                Some(self.cmp(other))
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_hash_traits {
    ($name:ident) => {
        impl std::hash::Hash for $name {
            fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
                self.0.hash(state);
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_addsub_traits {
    ($name:ident) => {
        impl Default for $name {
            fn default() -> Self {
                Self(Default::default())
            }
        }

        impl std::ops::Add<$name> for $name {
            type Output = $name;

            fn add(self, rhs: Self) -> Self::Output {
                $name(self.0 + rhs.0)
            }
        }

        impl std::ops::Add<&$name> for $name {
            type Output = $name;

            fn add(self, rhs: &$name) -> Self::Output {
                $name(self.0 + rhs.0)
            }
        }

        impl std::ops::Add<$name> for &$name {
            type Output = $name;

            fn add(self, rhs: $name) -> Self::Output {
                $name(self.0 + rhs.0)
            }
        }

        impl std::ops::Add<&$name> for &$name {
            type Output = $name;

            fn add(self, rhs: &$name) -> Self::Output {
                $name(self.0 + rhs.0)
            }
        }

        impl std::ops::Sub<$name> for $name {
            type Output = $name;

            fn sub(self, rhs: Self) -> Self::Output {
                $name(self.0 - rhs.0)
            }
        }

        impl std::ops::Sub<&$name> for $name {
            type Output = $name;

            fn sub(self, rhs: &$name) -> Self::Output {
                $name(self.0 - rhs.0)
            }
        }

        impl std::ops::Sub<$name> for &$name {
            type Output = $name;

            fn sub(self, rhs: $name) -> Self::Output {
                $name(self.0 - rhs.0)
            }
        }

        impl std::ops::Sub<&$name> for &$name {
            type Output = $name;

            fn sub(self, rhs: &$name) -> Self::Output {
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            }
        }

        impl std::ops::AddAssign<$name> for $name {
            fn add_assign(&mut self, rhs: $name) {
                self.0 += rhs.0;
            }
        }

        impl std::ops::AddAssign<&$name> for $name {
            fn add_assign(&mut self, rhs: &$name) {
                self.0 += rhs.0;
            }
        }

        impl std::ops::SubAssign<$name> for $name {
            fn sub_assign(&mut self, rhs: $name) {
                self.0 -= rhs.0;
            }
        }

        impl std::ops::SubAssign<&$name> for $name {
            fn sub_assign(&mut self, rhs: &$name) {
                self.0 -= rhs.0;
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_clone {
    ($name:ident, $inner:ty) => {
        $crate::_nt_base!($name, $inner);
        $crate::_nt_clone_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_base!($name, $inner; $($derive),+);
        $crate::_nt_clone_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_copy {
    ($name:ident, $inner:ty) => {
        $crate::_nt_base!($name, $inner);
        $crate::_nt_copy_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_base!($name, $inner; $($derive),+);
        $crate::_nt_copy_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_int {
    ($name:ident, $inner:ty) => {
        $crate::_nt_copy!($name, $inner);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_copy!($name, $inner; $($derive),+);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_float {
    ($name:ident, $inner:ty) => {
        $crate::_nt_copy!($name, $inner);
        $crate::_nt_partialeq_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_copy!($name, $inner; $($derive),+);
        $crate::_nt_partialeq_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_string {
    ($name:ident) => {
        $crate::_nt_clone!($name, String);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
    };

    ($name:ident; $($derive:path),+) => {
        $crate::_nt_clone!($name, String; $($derive),+);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_int_ord {
    ($name:ident, $inner:ty) => {
        $crate::_nt_int!($name, $inner);
        $crate::_nt_ord_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_int!($name, $inner; $($derive),+);
        $crate::_nt_ord_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_float_ord {
    ($name:ident, $inner:ty) => {
        $crate::_nt_float!($name, $inner);
        $crate::_nt_partialord_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_float!($name, $inner; $($derive),+);
        $crate::_nt_partialord_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_string_ord {
    ($name:ident) => {
        $crate::_nt_string!($name);
        $crate::_nt_ord_traits!($name);
    };

    ($name:ident; $($derive:path),+) => {
        $crate::_nt_string!($name; $($derive),+);
        $crate::_nt_ord_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_int_unit {
    ($name:ident, $inner:ty) => {
        $crate::_nt_int_ord!($name, $inner);
        $crate::_nt_addsub_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_int_ord!($name, $inner; $($derive),+);
        $crate::_nt_addsub_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_float_unit {
    ($name:ident, $inner:ty) => {
        $crate::_nt_float_ord!($name, $inner);
        $crate::_nt_addsub_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_float_ord!($name, $inner; $($derive),+);
        $crate::_nt_addsub_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_from_traits {
    ($name:ident, $inner:ty) => {
        impl From<$inner> for $name {
            #[inline(always)]
            fn from(value: $inner) -> Self {
                $name(value)
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_fromstr_traits {
    ($name:ident, $inner:ty, $err:ty) => {
        impl std::str::FromStr for $name {
            type Err = $err;

            fn from_str(s: &str) -> Result<Self, Self::Err> {
                match <$inner>::from_str(s) {
                    Ok(v) => Ok($name(v)),
                    Err(e) => Err(e),
                }
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_int_from {
    ($name:ident, $inner:ty) => {
        $crate::_nt_from_traits!($name, $inner);
        $crate::_nt_fromstr_traits!($name, $inner, std::num::ParseIntError);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_float_from {
    ($name:ident, $inner:ty) => {
        $crate::_nt_from_traits!($name, $inner);
        $crate::_nt_fromstr_traits!($name, $inner, std::num::ParseFloatError);
    };
}

/// The `newtype!` macro creates a barebones newtype by wrapping an inner type with
/// a struct, and, if possible, implementing some extra traits for it.
///
/// By default, all declared structs have visibility `pub`.
///
/// ```rust
/// use newtypes::*;
///
/// newtype!(NewTypeName, u32);
/// ```
///
/// In case we want to automatically derive traits (like serde's
/// `Serialize` or `Deserialize`):
/// ```rust
/// use newtypes::*;
/// use serde::{Deserialize, Serialize};
///
/// newtype!(NewTypeName, u32; Deserialize, Serialize);
/// ```
///
/// Example:
/// ```rust
/// use newtypes::*;
/// use serde::{Deserialize, Serialize};
///
/// newtype!(UserId, u32);
///
/// newtype!(GroupId, u32; Serialize, Deserialize);
/// ```
#[macro_export]
macro_rules! newtype {
    ($name:ident, i8) => { $crate::_nt_int!($name, i8); };
    ($name:ident, u8) => { $crate::_nt_int!($name, u8); };
    ($name:ident, i16) => { $crate::_nt_int!($name, i16); };
    ($name:ident, u16) => { $crate::_nt_int!($name, u16); };
    ($name:ident, i32) => { $crate::_nt_int!($name, i32); };
    ($name:ident, u32) => { $crate::_nt_int!($name, u32); };
    ($name:ident, i64) => { $crate::_nt_int!($name, i64); };
    ($name:ident, u64) => { $crate::_nt_int!($name, u64); };
    ($name:ident, i128) => { $crate::_nt_int!($name, i128); };
    ($name:ident, u128) => { $crate::_nt_int!($name, u128); };
    ($name:ident, isize) => { $crate::_nt_int!($name, isize); };
    ($name:ident, usize) => { $crate::_nt_int!($name, usize); };
    ($name:ident, i8; $($derive:path),+) => { $crate::_nt_int!($name, i8; $($derive),+); };
    ($name:ident, u8; $($derive:path),+) => { $crate::_nt_int!($name, u8; $($derive),+); };
    ($name:ident, i16; $($derive:path),+) => { $crate::_nt_int!($name, i16; $($derive),+); };
    ($name:ident, u16; $($derive:path),+) => { $crate::_nt_int!($name, u16; $($derive),+); };
    ($name:ident, i32; $($derive:path),+) => { $crate::_nt_int!($name, i32; $($derive),+); };
    ($name:ident, u32; $($derive:path),+) => { $crate::_nt_int!($name, u32; $($derive),+); };
    ($name:ident, i64; $($derive:path),+) => { $crate::_nt_int!($name, i64; $($derive),+); };
    ($name:ident, u64; $($derive:path),+) => { $crate::_nt_int!($name, u64; $($derive),+); };
    ($name:ident, i128; $($derive:path),+) => { $crate::_nt_int!($name, i128; $($derive),+); };
    ($name:ident, u128; $($derive:path),+) => { $crate::_nt_int!($name, u128; $($derive),+); };
    ($name:ident, isize; $($derive:path),+) => { $crate::_nt_int!($name, isize; $($derive),+); };
    ($name:ident, usize; $($derive:path),+) => { $crate::_nt_int!($name, usize; $($derive),+); };

    ($name:ident, f32) => { $crate::_nt_float!($name, f32); };
    ($name:ident, f64) => { $crate::_nt_float!($name, f64); };
    ($name:ident, f32; $($derive:path),+) => { $crate::_nt_float!($name, f32; $($derive),+); };
    ($name:ident, f64; $($derive:path),+) => { $crate::_nt_float!($name, f64; $($derive),+); };

    ($name:ident, String) => { $crate::_nt_string!($name); };
    ($name:ident, String; $($derive:path),+) => { $crate::_nt_string!($name; $($derive),+); };

    ($name:ident, $inner:ty) => {
        $crate::_nt_base!($name, $inner);
    };
    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_base!($name, $inner; $($derive),+);
    }
}

/// The `newtype_ord!` macro extends the functionality provided with
/// `newtype!` by implementing the
/// [`PartialOrd`](https://doc.rust-lang.org/std/cmp/trait.PartialOrd.html) and
/// [`Ord`](https://doc.rust-lang.org/std/cmp/trait.Ord.html) traits
/// (when possible).
///
/// Example:
/// ```rust
/// use newtypes::*;
/// use serde::{Deserialize, Serialize};
///
/// newtype_ord!(Rank, u16);
///
/// newtype_ord!(TicketNumber, u16; Serialize, Deserialize);
/// ```
///
/// > **NOTE:** It only works for integers, floating point numbers, and `String`.
#[macro_export]
macro_rules! newtype_ord {
    ($name:ident, i8) => { $crate::_nt_int_ord!($name, i8); };
    ($name:ident, u8) => { $crate::_nt_int_ord!($name, u8); };
    ($name:ident, i16) => { $crate::_nt_int_ord!($name, i16); };
    ($name:ident, u16) => { $crate::_nt_int_ord!($name, u16); };
    ($name:ident, i32) => { $crate::_nt_int_ord!($name, i32); };
    ($name:ident, u32) => { $crate::_nt_int_ord!($name, u32); };
    ($name:ident, i64) => { $crate::_nt_int_ord!($name, i64); };
    ($name:ident, u64) => { $crate::_nt_int_ord!($name, u64); };
    ($name:ident, i128) => { $crate::_nt_int_ord!($name, i128); };
    ($name:ident, u128) => { $crate::_nt_int_ord!($name, u128); };
    ($name:ident, isize) => { $crate::_nt_int_ord!($name, isize); };
    ($name:ident, usize) => { $crate::_nt_int_ord!($name, usize); };
    ($name:ident, i8; $($derive:path),+) => { $crate::_nt_int_ord!($name, i8; $($derive),+); };
    ($name:ident, u8; $($derive:path),+) => { $crate::_nt_int_ord!($name, u8; $($derive),+); };
    ($name:ident, i16; $($derive:path),+) => { $crate::_nt_int_ord!($name, i16; $($derive),+); };
    ($name:ident, u16; $($derive:path),+) => { $crate::_nt_int_ord!($name, u16; $($derive),+); };
    ($name:ident, i32; $($derive:path),+) => { $crate::_nt_int_ord!($name, i32; $($derive),+); };
    ($name:ident, u32; $($derive:path),+) => { $crate::_nt_int_ord!($name, u32; $($derive),+); };
    ($name:ident, i64; $($derive:path),+) => { $crate::_nt_int_ord!($name, i64; $($derive),+); };
    ($name:ident, u64; $($derive:path),+) => { $crate::_nt_int_ord!($name, u64; $($derive),+); };
    ($name:ident, i128; $($derive:path),+) => { $crate::_nt_int_ord!($name, i128; $($derive),+); };
    ($name:ident, u128; $($derive:path),+) => { $crate::_nt_int_ord!($name, u128; $($derive),+); };
    ($name:ident, isize; $($derive:path),+) => { $crate::_nt_int_ord!($name, isize; $($derive),+); };
    ($name:ident, usize; $($derive:path),+) => { $crate::_nt_int_ord!($name, usize; $($derive),+); };

    ($name:ident, f32) => { $crate::_nt_float_ord!($name, f32); };
    ($name:ident, f64) => { $crate::_nt_float_ord!($name, f64); };
    ($name:ident, f32; $($derive:path),+) => { $crate::_nt_float_ord!($name, f32; $($derive),+); };
    ($name:ident, f64; $($derive:path),+) => { $crate::_nt_float_ord!($name, f64; $($derive),+); };

    ($name:ident, String) => { $crate::_nt_string_ord!($name); };
    ($name:ident, String; $($derive:path),+) => { $crate::_nt_string_ord!($name; $($derive),+); };
}

/// The `newtype_unit!` macro extends the functionality provided with
/// `newtype_ord!` by implementing the
/// [`Add`](https://doc.rust-lang.org/std/ops/trait.Add.html),
/// [`Sub`](https://doc.rust-lang.org/std/ops/trait.Sub.html),
/// [`AddAssign`](https://doc.rust-lang.org/std/ops/trait.AddAssign.html),
/// [`SubAssign`](https://doc.rust-lang.org/std/ops/trait.SubAssign.html), and
/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) traits.
///
/// Example:
/// ```rust
/// use newtypes::*;
/// use serde::Deserialize;
///
/// newtype_unit!(Weight, f32);
///
/// newtype_unit!(Length, f32; Deserialize);
/// ```
///
/// > **NOTE:** It only works for integers and floating point numbers.
///
/// > **NOTE:** It does not implement arithmetic operations beyond addition and
/// > subtraction. Doing that properly would require a more complex library focused
/// > on dealing with "units" (example: multiplying lengths gives us an area).
#[macro_export]
macro_rules! newtype_unit {
    ($name:ident, i8) => { $crate::_nt_int_unit!($name, i8); };
    ($name:ident, u8) => { $crate::_nt_int_unit!($name, u8); };
    ($name:ident, i16) => { $crate::_nt_int_unit!($name, i16); };
    ($name:ident, u16) => { $crate::_nt_int_unit!($name, u16); };
    ($name:ident, i32) => { $crate::_nt_int_unit!($name, i32); };
    ($name:ident, u32) => { $crate::_nt_int_unit!($name, u32); };
    ($name:ident, i64) => { $crate::_nt_int_unit!($name, i64); };
    ($name:ident, u64) => { $crate::_nt_int_unit!($name, u64); };
    ($name:ident, i128) => { $crate::_nt_int_unit!($name, i128); };
    ($name:ident, u128) => { $crate::_nt_int_unit!($name, u128); };
    ($name:ident, isize) => { $crate::_nt_int_unit!($name, isize); };
    ($name:ident, usize) => { $crate::_nt_int_unit!($name, usize); };
    ($name:ident, i8; $($derive:path),+) => { $crate::_nt_int_unit!($name, i8; $($derive),+); };
    ($name:ident, u8; $($derive:path),+) => { $crate::_nt_int_unit!($name, u8; $($derive),+); };
    ($name:ident, i16; $($derive:path),+) => { $crate::_nt_int_unit!($name, i16; $($derive),+); };
    ($name:ident, u16; $($derive:path),+) => { $crate::_nt_int_unit!($name, u16; $($derive),+); };
    ($name:ident, i32; $($derive:path),+) => { $crate::_nt_int_unit!($name, i32; $($derive),+); };
    ($name:ident, u32; $($derive:path),+) => { $crate::_nt_int_unit!($name, u32; $($derive),+); };
    ($name:ident, i64; $($derive:path),+) => { $crate::_nt_int_unit!($name, i64; $($derive),+); };
    ($name:ident, u64; $($derive:path),+) => { $crate::_nt_int_unit!($name, u64; $($derive),+); };
    ($name:ident, i128; $($derive:path),+) => { $crate::_nt_int_unit!($name, i128; $($derive),+); };
    ($name:ident, u128; $($derive:path),+) => { $crate::_nt_int_unit!($name, u128; $($derive),+); };
    ($name:ident, isize; $($derive:path),+) => { $crate::_nt_int_unit!($name, isize; $($derive),+); };
    ($name:ident, usize; $($derive:path),+) => { $crate::_nt_int_unit!($name, usize; $($derive),+); };

    ($name:ident, f32) => { $crate::_nt_float_unit!($name, f32); };
    ($name:ident, f64) => { $crate::_nt_float_unit!($name, f64); };
    ($name:ident, f32; $($derive:path),+) => { $crate::_nt_float_unit!($name, f32; $($derive),+); };
    ($name:ident, f64; $($derive:path),+) => { $crate::_nt_float_unit!($name, f64; $($derive),+); };
}

/// The `newtype_struct!` macro creates a newtype that wraps a user-defined
/// struct (or any non-scalar inner type), implementing `Debug`, `Clone`,
/// `PartialEq`, and `Into<inner>`.
///
/// The inner type must itself implement `Debug + Clone + PartialEq`. If
/// extra traits are needed (`Copy`, `Hash`, `Eq`, `Ord`, `PartialOrd`,
/// `Serialize`, …) they can be passed after the `;` separator and will be
/// derived on the generated struct.
///
/// Example:
/// ```rust
/// use newtypes::*;
///
/// #[derive(Debug, Clone, PartialEq)]
/// pub struct Vec3 { pub x: f32, pub y: f32, pub z: f32 }
///
/// newtype_struct!(Vertex, Vec3);
/// ```
///
/// With extra derives:
/// ```rust
/// use newtypes::*;
/// use serde::{Deserialize, Serialize};
///
/// #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
/// pub struct Vec3 { pub x: f32, pub y: f32, pub z: f32 }
///
/// newtype_struct!(Vertex, Vec3; Serialize, Deserialize);
/// ```
#[macro_export]
macro_rules! newtype_struct {
    ($name:ident, $inner:ty) => {
        $crate::_nt_base!($name, $inner);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
    };

    ($name:ident, $inner:ty; $($derive:path),+) => {
        $crate::_nt_base!($name, $inner; $($derive),+);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_validated_impls {
    ($name:ident, $err:ident, $inner:ty, $validator:expr) => {
        #[derive(Debug, Clone, Copy, PartialEq, Eq)]
        pub struct $err;

        impl ::std::fmt::Display for $err {
            fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
                write!(f, concat!("invalid ", stringify!($name), " value"))
            }
        }

        impl ::std::error::Error for $err {}

        impl $name {
            pub fn new(value: $inner) -> ::std::result::Result<Self, $err> {
                if ($validator)(&value) {
                    Ok($name(value))
                } else {
                    Err($err)
                }
            }
        }

        impl ::std::convert::TryFrom<$inner> for $name {
            type Error = $err;

            fn try_from(value: $inner) -> ::std::result::Result<Self, Self::Error> {
                Self::new(value)
            }
        }
    };
}

/// The `newtype_validated!` macro creates a newtype whose constructor enforces
/// an invariant. Validation always runs; there is no `unsafe` escape hatch.
/// Invalid values yield `Err(<ErrorName>)`.
///
/// The error type is generated alongside the newtype as a zero-sized struct
/// implementing `Debug + Clone + Copy + PartialEq + Eq + Display + Error`.
/// Its name must be supplied explicitly because `macro_rules!` cannot
/// synthesise `{Name}Error` without third-party dependencies.
///
/// `From<inner>` is **not** emitted (it would bypass validation). `TryFrom<inner>`
/// is emitted and delegates to `Self::new`.
///
/// The validator must be an expression callable as `Fn(&inner) -> bool`.
/// Closures and free-function paths both work.
///
/// The inner type must implement `Debug + Clone + PartialEq`.
///
/// > **WARNING:** Validation runs only at construction time. Wrapping a type
/// > with interior mutability (e.g. `RefCell`, `Cell`) defeats the invariant
/// > because the inner value can mutate after construction.
///
/// > **WARNING:** Combining `newtype_validated!` with `newtype_from!` (or
/// > `newtype_from_only!`) on the same newtype emits `From<inner>` and
/// > silently bypasses validation. Do not do this.
///
/// Example with a closure:
/// ```rust
/// use newtypes::*;
///
/// newtype_validated!(Probability, ProbabilityError, f32, |x: &f32| (0.0..=1.0).contains(x));
///
/// assert!(Probability::new(0.5).is_ok());
/// assert!(Probability::new(2.0).is_err());
/// ```
///
/// Example with a free function:
/// ```rust
/// use newtypes::*;
///
/// fn is_even(x: &u32) -> bool { x % 2 == 0 }
/// newtype_validated!(EvenU32, EvenU32Error, u32, is_even);
///
/// assert!(EvenU32::new(4).is_ok());
/// assert!(EvenU32::new(5).is_err());
/// ```
#[macro_export]
macro_rules! newtype_validated {
    ($name:ident, $err:ident, $inner:ty, $validator:expr) => {
        $crate::_nt_base!($name, $inner);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_validated_impls!($name, $err, $inner, $validator);
    };

    ($name:ident, $err:ident, $inner:ty, $validator:expr; $($derive:path),+) => {
        $crate::_nt_base!($name, $inner; $($derive),+);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_validated_impls!($name, $err, $inner, $validator);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_base {
    ($name:ident, $t:ty, $n:expr) => {
        #[repr(transparent)]
        #[derive(Debug)]
        pub struct $name([$t; $n]);

        impl From<$name> for [$t; $n] {
            fn from(value: $name) -> [$t; $n] {
                value.0
            }
        }
    };

    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => {
        #[repr(transparent)]
        #[derive(Debug, $($derive),+)]
        pub struct $name([$t; $n]);

        impl From<$name> for [$t; $n] {
            fn from(value: $name) -> [$t; $n] {
                value.0
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_ops {
    ($name:ident, $t:ty, $n:expr) => {
        impl<I: std::slice::SliceIndex<[$t]>> std::ops::Index<I> for $name {
            type Output = I::Output;

            #[inline]
            fn index(&self, index: I) -> &Self::Output {
                std::ops::Index::index(&self.0[..], index)
            }
        }

        impl<I: std::slice::SliceIndex<[$t]>> std::ops::IndexMut<I> for $name {
            #[inline]
            fn index_mut(&mut self, index: I) -> &mut Self::Output {
                std::ops::IndexMut::index_mut(&mut self.0[..], index)
            }
        }

        impl AsRef<[$t]> for $name {
            #[inline]
            fn as_ref(&self) -> &[$t] {
                &self.0[..]
            }
        }

        impl AsMut<[$t]> for $name {
            #[inline]
            fn as_mut(&mut self) -> &mut [$t] {
                &mut self.0[..]
            }
        }

        impl<'a> IntoIterator for &'a $name {
            type Item = &'a $t;
            type IntoIter = std::slice::Iter<'a, $t>;

            #[inline]
            fn into_iter(self) -> Self::IntoIter {
                self.0.iter()
            }
        }

        impl<'a> IntoIterator for &'a mut $name {
            type Item = &'a mut $t;
            type IntoIter = std::slice::IterMut<'a, $t>;

            #[inline]
            fn into_iter(self) -> Self::IntoIter {
                self.0.iter_mut()
            }
        }

        impl IntoIterator for $name {
            type Item = $t;
            type IntoIter = std::array::IntoIter<$t, $n>;

            #[inline]
            fn into_iter(self) -> Self::IntoIter {
                self.0.into_iter()
            }
        }

        impl $name {
            #[inline]
            pub const fn len(&self) -> usize {
                $n
            }

            #[inline]
            pub const fn is_empty(&self) -> bool {
                $n == 0
            }

            #[inline]
            pub fn iter(&self) -> std::slice::Iter<'_, $t> {
                self.0.iter()
            }

            #[inline]
            pub fn iter_mut(&mut self) -> std::slice::IterMut<'_, $t> {
                self.0.iter_mut()
            }

            #[inline]
            pub const fn as_array(&self) -> &[$t; $n] {
                &self.0
            }

            #[inline]
            pub const fn as_array_mut(&mut self) -> &mut [$t; $n] {
                &mut self.0
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_deref_impls {
    ($name:ident, $t:ty) => {
        impl std::ops::Deref for $name {
            type Target = [$t];

            #[inline]
            fn deref(&self) -> &[$t] {
                &self.0[..]
            }
        }

        impl std::ops::DerefMut for $name {
            #[inline]
            fn deref_mut(&mut self) -> &mut [$t] {
                &mut self.0[..]
            }
        }
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_int {
    ($name:ident, $t:ty, $n:expr) => {
        $crate::_nt_array_base!($name, $t, $n);
        $crate::_nt_copy_traits!($name);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };

    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => {
        $crate::_nt_array_base!($name, $t, $n; $($derive),+);
        $crate::_nt_copy_traits!($name);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_float {
    ($name:ident, $t:ty, $n:expr) => {
        $crate::_nt_array_base!($name, $t, $n);
        $crate::_nt_copy_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };

    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => {
        $crate::_nt_array_base!($name, $t, $n; $($derive),+);
        $crate::_nt_copy_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_string {
    ($name:ident, $n:expr) => {
        $crate::_nt_array_base!($name, String, $n);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
        $crate::_nt_array_ops!($name, String, $n);
    };

    ($name:ident, $n:expr; $($derive:path),+) => {
        $crate::_nt_array_base!($name, String, $n; $($derive),+);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_eq_traits!($name);
        $crate::_nt_hash_traits!($name);
        $crate::_nt_array_ops!($name, String, $n);
    };
}

#[doc(hidden)]
#[macro_export]
macro_rules! _nt_array_generic {
    ($name:ident, $t:ty, $n:expr) => {
        $crate::_nt_array_base!($name, $t, $n);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };

    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => {
        $crate::_nt_array_base!($name, $t, $n; $($derive),+);
        $crate::_nt_clone_traits!($name);
        $crate::_nt_partialeq_traits!($name);
        $crate::_nt_array_ops!($name, $t, $n);
    };
}

/// The `newtype_array!` macro creates a newtype that wraps a fixed-size array
/// `[T; N]` and exposes array-like ergonomics: indexing (single element and
/// ranges), iteration in all three forms (`Self`, `&Self`, `&mut Self`),
/// inherent `len`, `is_empty`, `iter`, `iter_mut`, `as_array`, `as_array_mut`,
/// plus `AsRef<[T]>`, `AsMut<[T]>`, and `Into<[T; N]>`.
///
/// `Deref<Target = [T]>` is **not** emitted (it would erase the wrapper at
/// every method call and defeat the type-safety reason to introduce a
/// newtype). For users who explicitly want full transparent-slice access, use
/// [`newtype_array_deref!`](#newtype_array_deref-macro) instead.
///
/// `From<[T; N]>` is **not** emitted by default. Pair the macro with
/// [`newtype_from_only!`](#newtype_from_only-macro) if implicit construction
/// from an array is desired.
///
/// Default derives depend on the element type:
/// - integers (`i8`..`i128`, `u8`..`u128`, `isize`, `usize`):
///   `Debug, Clone, Copy, PartialEq, Eq, Hash`
/// - floats (`f32`, `f64`): `Debug, Clone, Copy, PartialEq`
/// - `String`: `Debug, Clone, PartialEq, Eq, Hash`
/// - any other element type: `Debug, Clone, PartialEq` (the inner type must
///   itself implement these)
///
/// Extra derives can be requested after `;`.
///
/// Example:
/// ```rust
/// use newtypes::*;
///
/// newtype_array!(MacAddr, u8, 6);
///
/// let m = MacAddr([0xde, 0xad, 0xbe, 0xef, 0xca, 0xfe]);
/// assert_eq!(0xde, m[0]);
/// assert_eq!(6, m.len());
/// for byte in &m { let _ = byte; }
/// ```
///
/// With extra derives:
/// ```rust
/// use newtypes::*;
/// use serde::{Deserialize, Serialize};
///
/// newtype_array!(MacAddr, u8, 6; Serialize, Deserialize);
/// ```
#[macro_export]
macro_rules! newtype_array {
    ($name:ident, i8, $n:expr) => { $crate::_nt_array_int!($name, i8, $n); };
    ($name:ident, u8, $n:expr) => { $crate::_nt_array_int!($name, u8, $n); };
    ($name:ident, i16, $n:expr) => { $crate::_nt_array_int!($name, i16, $n); };
    ($name:ident, u16, $n:expr) => { $crate::_nt_array_int!($name, u16, $n); };
    ($name:ident, i32, $n:expr) => { $crate::_nt_array_int!($name, i32, $n); };
    ($name:ident, u32, $n:expr) => { $crate::_nt_array_int!($name, u32, $n); };
    ($name:ident, i64, $n:expr) => { $crate::_nt_array_int!($name, i64, $n); };
    ($name:ident, u64, $n:expr) => { $crate::_nt_array_int!($name, u64, $n); };
    ($name:ident, i128, $n:expr) => { $crate::_nt_array_int!($name, i128, $n); };
    ($name:ident, u128, $n:expr) => { $crate::_nt_array_int!($name, u128, $n); };
    ($name:ident, isize, $n:expr) => { $crate::_nt_array_int!($name, isize, $n); };
    ($name:ident, usize, $n:expr) => { $crate::_nt_array_int!($name, usize, $n); };
    ($name:ident, i8, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i8, $n; $($derive),+); };
    ($name:ident, u8, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u8, $n; $($derive),+); };
    ($name:ident, i16, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i16, $n; $($derive),+); };
    ($name:ident, u16, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u16, $n; $($derive),+); };
    ($name:ident, i32, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i32, $n; $($derive),+); };
    ($name:ident, u32, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u32, $n; $($derive),+); };
    ($name:ident, i64, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i64, $n; $($derive),+); };
    ($name:ident, u64, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u64, $n; $($derive),+); };
    ($name:ident, i128, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i128, $n; $($derive),+); };
    ($name:ident, u128, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u128, $n; $($derive),+); };
    ($name:ident, isize, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, isize, $n; $($derive),+); };
    ($name:ident, usize, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, usize, $n; $($derive),+); };

    ($name:ident, f32, $n:expr) => { $crate::_nt_array_float!($name, f32, $n); };
    ($name:ident, f64, $n:expr) => { $crate::_nt_array_float!($name, f64, $n); };
    ($name:ident, f32, $n:expr; $($derive:path),+) => { $crate::_nt_array_float!($name, f32, $n; $($derive),+); };
    ($name:ident, f64, $n:expr; $($derive:path),+) => { $crate::_nt_array_float!($name, f64, $n; $($derive),+); };

    ($name:ident, String, $n:expr) => { $crate::_nt_array_string!($name, $n); };
    ($name:ident, String, $n:expr; $($derive:path),+) => { $crate::_nt_array_string!($name, $n; $($derive),+); };

    ($name:ident, $t:ty, $n:expr) => { $crate::_nt_array_generic!($name, $t, $n); };
    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => { $crate::_nt_array_generic!($name, $t, $n; $($derive),+); };
}

/// The `newtype_array_deref!` macro behaves exactly like
/// [`newtype_array!`](#newtype_array-macro) but additionally implements
/// [`Deref<Target = [T]>`](https://doc.rust-lang.org/std/ops/trait.Deref.html)
/// and
/// [`DerefMut`](https://doc.rust-lang.org/std/ops/trait.DerefMut.html).
///
/// This exposes every slice method (`first`, `last`, `contains`, `fill`, `chunks`,
/// `windows`, `split`, …) on the newtype directly, as well as triggering
/// implicit `&Name -> &[T]` coercion. That convenience comes at the cost of
/// partially erasing the wrapper at the call site, which can defeat the
/// type-safety motivation of the newtype pattern. Prefer
/// [`newtype_array!`](#newtype_array-macro) and access the slice through
/// `.as_ref()` / `.iter()` / indexing unless you specifically want the full
/// slice surface.
///
/// Example:
/// ```rust
/// use newtypes::*;
///
/// newtype_array_deref!(Buf, u8, 4);
///
/// let b = Buf([1, 2, 3, 4]);
/// assert_eq!(Some(&1u8), b.first());
/// assert_eq!(Some(&4u8), b.last());
/// assert!(b.contains(&3));
/// ```
#[macro_export]
macro_rules! newtype_array_deref {
    ($name:ident, i8, $n:expr) => { $crate::_nt_array_int!($name, i8, $n); $crate::_nt_array_deref_impls!($name, i8); };
    ($name:ident, u8, $n:expr) => { $crate::_nt_array_int!($name, u8, $n); $crate::_nt_array_deref_impls!($name, u8); };
    ($name:ident, i16, $n:expr) => { $crate::_nt_array_int!($name, i16, $n); $crate::_nt_array_deref_impls!($name, i16); };
    ($name:ident, u16, $n:expr) => { $crate::_nt_array_int!($name, u16, $n); $crate::_nt_array_deref_impls!($name, u16); };
    ($name:ident, i32, $n:expr) => { $crate::_nt_array_int!($name, i32, $n); $crate::_nt_array_deref_impls!($name, i32); };
    ($name:ident, u32, $n:expr) => { $crate::_nt_array_int!($name, u32, $n); $crate::_nt_array_deref_impls!($name, u32); };
    ($name:ident, i64, $n:expr) => { $crate::_nt_array_int!($name, i64, $n); $crate::_nt_array_deref_impls!($name, i64); };
    ($name:ident, u64, $n:expr) => { $crate::_nt_array_int!($name, u64, $n); $crate::_nt_array_deref_impls!($name, u64); };
    ($name:ident, i128, $n:expr) => { $crate::_nt_array_int!($name, i128, $n); $crate::_nt_array_deref_impls!($name, i128); };
    ($name:ident, u128, $n:expr) => { $crate::_nt_array_int!($name, u128, $n); $crate::_nt_array_deref_impls!($name, u128); };
    ($name:ident, isize, $n:expr) => { $crate::_nt_array_int!($name, isize, $n); $crate::_nt_array_deref_impls!($name, isize); };
    ($name:ident, usize, $n:expr) => { $crate::_nt_array_int!($name, usize, $n); $crate::_nt_array_deref_impls!($name, usize); };
    ($name:ident, i8, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i8, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, i8); };
    ($name:ident, u8, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u8, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, u8); };
    ($name:ident, i16, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i16, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, i16); };
    ($name:ident, u16, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u16, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, u16); };
    ($name:ident, i32, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i32, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, i32); };
    ($name:ident, u32, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u32, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, u32); };
    ($name:ident, i64, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i64, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, i64); };
    ($name:ident, u64, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u64, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, u64); };
    ($name:ident, i128, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, i128, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, i128); };
    ($name:ident, u128, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, u128, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, u128); };
    ($name:ident, isize, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, isize, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, isize); };
    ($name:ident, usize, $n:expr; $($derive:path),+) => { $crate::_nt_array_int!($name, usize, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, usize); };

    ($name:ident, f32, $n:expr) => { $crate::_nt_array_float!($name, f32, $n); $crate::_nt_array_deref_impls!($name, f32); };
    ($name:ident, f64, $n:expr) => { $crate::_nt_array_float!($name, f64, $n); $crate::_nt_array_deref_impls!($name, f64); };
    ($name:ident, f32, $n:expr; $($derive:path),+) => { $crate::_nt_array_float!($name, f32, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, f32); };
    ($name:ident, f64, $n:expr; $($derive:path),+) => { $crate::_nt_array_float!($name, f64, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, f64); };

    ($name:ident, String, $n:expr) => { $crate::_nt_array_string!($name, $n); $crate::_nt_array_deref_impls!($name, String); };
    ($name:ident, String, $n:expr; $($derive:path),+) => { $crate::_nt_array_string!($name, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, String); };

    ($name:ident, $t:ty, $n:expr) => { $crate::_nt_array_generic!($name, $t, $n); $crate::_nt_array_deref_impls!($name, $t); };
    ($name:ident, $t:ty, $n:expr; $($derive:path),+) => { $crate::_nt_array_generic!($name, $t, $n; $($derive),+); $crate::_nt_array_deref_impls!($name, $t); };
}

/// The macro `newtype_from!` implements the `From` and `FromStr` traits for us
/// in case it's possible.
///
/// It has to be used in combination with one of the other ones
/// (`newtype!`, `newtype_ord!`, or `newtype_unit!`).
///
/// Example:
/// ```rust
/// use newtypes::*;
///
/// newtype!(Weight, f32);
/// newtype_from!(Weight, f32);
/// ```
///
/// > **NOTE:** It only works for integers, floating point numbers, and `String`.
#[macro_export]
macro_rules! newtype_from {
    ($name:ident, i8) => {
        $crate::_nt_int_from!($name, i8);
    };
    ($name:ident, u8) => {
        $crate::_nt_int_from!($name, u8);
    };
    ($name:ident, i16) => {
        $crate::_nt_int_from!($name, i16);
    };
    ($name:ident, u16) => {
        $crate::_nt_int_from!($name, u16);
    };
    ($name:ident, i32) => {
        $crate::_nt_int_from!($name, i32);
    };
    ($name:ident, u32) => {
        $crate::_nt_int_from!($name, u32);
    };
    ($name:ident, i64) => {
        $crate::_nt_int_from!($name, i64);
    };
    ($name:ident, u64) => {
        $crate::_nt_int_from!($name, u64);
    };
    ($name:ident, i128) => {
        $crate::_nt_int_from!($name, i128);
    };
    ($name:ident, u128) => {
        $crate::_nt_int_from!($name, u128);
    };
    ($name:ident, isize) => {
        $crate::_nt_int_from!($name, isize);
    };
    ($name:ident, usize) => {
        $crate::_nt_int_from!($name, usize);
    };

    ($name:ident, f32) => {
        $crate::_nt_float_from!($name, f32);
    };
    ($name:ident, f64) => {
        $crate::_nt_float_from!($name, f64);
    };

    ($name:ident, String) => {
        impl From<String> for $name {
            #[inline(always)]
            fn from(value: String) -> Self {
                $name(value)
            }
        }

        impl From<&str> for $name {
            #[inline(always)]
            fn from(value: &str) -> Self {
                $name(value.into())
            }
        }

        impl std::str::FromStr for $name {
            type Err = std::convert::Infallible;

            #[inline(always)]
            fn from_str(s: &str) -> Result<Self, Self::Err> {
                Ok($name(String::from_str(s).unwrap()))
            }
        }
    };

    ($name:ident, $inner:ty) => {
        impl From<$inner> for $name {
            #[inline(always)]
            fn from(value: $inner) -> Self {
                $name(value)
            }
        }
    };
}

/// The macro `newtype_from_only!` implements only the `From` trait for a
/// newtype, leaving `FromStr` to the caller. Use it when a type should be
/// constructible from its inner value but should not parse from text.
///
/// It has to be used in combination with one of the other ones
/// (`newtype!`, `newtype_ord!`, `newtype_struct!`, or `newtype_unit!`).
///
/// Example:
/// ```rust
/// use newtypes::*;
///
/// newtype!(VertexIndex, u32);
/// newtype_from_only!(VertexIndex, u32);
/// ```
///
/// > **NOTE:** It works for integers, floating point numbers, `String`, and
/// > arbitrary inner types.
#[macro_export]
macro_rules! newtype_from_only {
    ($name:ident, i8) => {
        $crate::_nt_from_traits!($name, i8);
    };
    ($name:ident, u8) => {
        $crate::_nt_from_traits!($name, u8);
    };
    ($name:ident, i16) => {
        $crate::_nt_from_traits!($name, i16);
    };
    ($name:ident, u16) => {
        $crate::_nt_from_traits!($name, u16);
    };
    ($name:ident, i32) => {
        $crate::_nt_from_traits!($name, i32);
    };
    ($name:ident, u32) => {
        $crate::_nt_from_traits!($name, u32);
    };
    ($name:ident, i64) => {
        $crate::_nt_from_traits!($name, i64);
    };
    ($name:ident, u64) => {
        $crate::_nt_from_traits!($name, u64);
    };
    ($name:ident, i128) => {
        $crate::_nt_from_traits!($name, i128);
    };
    ($name:ident, u128) => {
        $crate::_nt_from_traits!($name, u128);
    };
    ($name:ident, isize) => {
        $crate::_nt_from_traits!($name, isize);
    };
    ($name:ident, usize) => {
        $crate::_nt_from_traits!($name, usize);
    };

    ($name:ident, f32) => {
        $crate::_nt_from_traits!($name, f32);
    };
    ($name:ident, f64) => {
        $crate::_nt_from_traits!($name, f64);
    };

    ($name:ident, String) => {
        impl From<String> for $name {
            #[inline(always)]
            fn from(value: String) -> Self {
                $name(value)
            }
        }

        impl From<&str> for $name {
            #[inline(always)]
            fn from(value: &str) -> Self {
                $name(value.into())
            }
        }
    };

    ($name:ident, $inner:ty) => {
        $crate::_nt_from_traits!($name, $inner);
    };
}

/// The macro `newtype_fromstr!` implements only the `FromStr` trait for a
/// newtype, leaving `From<inner>` to the caller. Use it when a type should
/// parse from text but should not be implicitly constructible from its inner
/// value.
///
/// It has to be used in combination with one of the other ones
/// (`newtype!`, `newtype_ord!`, or `newtype_unit!`).
///
/// Example:
/// ```rust
/// use newtypes::*;
/// use std::str::FromStr;
///
/// newtype!(Age, u8);
/// newtype_fromstr!(Age, u8);
///
/// let a = Age::from_str("42").unwrap();
/// ```
///
/// > **NOTE:** It only works for integers, floating point numbers, and
/// > `String`. For arbitrary inner types implement `FromStr` manually.
#[macro_export]
macro_rules! newtype_fromstr {
    ($name:ident, i8) => {
        $crate::_nt_fromstr_traits!($name, i8, std::num::ParseIntError);
    };
    ($name:ident, u8) => {
        $crate::_nt_fromstr_traits!($name, u8, std::num::ParseIntError);
    };
    ($name:ident, i16) => {
        $crate::_nt_fromstr_traits!($name, i16, std::num::ParseIntError);
    };
    ($name:ident, u16) => {
        $crate::_nt_fromstr_traits!($name, u16, std::num::ParseIntError);
    };
    ($name:ident, i32) => {
        $crate::_nt_fromstr_traits!($name, i32, std::num::ParseIntError);
    };
    ($name:ident, u32) => {
        $crate::_nt_fromstr_traits!($name, u32, std::num::ParseIntError);
    };
    ($name:ident, i64) => {
        $crate::_nt_fromstr_traits!($name, i64, std::num::ParseIntError);
    };
    ($name:ident, u64) => {
        $crate::_nt_fromstr_traits!($name, u64, std::num::ParseIntError);
    };
    ($name:ident, i128) => {
        $crate::_nt_fromstr_traits!($name, i128, std::num::ParseIntError);
    };
    ($name:ident, u128) => {
        $crate::_nt_fromstr_traits!($name, u128, std::num::ParseIntError);
    };
    ($name:ident, isize) => {
        $crate::_nt_fromstr_traits!($name, isize, std::num::ParseIntError);
    };
    ($name:ident, usize) => {
        $crate::_nt_fromstr_traits!($name, usize, std::num::ParseIntError);
    };

    ($name:ident, f32) => {
        $crate::_nt_fromstr_traits!($name, f32, std::num::ParseFloatError);
    };
    ($name:ident, f64) => {
        $crate::_nt_fromstr_traits!($name, f64, std::num::ParseFloatError);
    };

    ($name:ident, String) => {
        impl std::str::FromStr for $name {
            type Err = std::convert::Infallible;

            #[inline(always)]
            fn from_str(s: &str) -> Result<Self, Self::Err> {
                Ok($name(String::from_str(s).unwrap()))
            }
        }
    };
}

#[cfg(test)]
mod tests_newtype {
    newtype!(UserId, u32);
    newtype_from!(UserId, u32);

    newtype!(Weight, f32);
    newtype_from!(Weight, f32);

    newtype!(StrId, String);
    newtype_from!(StrId, String);

    #[test]
    fn test_integers_cmp() {
        let v1 = UserId::from(42);
        let v2 = UserId::from(1001);
        let v3 = UserId::from(42);

        assert!(v1 != v2);
        assert!(v2 != v3);
        assert!(v1 == v1);
        assert!(v1 == v3);
    }

    #[test]
    #[allow(clippy::clone_on_copy)]
    fn test_integers_copy() {
        let v1 = UserId::from(42);
        let v2 = UserId::from(1001);

        #[allow(unused)]
        let mut v3 = UserId::from(0);

        v3 = v1;
        assert_eq!(UserId(42), v3);
        v3 = v2;
        assert_eq!(UserId(1001), v3);

        v3 = v1.clone();
        assert_eq!(UserId(42), v3);
        v3 = v2.clone();
        assert_eq!(UserId(1001), v3);
    }

    #[test]
    fn test_integers_into() {
        let v1 = UserId::from(42);
        assert_eq!(42_u32, v1.into());
    }

    #[test]
    fn test_float_cmp() {
        let v1 = Weight::from(42.0);
        let v2 = Weight::from(1001.0);
        let v3 = Weight::from(42.0);

        assert!(v1 != v2);
        assert!(v2 != v3);
        assert!(v1 == v1);
        assert!(v1 == v3);
    }

    #[test]
    #[allow(clippy::clone_on_copy)]
    fn test_float_copy() {
        let v1 = Weight::from(42.0);
        let v2 = Weight::from(1001.0);

        #[allow(unused)]
        let mut v3 = Weight::from(0.0);

        v3 = v1;
        assert_eq!(Weight(42.0), v3);
        v3 = v2;
        assert_eq!(Weight(1001.0), v3);

        v3 = v1.clone();
        assert_eq!(Weight(42.0), v3);
        v3 = v2.clone();
        assert_eq!(Weight(1001.0), v3);
    }

    #[test]
    fn test_float_into() {
        let v1 = Weight::from(42.0);
        assert_eq!(42_f32, v1.into());
    }

    #[test]
    fn test_string_cmp() {
        let v1 = StrId::from("42");
        let v2 = StrId::from("1001");
        let v3 = StrId::from("42");

        assert!(v1 != v2);
        assert!(v2 != v3);
        assert!(v1 == v1);
        assert!(v1 == v3);
    }

    #[test]
    fn test_string_copy() {
        let v1 = StrId::from("42");
        let v2 = StrId::from("1001");

        #[allow(unused)]
        let mut v3 = StrId::from("0");

        v3 = v1.clone();
        assert_eq!(StrId("42".into()), v3);
        v3 = v2.clone();
        assert_eq!(StrId("1001".into()), v3);
    }

    #[test]
    fn test_string_into() {
        let v1 = StrId::from("42");

        let s: String = v1.into();
        assert_eq!("42", s);
    }
}

#[cfg(test)]
mod tests_newtype_ord {
    newtype_ord!(Weight, u32);
    newtype_from!(Weight, u32);

    newtype_ord!(Height, f32);
    newtype_from!(Height, f32);

    newtype_ord!(Name, String);
    newtype_from!(Name, String);

    #[test]
    fn test_integers_cmp() {
        let w1 = Weight::from(100);
        let w2 = Weight::from(150);

        assert!(w1 <= w2);
        assert!(w1 < w2);
        assert!(w2 >= w1);
        assert!(w2 > w1);
    }

    #[test]
    fn test_float_cmp() {
        let h1 = Height::from(100.0);
        let h2 = Height::from(150.0);

        assert!(h1 <= h2);
        assert!(h1 < h2);
        assert!(h2 >= h1);
        assert!(h2 > h1);
    }

    #[test]
    fn test_string_cmp() {
        let n1 = Name::from("Alan");
        let n2 = Name::from("Julia");

        assert!(n1 <= n2);
        assert!(n1 < n2);
        assert!(n2 >= n1);
        assert!(n2 > n1);
    }
}

#[cfg(test)]
mod tests_newtype_unit {
    newtype_unit!(Units, i32);
    newtype_from!(Units, i32);

    #[test]
    fn test_integers_add() {
        let u1 = Units::from(100);
        let u2 = Units::from(50);
        let mut u3 = Units::from(200);

        assert_eq!(Units(150), u1 + u2);
        assert_eq!(Units(150), u2 + u1);

        u3 += u2;
        assert_eq!(Units(250), u3);
    }

    #[test]
    fn test_integers_sub() {
        let u1 = Units::from(100);
        let u2 = Units::from(50);
        let mut u3 = Units::from(200);

        assert_eq!(Units(50), u1 - u2);
        assert_eq!(Units(-50), u2 - u1);

        u3 -= u2;
        assert_eq!(Units(150), u3);
    }
}

#[cfg(test)]
mod tests_newtype_from {
    use std::str::FromStr;

    newtype!(UserId, u32);
    newtype_from!(UserId, u32);

    newtype!(Weight, f32);
    newtype_from!(Weight, f32);

    newtype!(Name, String);
    newtype_from!(Name, String);

    #[test]
    fn test_integer_fromstr() {
        assert_eq!(Ok(UserId(42)), UserId::from_str("42"));
        assert!(UserId::from_str("hello").is_err());
    }

    #[test]
    fn test_float_fromstr() {
        assert_eq!(Ok(Weight(42.0)), Weight::from_str("42.0"));
        assert!(Weight::from_str("hello").is_err());
    }

    #[test]
    fn test_string_fromstr() {
        assert_eq!(Ok(Name("John".into())), Name::from_str("John"));
    }
}

#[cfg(test)]
mod tests_newtype_from_split {
    use std::str::FromStr;

    newtype!(IntFromOnly, u32);
    newtype_from_only!(IntFromOnly, u32);

    newtype!(FloatFromOnly, f32);
    newtype_from_only!(FloatFromOnly, f32);

    newtype!(StrFromOnly, String);
    newtype_from_only!(StrFromOnly, String);

    #[derive(Debug)]
    pub struct Inner(u32);
    newtype!(StructFromOnly, Inner);
    newtype_from_only!(StructFromOnly, Inner);

    newtype!(IntFromStr, u32);
    newtype_fromstr!(IntFromStr, u32);

    newtype!(FloatFromStr, f32);
    newtype_fromstr!(FloatFromStr, f32);

    newtype!(StrFromStr, String);
    newtype_fromstr!(StrFromStr, String);

    newtype!(BothInt, u32);
    newtype_from_only!(BothInt, u32);
    newtype_fromstr!(BothInt, u32);

    #[test]
    fn test_from_only_integer() {
        let v: IntFromOnly = 42_u32.into();
        let n: u32 = v.into();
        assert_eq!(42, n);
    }

    #[test]
    fn test_from_only_float() {
        let v: FloatFromOnly = 1.5_f32.into();
        let n: f32 = v.into();
        assert!((n - 1.5).abs() < f32::EPSILON);
    }

    #[test]
    fn test_from_only_string_owned() {
        let v: StrFromOnly = String::from("hello").into();
        let s: String = v.into();
        assert_eq!("hello", s);
    }

    #[test]
    fn test_from_only_string_slice() {
        let v: StrFromOnly = "world".into();
        let s: String = v.into();
        assert_eq!("world", s);
    }

    #[test]
    fn test_from_only_struct() {
        let v: StructFromOnly = Inner(7).into();
        let inner: Inner = v.into();
        assert_eq!(7, inner.0);
    }

    #[test]
    fn test_fromstr_integer() {
        let v = IntFromStr::from_str("99").unwrap();
        assert_eq!(99_u32, v.into());
        assert!(IntFromStr::from_str("nope").is_err());
    }

    #[test]
    fn test_fromstr_float() {
        let v = FloatFromStr::from_str("3.25").unwrap();
        let n: f32 = v.into();
        assert!((n - 3.25).abs() < f32::EPSILON);
        assert!(FloatFromStr::from_str("nope").is_err());
    }

    #[test]
    fn test_fromstr_string() {
        let v = StrFromStr::from_str("greetings").unwrap();
        let s: String = v.into();
        assert_eq!("greetings", s);
    }

    #[test]
    fn test_combined_equivalent_to_newtype_from() {
        let from_int: BothInt = 7_u32.into();
        let parsed = BothInt::from_str("7").unwrap();
        assert_eq!(7_u32, from_int.into());
        assert_eq!(7_u32, parsed.into());
    }
}

#[cfg(test)]
mod tests_newtype_struct {
    #[derive(Debug, Clone, PartialEq)]
    pub struct Point2D {
        pub x: f32,
        pub y: f32,
    }

    newtype_struct!(Vertex, Point2D);

    newtype_struct!(Numbers, Vec<u32>);

    #[derive(Debug, Clone, PartialEq)]
    struct Container {
        head: Vertex,
        tail: Vertex,
    }

    #[test]
    fn test_struct_clone_and_eq() {
        let a = Vertex(Point2D { x: 1.0, y: 2.0 });
        let b = a.clone();
        assert_eq!(a, b);
        let c = Vertex(Point2D { x: 1.0, y: 3.0 });
        assert!(a != c);
    }

    #[test]
    fn test_struct_into() {
        let v = Vertex(Point2D { x: 4.0, y: 5.0 });
        let inner: Point2D = v.into();
        assert_eq!(Point2D { x: 4.0, y: 5.0 }, inner);
    }

    #[test]
    fn test_struct_debug() {
        let v = Vertex(Point2D { x: 0.0, y: 0.0 });
        let dbg = format!("{:?}", v);
        assert!(dbg.contains("Vertex"));
        assert!(dbg.contains("Point2D"));
    }

    #[test]
    fn test_struct_wrapping_vec() {
        let n = Numbers(vec![1, 2, 3]);
        let m = n.clone();
        assert_eq!(n, m);
        let inner: Vec<u32> = n.into();
        assert_eq!(vec![1, 2, 3], inner);
    }

    #[test]
    fn test_struct_composes_in_outer_struct() {
        let c1 = Container {
            head: Vertex(Point2D { x: 0.0, y: 0.0 }),
            tail: Vertex(Point2D { x: 1.0, y: 1.0 }),
        };
        let c2 = c1.clone();
        assert_eq!(c1, c2);
    }
}

#[cfg(test)]
mod tests_newtype_validated {
    use std::error::Error;

    newtype_validated!(Probability, ProbabilityError, f32, |x: &f32| (0.0..=1.0)
        .contains(x));

    fn is_even(x: &u32) -> bool {
        x.is_multiple_of(2)
    }
    newtype_validated!(EvenU32, EvenU32Error, u32, is_even);

    newtype_validated!(NonEmpty, NonEmptyError, String, |s: &String| !s.is_empty());

    #[derive(Debug, Clone, PartialEq)]
    pub struct Range {
        pub lo: i32,
        pub hi: i32,
    }
    newtype_validated!(SortedRange, SortedRangeError, Range, |r: &Range| r.lo
        <= r.hi);

    #[test]
    fn test_closure_validator_valid() {
        let p = Probability::new(0.5).unwrap();
        let inner: f32 = p.into();
        assert!((inner - 0.5).abs() < f32::EPSILON);
    }

    #[test]
    fn test_closure_validator_invalid() {
        assert_eq!(Err(ProbabilityError), Probability::new(2.0));
        assert_eq!(Err(ProbabilityError), Probability::new(-0.1));
    }

    #[test]
    fn test_closure_validator_boundaries() {
        assert!(Probability::new(0.0).is_ok());
        assert!(Probability::new(1.0).is_ok());
    }

    #[test]
    fn test_function_path_validator() {
        assert!(EvenU32::new(4).is_ok());
        assert_eq!(Err(EvenU32Error), EvenU32::new(5));
    }

    #[test]
    fn test_string_validator() {
        assert!(NonEmpty::new("hello".to_string()).is_ok());
        assert_eq!(Err(NonEmptyError), NonEmpty::new(String::new()));
    }

    #[test]
    fn test_struct_validator() {
        assert!(SortedRange::new(Range { lo: 1, hi: 5 }).is_ok());
        assert_eq!(
            Err(SortedRangeError),
            SortedRange::new(Range { lo: 5, hi: 1 })
        );
    }

    #[test]
    fn test_tryfrom_valid() {
        let p: Probability = (0.5_f32).try_into().unwrap();
        let inner: f32 = p.into();
        assert!((inner - 0.5).abs() < f32::EPSILON);
    }

    #[test]
    fn test_tryfrom_invalid() {
        let r: Result<Probability, _> = (2.0_f32).try_into();
        assert_eq!(Err(ProbabilityError), r);
    }

    #[test]
    fn test_error_traits() {
        let e = ProbabilityError;
        let dbg = format!("{:?}", e);
        assert!(dbg.contains("ProbabilityError"));
        let disp = format!("{}", e);
        assert_eq!("invalid Probability value", disp);
        let copy = e;
        assert_eq!(e, copy);
        let _src: Option<&(dyn Error + 'static)> = e.source();
    }

    #[test]
    fn test_clone_and_eq_on_validated_value() {
        let a = Probability::new(0.25).unwrap();
        let b = a.clone();
        assert_eq!(a, b);
    }
}

#[cfg(test)]
mod tests_pointer_sized_ints {
    use std::str::FromStr;

    newtype!(UsizeId, usize);
    newtype_from!(UsizeId, usize);

    newtype_ord!(UsizeOrd, usize);
    newtype_from!(UsizeOrd, usize);

    newtype_unit!(UsizeUnit, usize);
    newtype_from!(UsizeUnit, usize);

    newtype!(UsizeOnly, usize);
    newtype_from_only!(UsizeOnly, usize);

    newtype!(UsizeStr, usize);
    newtype_fromstr!(UsizeStr, usize);

    newtype!(IsizeId, isize);
    newtype_from!(IsizeId, isize);

    newtype_ord!(IsizeOrd, isize);
    newtype_from!(IsizeOrd, isize);

    newtype_unit!(IsizeUnit, isize);
    newtype_from!(IsizeUnit, isize);

    newtype!(IsizeOnly, isize);
    newtype_from_only!(IsizeOnly, isize);

    newtype!(IsizeStr, isize);
    newtype_fromstr!(IsizeStr, isize);

    #[test]
    fn test_usize_basics() {
        let a = UsizeId::from(42);
        let b = UsizeId::from(42);
        let c = UsizeId::from(7);
        assert_eq!(a, b);
        assert!(a != c);
        let n: usize = a.into();
        assert_eq!(42, n);
    }

    #[test]
    fn test_usize_ord() {
        let a = UsizeOrd::from(1);
        let b = UsizeOrd::from(2);
        assert!(a < b);
    }

    #[test]
    fn test_usize_unit_arithmetic() {
        let a = UsizeUnit::from(10);
        let b = UsizeUnit::from(3);
        let c = a + b;
        let n: usize = c.into();
        assert_eq!(13, n);
    }

    #[test]
    fn test_usize_fromstr_via_newtype_from() {
        assert_eq!(Ok(UsizeId(99)), UsizeId::from_str("99"));
        assert!(UsizeId::from_str("nope").is_err());
    }

    #[test]
    fn test_usize_from_only() {
        let a = UsizeOnly::from(5);
        let n: usize = a.into();
        assert_eq!(5, n);
    }

    #[test]
    fn test_usize_fromstr_only() {
        let a = UsizeStr::from_str("123").unwrap();
        let n: usize = a.into();
        assert_eq!(123, n);
    }

    #[test]
    fn test_isize_basics() {
        let a = IsizeId::from(-42);
        let b = IsizeId::from(-42);
        let c = IsizeId::from(7);
        assert_eq!(a, b);
        assert!(a != c);
        let n: isize = a.into();
        assert_eq!(-42, n);
    }

    #[test]
    fn test_isize_ord() {
        let a = IsizeOrd::from(-1);
        let b = IsizeOrd::from(2);
        assert!(a < b);
    }

    #[test]
    fn test_isize_unit_arithmetic() {
        let a = IsizeUnit::from(10);
        let b = IsizeUnit::from(-3);
        let c = a + b;
        let n: isize = c.into();
        assert_eq!(7, n);
    }

    #[test]
    fn test_isize_fromstr_via_newtype_from() {
        assert_eq!(Ok(IsizeId(-99)), IsizeId::from_str("-99"));
        assert!(IsizeId::from_str("nope").is_err());
    }

    #[test]
    fn test_isize_from_only() {
        let a = IsizeOnly::from(-5);
        let n: isize = a.into();
        assert_eq!(-5, n);
    }

    #[test]
    fn test_isize_fromstr_only() {
        let a = IsizeStr::from_str("-123").unwrap();
        let n: isize = a.into();
        assert_eq!(-123, n);
    }
}

#[cfg(test)]
mod tests_layout {
    use std::mem::{align_of, size_of};

    newtype!(LayoutI8, i8);
    newtype!(LayoutU64, u64);
    newtype!(LayoutI128, i128);
    newtype!(LayoutF32, f32);
    newtype!(LayoutF64, f64);
    newtype!(LayoutString, String);

    #[derive(Debug)]
    #[allow(dead_code)]
    struct Wide {
        a: u64,
        b: u32,
    }
    newtype!(LayoutStruct, Wide);

    #[test]
    fn test_size_matches_inner() {
        assert_eq!(size_of::<i8>(), size_of::<LayoutI8>());
        assert_eq!(size_of::<u64>(), size_of::<LayoutU64>());
        assert_eq!(size_of::<i128>(), size_of::<LayoutI128>());
        assert_eq!(size_of::<f32>(), size_of::<LayoutF32>());
        assert_eq!(size_of::<f64>(), size_of::<LayoutF64>());
        assert_eq!(size_of::<String>(), size_of::<LayoutString>());
        assert_eq!(size_of::<Wide>(), size_of::<LayoutStruct>());
    }

    #[test]
    fn test_align_matches_inner() {
        assert_eq!(align_of::<i8>(), align_of::<LayoutI8>());
        assert_eq!(align_of::<u64>(), align_of::<LayoutU64>());
        assert_eq!(align_of::<i128>(), align_of::<LayoutI128>());
        assert_eq!(align_of::<f32>(), align_of::<LayoutF32>());
        assert_eq!(align_of::<f64>(), align_of::<LayoutF64>());
        assert_eq!(align_of::<String>(), align_of::<LayoutString>());
        assert_eq!(align_of::<Wide>(), align_of::<LayoutStruct>());
    }
}

#[cfg(test)]
mod tests_newtype_array {
    newtype_array!(Mac, u8, 6);
    newtype_array!(Floats, f32, 4);
    newtype_array!(Names, String, 2);
    newtype_array!(Empty, u8, 0);

    #[derive(Debug, Clone, PartialEq)]
    pub struct Tag(pub u32);
    newtype_array!(Tags, Tag, 3);

    #[test]
    fn test_index_usize() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        assert_eq!(1, m[0]);
        assert_eq!(6, m[5]);
    }

    #[test]
    fn test_index_mut_usize() {
        let mut m = Mac([0; 6]);
        m[0] = 42;
        m[5] = 7;
        assert_eq!(42, m[0]);
        assert_eq!(7, m[5]);
    }

    #[test]
    fn test_range_index() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let s: &[u8] = &m[1..3];
        assert_eq!(&[2u8, 3], s);
        let s: &[u8] = &m[..];
        assert_eq!(&[1u8, 2, 3, 4, 5, 6], s);
        let s: &[u8] = &m[2..];
        assert_eq!(&[3u8, 4, 5, 6], s);
        let s: &[u8] = &m[..=1];
        assert_eq!(&[1u8, 2], s);
    }

    #[test]
    fn test_range_index_mut() {
        let mut m = Mac([1, 2, 3, 4, 5, 6]);
        m[1..3].copy_from_slice(&[20, 30]);
        assert_eq!(20, m[1]);
        assert_eq!(30, m[2]);
    }

    #[test]
    fn test_iter_inherent() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let sum: u32 = m.iter().map(|&x| x as u32).sum();
        assert_eq!(21, sum);
    }

    #[test]
    fn test_iter_mut_inherent() {
        let mut m = Mac([1, 2, 3, 4, 5, 6]);
        for x in m.iter_mut() {
            *x *= 2;
        }
        assert_eq!(2, m[0]);
        assert_eq!(12, m[5]);
    }

    #[test]
    fn test_into_iter_ref() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let sum: u32 = (&m).into_iter().map(|&x| x as u32).sum();
        assert_eq!(21, sum);
    }

    #[test]
    fn test_into_iter_owned() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let v: Vec<u8> = m.into_iter().collect();
        assert_eq!(vec![1u8, 2, 3, 4, 5, 6], v);
    }

    #[test]
    fn test_for_loop_ref() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let mut total: u32 = 0;
        for x in &m {
            total += *x as u32;
        }
        assert_eq!(21, total);
    }

    #[test]
    fn test_for_loop_mut() {
        let mut m = Mac([1, 2, 3, 4, 5, 6]);
        for x in &mut m {
            *x += 1;
        }
        assert_eq!(2, m[0]);
        assert_eq!(7, m[5]);
    }

    #[test]
    fn test_len_and_is_empty() {
        let m = Mac([0; 6]);
        assert_eq!(6, m.len());
        assert!(!m.is_empty());

        let e = Empty([]);
        assert_eq!(0, e.len());
        assert!(e.is_empty());
    }

    #[test]
    fn test_as_array() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let a: &[u8; 6] = m.as_array();
        assert_eq!(&[1u8, 2, 3, 4, 5, 6], a);
    }

    #[test]
    fn test_as_array_mut() {
        let mut m = Mac([0; 6]);
        m.as_array_mut()[0] = 9;
        assert_eq!(9, m[0]);
    }

    #[test]
    fn test_into_array() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let a: [u8; 6] = m.into();
        assert_eq!([1u8, 2, 3, 4, 5, 6], a);
    }

    #[test]
    fn test_as_ref_slice() {
        let m = Mac([1, 2, 3, 4, 5, 6]);
        let s: &[u8] = m.as_ref();
        assert_eq!(&[1u8, 2, 3, 4, 5, 6], s);
    }

    #[test]
    fn test_as_mut_slice() {
        let mut m = Mac([1, 2, 3, 4, 5, 6]);
        let s: &mut [u8] = m.as_mut();
        s[0] = 99;
        assert_eq!(99, m[0]);
    }

    #[test]
    fn test_eq_and_hash_for_int_array() {
        use std::collections::HashSet;
        let a = Mac([1, 2, 3, 4, 5, 6]);
        let b = Mac([1, 2, 3, 4, 5, 6]);
        let c = Mac([6, 5, 4, 3, 2, 1]);
        assert_eq!(a, b);
        assert!(a != c);
        let mut set: HashSet<Mac> = HashSet::new();
        set.insert(a);
        assert!(set.contains(&b));
        assert!(!set.contains(&c));
    }

    #[test]
    fn test_copy_for_int_array() {
        let a = Mac([1, 2, 3, 4, 5, 6]);
        let b = a;
        let c = a;
        assert_eq!(a, b);
        assert_eq!(a, c);
    }

    #[test]
    fn test_float_array_partialeq() {
        let a = Floats([1.0, 2.0, 3.0, 4.0]);
        let b = Floats([1.0, 2.0, 3.0, 4.0]);
        let c = Floats([1.0, 2.0, 3.0, 5.0]);
        assert!(a == b);
        assert!(a != c);
    }

    #[test]
    fn test_string_array() {
        let n = Names(["alice".into(), "bob".into()]);
        let m = n.clone();
        assert_eq!(n, m);
        assert_eq!("alice", n[0]);
        assert_eq!("bob", n[1]);
    }

    #[test]
    fn test_generic_struct_array() {
        let t = Tags([Tag(1), Tag(2), Tag(3)]);
        let u = t.clone();
        assert_eq!(t, u);
        assert_eq!(Tag(2), t[1]);
    }

    #[test]
    fn test_empty_array_iter() {
        let e = Empty([]);
        let count = e.iter().count();
        assert_eq!(0, count);
        let count = e.into_iter().count();
        assert_eq!(0, count);
    }
}

#[cfg(test)]
mod tests_newtype_array_deref {
    newtype_array_deref!(Buf, u8, 4);

    #[test]
    fn test_deref_slice_methods() {
        let b = Buf([1, 2, 3, 4]);
        assert_eq!(Some(&1u8), b.first());
        assert_eq!(Some(&4u8), b.last());
        assert!(b.contains(&3));
        assert!(!b.contains(&99));
    }

    #[test]
    fn test_deref_mut_slice_method() {
        let mut b = Buf([1, 2, 3, 4]);
        b.fill(0);
        assert_eq!([0u8, 0, 0, 0], *b.as_array());
    }

    #[test]
    fn test_deref_target_is_slice() {
        let b = Buf([10, 20, 30, 40]);
        let s: &[u8] = &b;
        assert_eq!(&[10u8, 20, 30, 40], s);
    }

    #[test]
    fn test_deref_does_not_break_inherent_iter() {
        let b = Buf([1, 2, 3, 4]);
        let sum: u32 = b.iter().map(|&x| x as u32).sum();
        assert_eq!(10, sum);
    }
}

#[cfg(test)]
mod tests_newtype_array_layout {
    use std::mem::{align_of, size_of};

    newtype_array!(LU8x6, u8, 6);
    newtype_array!(LU64x4, u64, 4);
    newtype_array!(LF32x3, f32, 3);
    newtype_array_deref!(LDU8x4, u8, 4);

    #[test]
    fn test_size_matches_inner() {
        assert_eq!(size_of::<[u8; 6]>(), size_of::<LU8x6>());
        assert_eq!(size_of::<[u64; 4]>(), size_of::<LU64x4>());
        assert_eq!(size_of::<[f32; 3]>(), size_of::<LF32x3>());
        assert_eq!(size_of::<[u8; 4]>(), size_of::<LDU8x4>());
    }

    #[test]
    fn test_align_matches_inner() {
        assert_eq!(align_of::<[u8; 6]>(), align_of::<LU8x6>());
        assert_eq!(align_of::<[u64; 4]>(), align_of::<LU64x4>());
        assert_eq!(align_of::<[f32; 3]>(), align_of::<LF32x3>());
        assert_eq!(align_of::<[u8; 4]>(), align_of::<LDU8x4>());
    }
}