Initial import of cast-0.2.3. am: 80f5cd0831

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/cast/+/1620970

Change-Id: I78a2d041a9d87a825dc275be4c2977e1b0afbc89

12 files changed, 1024 insertions, 0 deletions

diff --git a/.cargo_vcs_info.json b/.cargo_vcs_info.json
new file mode 100644
index 0000000..13f1433
--- /dev/null
+++ b/.cargo_vcs_info.json
@@ -0,0 +1,5 @@
+{
+  "git": {
+    "sha1": "74cec5dcf2014ecfe7cb05837b147cbb4f49024e"
+  }
+}
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..dcc96f3
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+*.rs.bk
+Cargo.lock
+target/*
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..6da2fc0
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,35 @@
+language: rust
+
+matrix:
+  include:
+    # MSRV
+    - env: TARGET=x86_64-unknown-linux-gnu
+      rust: 1.13.0
+
+      # 32-bit
+    - env: TARGET=i686-unknown-linux-musl
+    - env: TARGET=x86_64-unknown-linux-gnu
+
+before_install: set -e
+
+install:
+  - bash ci/install.sh
+
+script:
+  - bash ci/script.sh
+
+after_script: set +e
+
+cache: cargo
+
+before_cache:
+  - chmod -R a+r $HOME/.cargo
+
+branches:
+  only:
+    - staging
+    - trying
+
+notifications:
+  email:
+    on_success: never
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..eb26758
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,54 @@
+# Change Log
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+
+## [v0.2.3] - 2018-11-17
+
+### Changed
+
+- Documented the guaranteed MRSV to be 1.13
+- The `x128` feature now works on *stable* Rust 1.26+
+
+### Fixed
+
+- Overflow and underflow checks when casting a float to an unsigned integer
+
+## [v0.2.2] - 2017-05-07
+
+### Fixed
+
+- UB in the checked cast from `f32` to `u128`.
+
+## [v0.2.1] - 2017-05-06
+
+### Added
+
+- Support for 128-bit integers, behind the `x128` Cargo feature (nightly
+  needed).
+
+## [v0.2.0] - 2017-02-08
+
+### Added
+
+- Now `cast::Error` implements the `std::error::Error` trait among other traits
+  like `Display`, `Clone`, etc.
+
+### Changed
+
+- [breaking-change] This crate now depends on the `std` crate by default but you
+  can make it `no_std` by opting out of the `std` Cargo feature.
+
+## v0.1.0 - 2016-02-07
+
+Initial release
+
+[Unreleased]: https://github.com/japaric/cast.rs/compare/v0.2.3...HEAD
+[v0.2.3]: https://github.com/japaric/cast.rs/compare/v0.2.2...v0.2.3
+[v0.2.2]: https://github.com/japaric/cast.rs/compare/v0.2.1...v0.2.2
+[v0.2.1]: https://github.com/japaric/cast.rs/compare/v0.2.0...v0.2.1
+[v0.2.0]: https://github.com/japaric/cast.rs/compare/v0.1.0...v0.2.0
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..40df4af
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,31 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+name = "cast"
+version = "0.2.3"
+authors = ["Jorge Aparicio <jorge@japaric.io>"]
+build = "build.rs"
+description = "Ergonomic, checked cast functions for primitive types"
+documentation = "https://docs.rs/cast"
+keywords = ["checked", "cast", "primitive", "integer", "float"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/japaric/cast.rs"
+[dev-dependencies.quickcheck]
+version = "0.9.0"
+[build-dependencies.rustc_version]
+version = "0.2.3"
+
+[features]
+default = ["std"]
+std = []
+x128 = []
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..6e95860
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,25 @@
+[package]
+authors = ["Jorge Aparicio <jorge@japaric.io>"]
+build = "build.rs"
+description = "Ergonomic, checked cast functions for primitive types"
+documentation = "https://docs.rs/cast"
+keywords = ["checked", "cast", "primitive", "integer", "float"]
+license = "MIT OR Apache-2.0"
+name = "cast"
+repository = "https://github.com/japaric/cast.rs"
+version = "0.2.3"
+
+[features]
+# Assume we should use `std` unless asked to do otherwise.
+default = ["std"]
+# Enable this to get a std::error::Error impl for convenient use with other
+# libraries.
+std = []
+# Enable this for i128/u128 support
+x128 = []
+
+[build-dependencies]
+rustc_version = "0.2.3"
+
+[dev-dependencies]
+quickcheck = "0.9.0"
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3ed32f1
--- /dev/null
+++ b/README.md
@@ -0,0 +1,44 @@
+[![crates.io](https://img.shields.io/crates/d/cast.svg)](https://crates.io/crates/cast)
+[![crates.io](https://img.shields.io/crates/v/cast.svg)](https://crates.io/crates/cast)
+
+# `cast`
+
+> Ergonomic, checked cast functions for primitive types
+
+``` rust
+extern crate cast;
+
+// `u8` and `u16` are checked cast functions, use them to cast from any numeric
+// primitive to `u8`/`u16` respectively
+use cast::{u8, u16, Error};
+
+// Infallible operations, like integer promotion, are equivalent to a normal
+// cast with `as`
+assert_eq!(u16(0u8), 0u16);
+
+// Everything else will return a `Result` depending on the success of the
+// operation
+assert_eq!(u8(0u16), Ok(0u8));
+assert_eq!(u8(256u16), Err(Error::Overflow));
+assert_eq!(u8(-1i8), Err(Error::Underflow));
+assert_eq!(u8(1. / 0.), Err(Error::Infinite));
+assert_eq!(u8(0. / 0.), Err(Error::NaN));
+```
+
+## [API docs](https://docs.rs/cast)
+
+## License
+
+Licensed under either of
+
+- Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or
+  http://www.apache.org/licenses/LICENSE-2.0)
+- MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally submitted
+for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
+dual licensed as above, without any additional terms or conditions.
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..2aa9f5b
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,8 @@
+extern crate rustc_version;
+
+fn main() {
+    let vers = rustc_version::version().unwrap();
+    if vers.major == 1 && vers.minor >= 26 {
+        println!("cargo:rustc-cfg=stable_i128")
+    }
+}
diff --git a/ci/install.sh b/ci/install.sh
new file mode 100644
index 0000000..3c41921
--- /dev/null
+++ b/ci/install.sh
@@ -0,0 +1,9 @@
+set -euxo pipefail
+
+main() {
+    if [ $TARGET != x86_64-unknown-linux-gnu ]; then
+        rustup target add $TARGET
+    fi
+}
+
+main
diff --git a/ci/script.sh b/ci/script.sh
new file mode 100644
index 0000000..12b2619
--- /dev/null
+++ b/ci/script.sh
@@ -0,0 +1,43 @@
+set -euxo pipefail
+
+main() {
+    # not MSRV
+    if [ $TRAVIS_RUST_VERSION != 1.13.0 ]; then
+        cargo check --target $TARGET --no-default-features
+
+        cargo test --features x128 --target $TARGET
+        cargo test --features x128 --target $TARGET --release
+    else
+        cargo build --target $TARGET --no-default-features
+        cargo build --target $TARGET
+    fi
+}
+
+# fake Travis variables to be able to run this on a local machine
+if [ -z ${TRAVIS_BRANCH-} ]; then
+    TRAVIS_BRANCH=staging
+fi
+
+if [ -z ${TRAVIS_PULL_REQUEST-} ]; then
+    TRAVIS_PULL_REQUEST=false
+fi
+
+if [ -z ${TRAVIS_RUST_VERSION-} ]; then
+    case $(rustc -V) in
+        *nightly*)
+            TRAVIS_RUST_VERSION=nightly
+            ;;
+        *beta*)
+            TRAVIS_RUST_VERSION=beta
+            ;;
+        *)
+            TRAVIS_RUST_VERSION=stable
+            ;;
+    esac
+fi
+
+if [ -z ${TARGET-} ]; then
+    TARGET=$(rustc -Vv | grep host | cut -d ' ' -f2)
+fi
+
+main
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..4a8efe9
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,546 @@
+//! Ergonomic, checked cast functions for primitive types
+//!
+//! This crate provides one checked cast function for each numeric primitive.
+//! Use these functions to perform a cast from any other numeric primitive:
+//!
+//! ```
+//! extern crate cast;
+//!
+//! use cast::{u8, u16, Error};
+//!
+//! # fn main() {
+//! // Infallible operations, like integer promotion, are equivalent to a normal
+//! // cast with `as`
+//! assert_eq!(u16(0u8), 0u16);
+//!
+//! // Everything else will return a `Result` depending on the success of the
+//! // operation
+//! assert_eq!(u8(0u16), Ok(0u8));
+//! assert_eq!(u8(256u16), Err(Error::Overflow));
+//! assert_eq!(u8(-1i8), Err(Error::Underflow));
+//! assert_eq!(u8(1. / 0.), Err(Error::Infinite));
+//! assert_eq!(u8(0. / 0.), Err(Error::NaN));
+//! # }
+//! ```
+//!
+//! There are no namespace problems between these functions, the "primitive
+//! modules" in `core`/`std` and the built-in primitive types, so all them can
+//! be in the same scope:
+//!
+//! ```
+//! extern crate cast;
+//!
+//! use std::u8;
+//! use cast::{u8, u16};
+//!
+//! # fn main() {
+//! // `u8` as a type
+//! let x: u8 = 0;
+//! // `u8` as a module
+//! let y = u16(u8::MAX);
+//! // `u8` as a function
+//! let z = u8(y).unwrap();
+//! # }
+//! ```
+//!
+//! The checked cast functionality is also usable with type aliases via the
+//! `cast` static method:
+//!
+//! ```
+//! extern crate cast;
+//!
+//! use std::os::raw::c_ulonglong;
+//! // NOTE avoid shadowing `std::convert::From` - cf. rust-lang/rfcs#1311
+//! use cast::From as _0;
+//!
+//! # fn main() {
+//! assert_eq!(c_ulonglong::cast(0u8), 0u64);
+//! # }
+//! ```
+//!
+//! This crate also provides a `From` trait that can be used, for example,
+//! to create a generic function that accepts any type that can be infallibly
+//! casted to `u32`.
+//!
+//! ```
+//! extern crate cast;
+//!
+//! fn to_u32<T>(x: T) -> u32
+//!     // reads as: "where u32 can be casted from T with output u32"
+//!     where u32: cast::From<T, Output=u32>,
+//! {
+//!     cast::u32(x)
+//! }
+//!
+//! # fn main() {
+//! assert_eq!(to_u32(0u8), 0u32);
+//! assert_eq!(to_u32(1u16), 1u32);
+//! assert_eq!(to_u32(2u32), 2u32);
+//!
+//! // to_u32(-1i32);  // Compile error
+//! # }
+//! ```
+//!
+//! ## Minimal Supported Rust Version
+//!
+//! This crate is guaranteed to compile on stable Rust 1.13 and up. It *might* compile on older
+//! versions but that may change in any new patch release.
+//!
+//! ## Building without `std`
+//!
+//! This crate can be used without Rust's `std` crate by declaring it as
+//! follows in your `Cargo.toml`:
+//!
+//! ``` toml
+//! cast = { version = "*", default-features = false }
+//! ```
+
+#![deny(missing_docs)]
+#![deny(warnings)]
+#![allow(const_err)]
+#![cfg_attr(not(feature = "std"), no_std)]
+#![cfg_attr(all(feature = "x128", not(stable_i128)), feature(i128_type, i128))]
+
+#[cfg(feature = "std")]
+extern crate core;
+
+#[cfg(test)]
+#[macro_use]
+extern crate quickcheck;
+
+use core::fmt;
+#[cfg(feature = "std")]
+use std::error;
+
+#[cfg(test)]
+mod test;
+
+/// Cast errors
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum Error {
+    /// Infinite value casted to a type that can only represent finite values
+    Infinite,
+    /// NaN value casted to a type that can't represent a NaN value
+    NaN,
+    /// Source value is greater than the maximum value that the destination type
+    /// can hold
+    Overflow,
+    /// Source value is smaller than the minimum value that the destination type
+    /// can hold
+    Underflow,
+}
+
+impl Error {
+    /// A private helper function that implements `description`, because
+    /// `description` is only available when we have `std` enabled.
+    fn description_helper(&self) -> &str {
+        match *self {
+            Error::Infinite => "Cannot store infinite value in finite type",
+            Error::NaN => "Cannot store NaN in type which does not support it",
+            Error::Overflow => "Overflow during numeric conversion",
+            Error::Underflow => "Underflow during numeric conversion",
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.description_helper())
+    }
+}
+
+#[cfg(feature = "std")]
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        self.description_helper()
+    }
+}
+
+/// The "cast from" operation
+pub trait From<Src> {
+    /// The result of the cast operation: either `Self` or `Result<Self, Error>`
+    type Output;
+
+    /// Checked cast from `Src` to `Self`
+    fn cast(Src) -> Self::Output;
+}
+
+macro_rules! fns {
+    ($($ty:ident),+) => {
+        $(
+            /// Checked cast function
+            #[inline]
+            pub fn $ty<T>(x: T) -> <$ty as From<T>>::Output
+                where $ty: From<T>
+            {
+                <$ty as From<T>>::cast(x)
+            }
+         )+
+    }
+}
+
+fns!(f32, f64, i8, i16, i32, i64, isize, u8, u16, u32, u64, usize);
+
+#[cfg(feature = "x128")]
+fns!(i128, u128);
+
+/// `$dst` can hold any value of `$src`
+macro_rules! promotion {
+    ($($src:ty => $($dst: ty),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                    type Output = $dst;
+
+                    #[inline]
+                    fn cast(src: $src) -> $dst {
+                        src as $dst
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+/// `$dst` can hold any positive value of `$src`
+macro_rules! half_promotion {
+    ($($src:ty => $($dst:ty),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                    type Output = Result<$dst, Error>;
+
+                    #[inline]
+                    fn cast(src: $src) -> Self::Output {
+                        if src < 0 {
+                            Err(Error::Underflow)
+                        } else {
+                            Ok(src as $dst)
+                        }
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+/// From an unsigned `$src` to a smaller `$dst`
+macro_rules! from_unsigned {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                    type Output = Result<$dst, Error>;
+
+                    #[inline]
+                    fn cast(src: $src) -> Self::Output {
+                        use core::$dst;
+
+                        if src > $dst::MAX as $src {
+                            Err(Error::Overflow)
+                        } else {
+                            Ok(src as $dst)
+                        }
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+/// From a signed `$src` to a smaller `$dst`
+macro_rules! from_signed {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                    type Output = Result<$dst, Error>;
+
+                    #[inline]
+                    fn cast(src: $src) -> Self::Output {
+                        use core::$dst;
+
+                        Err(if src < $dst::MIN as $src {
+                            Error::Underflow
+                        } else if src > $dst::MAX as $src {
+                            Error::Overflow
+                        } else {
+                            return Ok(src as $dst);
+                        })
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+/// From a float `$src` to an integer `$dst`
+macro_rules! from_float {
+    ($($src:ident, $usrc:ident => $($dst:ident),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                    type Output = Result<$dst, Error>;
+
+                    #[inline]
+                    fn cast(src: $src) -> Self::Output {
+                        use core::{$dst, $src};
+
+                        Err(if src != src {
+                            Error::NaN
+                        } else if src == $src::INFINITY ||
+                            src == $src::NEG_INFINITY {
+                            Error::Infinite
+                        } else if {
+                            // we subtract 1 ULP (unit of least precision) here because some
+                            // lossy conversions like `u64::MAX as f64` round *up* and we want
+                            // to avoid this evaluating to false in that case
+                            use core::mem::transmute;
+                            let max = unsafe {
+                                transmute::<_, $src>(transmute::<_, $usrc>($dst::MAX as $src) - 1)
+                            };
+                            src > max
+                        } {
+                            Error::Overflow
+                        } else if $dst::MIN == 0 {
+                            // when casting to unsigned integer, negative values close to 0 but
+                            // larger than 1.0 should be truncated to 0; this behavior matches
+                            // casting from a float to a signed integer
+                            if src <= -1.0 {
+                                Error::Underflow
+                            } else {
+                                return Ok(src as $dst);
+                            }
+                        } else if src < $dst::MIN as $src {
+                            Error::Underflow
+                        } else  {
+                            return Ok(src as $dst);
+                        })
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+/// From a float `$src` to an integer `$dst`, where $dst is large enough to contain
+/// all values of `$src`. We can't ever overflow here
+#[cfg(feature = "x128")]
+macro_rules! from_float_dst {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        $(
+            $(
+                impl From<$src> for $dst {
+                     type Output = Result<$dst, Error>;
+
+                    #[inline]
+                    #[allow(unused_comparisons)]
+                    fn cast(src: $src) -> Self::Output {
+                        use core::{$dst, $src};
+
+                        Err(if src != src {
+                            Error::NaN
+                        } else if src == $src::INFINITY ||
+                            src == $src::NEG_INFINITY {
+                            Error::Infinite
+                        } else if ($dst::MIN == 0) && src <= -1.0 {
+                            Error::Underflow
+                        } else {
+                            return Ok(src as $dst);
+                        })
+                    }
+                }
+            )+
+        )+
+    }
+}
+
+// PLAY TETRIS! ;-)
+
+#[cfg(target_pointer_width = "32")]
+mod _32 {
+    use {Error, From};
+
+    // Signed
+    promotion! {
+        i8    => f32, f64, i8, i16, i32, isize, i64;
+        i16   => f32, f64,     i16, i32, isize, i64;
+        i32   => f32, f64,          i32, isize, i64;
+        isize => f32, f64,          i32, isize, i64;
+        i64   => f32, f64,                      i64;
+    }
+
+    half_promotion! {
+        i8    =>                                     u8, u16, u32, usize, u64;
+        i16   =>                                         u16, u32, usize, u64;
+        i32   =>                                              u32, usize, u64;
+        isize =>                                              u32, usize, u64;
+        i64   =>                                                          u64;
+    }
+
+    from_signed! {
+
+        i16   =>           i8,                       u8;
+        i32   =>           i8, i16,                  u8, u16;
+        isize =>           i8, i16,                  u8, u16;
+        i64   =>           i8, i16, i32, isize,      u8, u16, u32, usize;
+    }
+
+    // Unsigned
+    promotion! {
+        u8    => f32, f64,     i16, i32, isize, i64, u8, u16, u32, usize, u64;
+        u16   => f32, f64,          i32, isize, i64,     u16, u32, usize, u64;
+        u32   => f32, f64,                      i64,          u32, usize, u64;
+        usize => f32, f64,                      i64,          u32, usize, u64;
+        u64   => f32, f64,                                                u64;
+    }
+
+    from_unsigned! {
+        u8    =>           i8;
+        u16   =>           i8, i16,                  u8;
+        u32   =>           i8, i16, i32, isize,      u8, u16;
+        usize =>           i8, i16, i32, isize,      u8, u16;
+        u64   =>           i8, i16, i32, isize, i64, u8, u16, u32, usize;
+    }
+
+    // Float
+    promotion! {
+        f32   => f32, f64;
+        f64   =>      f64;
+    }
+
+    from_float! {
+        f32, u32 =>        i8, i16, i32, isize, i64, u8, u16, u32, usize, u64;
+        f64, u64 =>        i8, i16, i32, isize, i64, u8, u16, u32, usize, u64;
+    }
+}
+
+#[cfg(target_pointer_width = "64")]
+mod _64 {
+    use {Error, From};
+
+    // Signed
+    promotion! {
+        i8    => f32, f64, i8, i16, i32, i64, isize;
+        i16   => f32, f64,     i16, i32, i64, isize;
+        i32   => f32, f64,          i32, i64, isize;
+        i64   => f32, f64,               i64, isize;
+        isize => f32, f64,               i64, isize;
+    }
+
+    half_promotion! {
+        i8    =>                                     u8, u16, u32, u64, usize;
+        i16   =>                                         u16, u32, u64, usize;
+        i32   =>                                              u32, u64, usize;
+        i64   =>                                                   u64, usize;
+        isize =>                                                   u64, usize;
+    }
+
+    from_signed! {
+
+        i16   =>           i8,                       u8;
+        i32   =>           i8, i16,                  u8, u16;
+        i64   =>           i8, i16, i32,             u8, u16, u32;
+        isize =>           i8, i16, i32,             u8, u16, u32;
+    }
+
+    // Unsigned
+    promotion! {
+        u8    => f32, f64,     i16, i32, i64, isize, u8, u16, u32, u64, usize;
+        u16   => f32, f64,          i32, i64, isize,     u16, u32, u64, usize;
+        u32   => f32, f64,               i64, isize,          u32, u64, usize;
+        u64   => f32, f64,                                         u64, usize;
+        usize => f32, f64,                                         u64, usize;
+    }
+
+    from_unsigned! {
+        u8    =>           i8;
+        u16   =>           i8, i16,                  u8;
+        u32   =>           i8, i16, i32,             u8, u16;
+        u64   =>           i8, i16, i32, i64, isize, u8, u16, u32;
+        usize =>           i8, i16, i32, i64, isize, u8, u16, u32;
+    }
+
+    // Float
+    promotion! {
+        f32  => f32, f64;
+        f64  =>      f64;
+    }
+
+    from_float! {
+        f32, u32  =>       i8, i16, i32, i64, isize, u8, u16, u32, u64, usize;
+        f64, u64  =>       i8, i16, i32, i64, isize, u8, u16, u32, u64, usize;
+    }
+}
+
+#[cfg(feature = "x128")]
+mod _x128 {
+    use {Error, From};
+
+    // Signed
+    promotion! {
+        i8    =>                              i128;
+        i16   =>                              i128;
+        i32   =>                              i128;
+        i64   =>                              i128;
+        isize =>                              i128;
+        i128  => f32, f64,                    i128;
+    }
+
+    half_promotion! {
+        i8    =>                                                              u128;
+        i16   =>                                                              u128;
+        i32   =>                                                              u128;
+        i64   =>                                                              u128;
+        isize =>                                                              u128;
+        i128  =>                                                              u128;
+    }
+
+    from_signed! {
+        i128  =>           i8, i16, i32, i64,       isize, u8, u16, u32, u64,       usize;
+    }
+
+    // Unsigned
+    promotion! {
+        u8    =>                              i128,                           u128;
+        u16   =>                              i128,                           u128;
+        u32   =>                              i128,                           u128;
+        u64   =>                              i128,                           u128;
+        usize =>                              i128,                           u128;
+        u128  =>      f64,                                                    u128;
+    }
+
+    from_unsigned! {
+        u128 => f32,       i8, i16, i32, i64, i128, isize, u8, u16, u32, u64,       usize;
+    }
+
+    // Float
+    from_float! {
+        f32, u32  => i128;
+        f64, u64  => i128, u128;
+    }
+
+    from_float_dst! {
+        f32       =>       u128;
+    }
+}
+
+// The missing piece
+impl From<f64> for f32 {
+    type Output = Result<f32, Error>;
+
+    #[inline]
+    fn cast(src: f64) -> Self::Output {
+        use core::{f32, f64};
+
+        if src != src || src == f64::INFINITY || src == f64::NEG_INFINITY {
+            Ok(src as f32)
+        } else if src < f32::MIN as f64 {
+            Err(Error::Underflow)
+        } else if src > f32::MAX as f64 {
+            Err(Error::Overflow)
+        } else {
+            Ok(src as f32)
+        }
+    }
+}
diff --git a/src/test.rs b/src/test.rs
new file mode 100644
index 0000000..6b619ab
--- /dev/null
+++ b/src/test.rs
@@ -0,0 +1,221 @@
+// If `src` can be promoted to `$dst`, then it must be Ok to cast `dst` back to
+// `$src`
+macro_rules! promote_and_back {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        mod demoting_to {
+            $(
+                mod $src {
+                    mod from {
+                        use From;
+
+                        $(
+                            quickcheck! {
+                                fn $dst(src: $src) -> bool {
+                                    $src::cast($dst::cast(src)).is_ok()
+                                }
+                            }
+                         )+
+                    }
+                }
+             )+
+        }
+    }
+}
+
+#[cfg(target_pointer_width = "32")]
+promote_and_back! {
+    i8    => f32, f64,     i16, i32, isize, i64                          ;
+    i16   => f32, f64,          i32, isize, i64                          ;
+    i32   => f32, f64,                      i64                          ;
+    isize => f32, f64,                      i64                          ;
+    i64   => f32, f64                                                    ;
+    u8    => f32, f64,     i16, i32, isize, i64,     u16, u32, usize, u64;
+    u16   => f32, f64,          i32, isize, i64,          u32, usize, u64;
+    u32   => f32, f64,                      i64,                      u64;
+    usize => f32, f64,                      i64,                      u64;
+    u64   => f32, f64                                                    ;
+}
+
+#[cfg(target_pointer_width = "64")]
+promote_and_back! {
+    i8    => f32, f64,     i16, i32, i64, isize                          ;
+    i16   => f32, f64,          i32, i64, isize                          ;
+    i32   => f32, f64,               i64, isize                          ;
+    i64   => f32, f64                                                    ;
+    isize => f32, f64                                                    ;
+    u8    => f32, f64,     i16, i32, i64, isize,     u16, u32, u64, usize;
+    u16   => f32, f64,          i32, i64, isize,          u32, u64, usize;
+    u32   => f32, f64,               i64, isize,               u64, usize;
+    u64   => f32, f64                                                    ;
+    usize => f32, f64                                                    ;
+}
+
+// TODO uncomment this once quickcheck supports Arbitrary for i128/u128
+// https://github.com/BurntSushi/quickcheck/issues/162
+/*#[cfg(feature = "x128")]
+promote_and_back! {
+    i8    =>           i128      ;
+    i16   =>           i128      ;
+    i32   =>           i128      ;
+    isize =>           i128      ;
+    i64   =>           i128      ;
+    i128  => f32, f64            ;
+    u8    =>           i128, u128;
+    u16   =>           i128, u128;
+    u32   =>           i128, u128;
+    usize =>           i128, u128;
+    u64   =>           i128, u128;
+    u128  => f32, f64            ;
+}*/
+
+// If it's Ok to cast `src` to `$dst`, it must also be Ok to cast `dst` back to
+// `$src`
+macro_rules! symmetric_cast_between {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        mod symmetric_cast_between {
+            $(
+                mod $src {
+                    mod and {
+                        use quickcheck::TestResult;
+
+                        use From;
+
+                        $(
+                            quickcheck! {
+                                fn $dst(src: $src) -> TestResult {
+                                    if let Ok(dst) = $dst::cast(src) {
+                                        TestResult::from_bool(
+                                            $src::cast(dst).is_ok())
+                                    } else {
+                                        TestResult::discard()
+                                    }
+                                }
+                            }
+                         )+
+                    }
+                }
+             )+
+        }
+    }
+}
+
+#[cfg(target_pointer_width = "32")]
+symmetric_cast_between! {
+    u8    =>           i8                      ;
+    u16   =>           i8, i16                 ;
+    u32   =>           i8, i16, i32            ;
+    usize =>           i8, i16, i32            ;
+    u64   =>           i8, i16, i32, i64, isize;
+}
+
+#[cfg(target_pointer_width = "64")]
+symmetric_cast_between! {
+    u8    =>           i8                      ;
+    u16   =>           i8, i16                 ;
+    u32   =>           i8, i16, i32            ;
+    u64   =>           i8, i16, i32, i64, isize;
+    usize =>           i8, i16, i32, i64, isize;
+}
+
+// TODO uncomment this once quickcheck supports Arbitrary for i128/u128
+// https://github.com/BurntSushi/quickcheck/issues/162
+/*#[cfg(feature = "x128")]
+symmetric_cast_between! {
+    u128  => i8, i16, i32, isize, i64, i128;
+}*/
+
+macro_rules! from_float {
+    ($($src:ident => $($dst:ident),+);+;) => {
+        $(
+            mod $src {
+                mod inf {
+                    mod to {
+                        use {Error, From};
+
+                        $(
+                            #[test]
+                            fn $dst() {
+                                let _0: $src = 0.;
+                                let _1: $src = 1.;
+                                let inf = _1 / _0;
+                                let neg_inf = -_1 / _0;
+
+                                assert_eq!($dst::cast(inf),
+                                           Err(Error::Infinite));
+                                assert_eq!($dst::cast(neg_inf),
+                                           Err(Error::Infinite));
+                            }
+                         )+
+                    }
+                }
+
+                mod nan {
+                    mod to {
+                        use {Error, From};
+
+                        $(
+                            #[test]
+                            fn $dst() {
+                                let _0: $src = 0.;
+                                let nan = _0 / _0;
+
+                                assert_eq!($dst::cast(nan),
+                                           Err(Error::NaN));
+                            }
+                         )+
+                    }
+                }
+            }
+         )+
+    }
+}
+
+from_float! {
+    f32 => i8, i16, i32, i64, isize, u8, u16, u32, u64, usize;
+    f64 => i8, i16, i32, i64, isize, u8, u16, u32, u64, usize;
+}
+
+// TODO uncomment this once quickcheck supports Arbitrary for i128/u128
+// https://github.com/BurntSushi/quickcheck/issues/162
+/*#[cfg(feature = "x128")]
+from_float! {
+    f32 => i128, u128;
+    f64 => i128, u128;
+}*/
+
+#[test]
+#[cfg(feature = "x128")]
+fn test_fl_conversion() {
+    use u128;
+    assert_eq!(u128(42.0f32), Ok(42));
+}
+
+#[test]
+fn gh16() {
+    assert_eq!(super::u64(-0.01_f64), Ok(0));
+    assert_eq!(super::u64(-0.99_f32), Ok(0));
+
+    assert_eq!(super::u32(-0.99_f64), Ok(0));
+    assert_eq!(super::u32(-0.01_f32), Ok(0));
+
+    assert_eq!(super::u64(0.01_f64), Ok(0));
+    assert_eq!(super::u64(0.99_f32), Ok(0));
+
+    assert_eq!(super::u32(0.99_f64), Ok(0));
+    assert_eq!(super::u32(0.01_f32), Ok(0));
+}
+
+#[test]
+fn gh15() {
+    assert_eq!(super::u32(32_f32.exp2()), Err(super::Error::Overflow));
+    assert_eq!(super::u32(32_f64.exp2()), Err(super::Error::Overflow));
+
+    assert_eq!(super::u64(64_f32.exp2()), Err(super::Error::Overflow));
+    assert_eq!(super::u64(64_f64.exp2()), Err(super::Error::Overflow));
+
+    assert_eq!(super::u8(8_f32.exp2()), Err(super::Error::Overflow));
+    assert_eq!(super::u8(8_f64.exp2()), Err(super::Error::Overflow));
+
+    assert_eq!(super::u16(16_f32.exp2()), Err(super::Error::Overflow));
+    assert_eq!(super::u16(16_f64.exp2()), Err(super::Error::Overflow));
+}