New version: 0.9.

.travis.yml

@@ -0,0 +1,6 @@
+language: rust
+rust:
+  - 1.0.0
+  - stable
+  - beta
+  - nightly

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "version_check"
-version = "0.1.5"
+version = "0.9.0"
 authors = ["Sergio Benitez <sb@sergio.bz>"]
 description = "Tiny crate to check the version of the installed/running rustc."
 documentation = "https://docs.rs/version_check/"

README.md

@@ -1,5 +1,9 @@
 # version\_check
 
+[![Build Status](https://travis-ci.com/SergioBenitez/version_check.svg?branch=master)](https://travis-ci.com/SergioBenitez/version_check)
+[![Current Crates.io Version](https://img.shields.io/crates/v/version_check.svg)](https://crates.io/crates/version_check)
+[![rustdocs on docs.rs](https://docs.rs/version_check/badge.svg)](https://docs.rs/version_check)
+
 This tiny crate checks that the running or installed `rustc` meets some version
 requirements. The version is queried by calling the Rust compiler with
 `--version`. The path to the compiler is determined first via the `RUSTC`
@@ -12,54 +16,57 @@ Add to your `Cargo.toml` file, typically as a build dependency:
 
 ```toml
 [build-dependencies]
-version_check = "0.1"
+version_check = "0.9"
 ```
 
 `version_check` is compatible and compiles with Rust 1.0.0 and beyond.
 
 ## Examples
 
-Check that the running compiler is a nightly release:
+Set a `cfg` flag in `build.rs` if the running compiler was determined to be
+at least version `1.13.0`:
 
 ```rust
-extern crate version_check;
+extern crate version_check as rustc;
 
-match version_check::is_nightly() {
+if rustc::is_min_version("1.13.0").unwrap_or(false) {
-    Some(true) => "running a nightly",
+    println!("cargo:rustc-cfg=question_mark_operator");
-    Some(false) => "not nightly",
+}
-    None => "couldn't figure it out"
+```
+
+Check that the running compiler was released on or after `2018-12-18`:
+
+```rust
+extern crate version_check as rustc;
+
+match rustc::is_min_date("2018-12-18") {
+    Some(true) => "Yep! It's recent!",
+    Some(false) => "No, it's older.",
+    None => "Couldn't determine the rustc version."
 };
 ```
 
-Check that the running compiler is at least version `1.13.0`:
+Check that the running compiler supports feature flags:
 
 ```rust
-extern crate version_check;
+extern crate version_check as rustc;
 
-match version_check::is_min_version("1.13.0") {
+match rustc::is_feature_flaggable() {
-    Some((true, version)) => format!("Yes! It's: {}", version),
+    Some(true) => "Yes! It's a dev or nightly release!",
-    Some((false, version)) => format!("No! {} is too old!", version),
+    Some(false) => "No, it's stable or beta.",
-    None => "couldn't figure it out".into()
+    None => "Couldn't determine the rustc version."
 };
 ```
 
-Check that the running compiler was released on or after `2016-12-18`:
+See the [rustdocs](https://docs.rs/version_check) for more examples and complete
-
+documentation.
-```rust
-extern crate version_check;
-
-match version_check::is_min_date("2016-12-18") {
-    Some((true, date)) => format!("Yes! It's: {}", date),
-    Some((false, date)) => format!("No! {} is too long ago!", date),
-    None => "couldn't figure it out".into()
-};
-```
 
 ## Alternatives
 
-This crate is dead simple with no dependencies. If you need something more and
+This crate is dead simple with no dependencies. If you need something more
-don't care about panicking if the version cannot be obtained or adding
+and don't care about panicking if the version cannot be obtained, or if you
-dependencies, see [rustc_version](https://crates.io/crates/rustc_version).
+don't mind adding dependencies, see
+[rustc_version](https://crates.io/crates/rustc_version).
 
 ## License
 

src/channel.rs

@@ -0,0 +1,192 @@
+use std::fmt;
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+enum Kind {
+    Dev,
+    Nightly,
+    Beta,
+    Stable,
+}
+
+/// Release channel: "dev", "nightly", "beta", or "stable".
+#[derive(Debug, PartialEq, Eq, Copy, Clone)]
+pub struct Channel(Kind);
+
+impl Channel {
+    /// Reads the release channel of the running compiler. If it cannot be
+    /// determined (see the [top-level documentation](crate)), returns `None`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// match Channel::read() {
+    ///     Some(c) => format!("The channel is: {}", c),
+    ///     None => format!("Failed to read the release channel.")
+    /// };
+    /// ```
+    pub fn read() -> Option<Channel> {
+        ::get_version_and_date()
+            .and_then(|(version, _)| version)
+            .and_then(|version| Channel::parse(&version))
+    }
+
+    /// Parse a Rust release channel from a Rust release version string (of the
+    /// form `major[.minor[.patch[-channel]]]`). Returns `None` if `version` is
+    /// not a valid Rust version string.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let dev = Channel::parse("1.3.0-dev").unwrap();
+    /// assert!(dev.is_dev());
+    ///
+    /// let nightly = Channel::parse("1.42.2-nightly").unwrap();
+    /// assert!(nightly.is_nightly());
+    ///
+    /// let beta = Channel::parse("1.32.0-beta").unwrap();
+    /// assert!(beta.is_beta());
+    ///
+    /// let stable = Channel::parse("1.4.0").unwrap();
+    /// assert!(stable.is_stable());
+    /// ```
+    pub fn parse(version: &str) -> Option<Channel> {
+        if version.contains("-dev") {
+            Some(Channel(Kind::Dev))
+        } else if version.contains("-nightly") {
+            Some(Channel(Kind::Nightly))
+        } else if version.contains("-beta") {
+            Some(Channel(Kind::Beta))
+        } else if !version.contains("-") {
+            Some(Channel(Kind::Stable))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the name of the release channel.
+    fn as_str(&self) -> &'static str {
+        match self.0 {
+            Kind::Dev => "dev",
+            Kind::Beta => "beta",
+            Kind::Nightly => "nightly",
+            Kind::Stable => "stable",
+        }
+    }
+
+    /// Returns `true` if this channel supports feature flags. In other words,
+    /// returns `true` if the channel is either `dev` or `nightly`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let dev = Channel::parse("1.3.0-dev").unwrap();
+    /// assert!(dev.supports_features());
+    ///
+    /// let nightly = Channel::parse("1.42.2-nightly").unwrap();
+    /// assert!(nightly.supports_features());
+    ///
+    /// let beta = Channel::parse("1.32.0-beta").unwrap();
+    /// assert!(!beta.supports_features());
+    ///
+    /// let stable = Channel::parse("1.4.0").unwrap();
+    /// assert!(!stable.supports_features());
+    /// ```
+    pub fn supports_features(&self) -> bool {
+        match self.0 {
+            Kind::Dev | Kind::Nightly => true,
+            Kind::Beta | Kind::Stable => false
+        }
+    }
+
+    /// Returns `true` if this channel is `dev` and `false` otherwise.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let dev = Channel::parse("1.3.0-dev").unwrap();
+    /// assert!(dev.is_dev());
+    ///
+    /// let stable = Channel::parse("1.0.0").unwrap();
+    /// assert!(!stable.is_dev());
+    /// ```
+    pub fn is_dev(&self) -> bool {
+        match self.0 {
+            Kind::Dev => true,
+            _ => false
+        }
+    }
+
+    /// Returns `true` if this channel is `nightly` and `false` otherwise.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let nightly = Channel::parse("1.3.0-nightly").unwrap();
+    /// assert!(nightly.is_nightly());
+    ///
+    /// let stable = Channel::parse("1.0.0").unwrap();
+    /// assert!(!stable.is_nightly());
+    /// ```
+    pub fn is_nightly(&self) -> bool {
+        match self.0 {
+            Kind::Nightly => true,
+            _ => false
+        }
+    }
+
+    /// Returns `true` if this channel is `beta` and `false` otherwise.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let beta = Channel::parse("1.3.0-beta").unwrap();
+    /// assert!(beta.is_beta());
+    ///
+    /// let stable = Channel::parse("1.0.0").unwrap();
+    /// assert!(!stable.is_beta());
+    /// ```
+    pub fn is_beta(&self) -> bool {
+        match self.0 {
+            Kind::Beta => true,
+            _ => false
+        }
+    }
+
+    /// Returns `true` if this channel is `stable` and `false` otherwise.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Channel;
+    ///
+    /// let stable = Channel::parse("1.0.0").unwrap();
+    /// assert!(stable.is_stable());
+    ///
+    /// let beta = Channel::parse("1.3.0-beta").unwrap();
+    /// assert!(!beta.is_stable());
+    /// ```
+    pub fn is_stable(&self) -> bool {
+        match self.0 {
+            Kind::Stable => true,
+            _ => false
+        }
+    }
+}
+
+impl fmt::Display for Channel {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.as_str())
+    }
+}

src/date.rs

@@ -0,0 +1,146 @@
+use std::fmt;
+
+/// Release date including year, month, and day.
+#[derive(Debug, PartialEq, Eq, Copy, Clone, PartialOrd, Ord)]
+pub struct Date(u32);
+
+impl Date {
+    /// Reads the release date of the running compiler. If it cannot be
+    /// determined (see the [top-level documentation](crate)), returns `None`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Date;
+    ///
+    /// match Date::read() {
+    ///     Some(d) => format!("The release date is: {}", d),
+    ///     None => format!("Failed to read the release date.")
+    /// };
+    /// ```
+    pub fn read() -> Option<Date> {
+        ::get_version_and_date()
+            .and_then(|(_, date)| date)
+            .and_then(|date| Date::parse(&date))
+    }
+
+    /// Return the original (YYYY, MM, DD).
+    fn to_ymd(&self) -> (u8, u8, u8) {
+        let y = self.0 >> 9;
+        let m = (self.0 << 23) >> 28;
+        let d = (self.0 << 27) >> 27;
+        (y as u8, m as u8, d as u8)
+    }
+
+    /// Parse a release date of the form `%Y-%m-%d`. Returns `None` if `date` is
+    /// not in `%Y-%m-%d` format.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Date;
+    ///
+    /// let date = Date::parse("2016-04-20").unwrap();
+    ///
+    /// assert!(date.at_least("2016-01-10"));
+    /// assert!(date.at_most("2016-04-20"));
+    /// assert!(date.exactly("2016-04-20"));
+    ///
+    /// assert!(Date::parse("March 13, 2018").is_none());
+    /// assert!(Date::parse("1-2-3-4-5").is_none());
+    /// ```
+    pub fn parse(date: &str) -> Option<Date> {
+        let ymd: Vec<u32> = date.split("-")
+            .filter_map(|s| s.parse::<u32>().ok())
+            .collect();
+
+        if ymd.len() != 3 {
+            return None
+        }
+
+        let (y, m, d) = (ymd[0], ymd[1], ymd[2]);
+        Some(Date((y << 9) | (m << 5) | d))
+    }
+
+    /// Returns `true` if `self` occurs on or after `date`.
+    ///
+    /// If `date` occurs before `self`, or if `date` is not in `%Y-%m-%d`
+    /// format, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Date;
+    ///
+    /// let date = Date::parse("2020-01-01").unwrap();
+    ///
+    /// assert!(date.at_least("2019-12-31"));
+    /// assert!(date.at_least("2020-01-01"));
+    /// assert!(date.at_least("2014-04-31"));
+    ///
+    /// assert!(!date.at_least("2020-01-02"));
+    /// assert!(!date.at_least("2024-08-18"));
+    /// ```
+    pub fn at_least(&self, date: &str) -> bool {
+        Date::parse(date)
+            .map(|date| self >= &date)
+            .unwrap_or(false)
+    }
+
+    /// Returns `true` if `self` occurs on or before `date`.
+    ///
+    /// If `date` occurs after `self`, or if `date` is not in `%Y-%m-%d`
+    /// format, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Date;
+    ///
+    /// let date = Date::parse("2020-01-01").unwrap();
+    ///
+    /// assert!(date.at_most("2020-01-01"));
+    /// assert!(date.at_most("2020-01-02"));
+    /// assert!(date.at_most("2024-08-18"));
+    ///
+    /// assert!(!date.at_most("2019-12-31"));
+    /// assert!(!date.at_most("2014-04-31"));
+    /// ```
+    pub fn at_most(&self, date: &str) -> bool {
+        Date::parse(date)
+            .map(|date| self <= &date)
+            .unwrap_or(false)
+    }
+
+    /// Returns `true` if `self` occurs exactly on `date`.
+    ///
+    /// If `date` is not exactly `self`, or if `date` is not in `%Y-%m-%d`
+    /// format, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Date;
+    ///
+    /// let date = Date::parse("2020-01-01").unwrap();
+    ///
+    /// assert!(date.exactly("2020-01-01"));
+    ///
+    /// assert!(!date.exactly("2019-12-31"));
+    /// assert!(!date.exactly("2014-04-31"));
+    /// assert!(!date.exactly("2020-01-02"));
+    /// assert!(!date.exactly("2024-08-18"));
+    /// ```
+    pub fn exactly(&self, date: &str) -> bool {
+        Date::parse(date)
+            .map(|date| self == &date)
+            .unwrap_or(false)
+    }
+}
+
+impl fmt::Display for Date {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let (y, m, d) = self.to_ymd();
+        write!(f, "{}-{}-{}", y, m, d)
+    }
+}

src/lib.rs

@@ -4,96 +4,96 @@
 //! `RUSTC` environment variable. If it is not set, then `rustc` is used. If
 //! that fails, no determination is made, and calls return `None`.
 //!
-//! # Example
+//! # Examples
 //!
-//! Check that the running compiler is a nightly release:
+//! Set a `cfg` flag in `build.rs` if the running compiler was determined to be
+//! at least version `1.13.0`:
 //!
 //! ```rust
-//! extern crate version_check;
+//! extern crate version_check as rustc;
 //!
-//! match version_check::is_nightly() {
+//! if rustc::is_min_version("1.13.0").unwrap_or(false) {
-//!     Some(true) => "running a nightly",
+//!     println!("cargo:rustc-cfg=question_mark_operator");
-//!     Some(false) => "not nightly",
+//! }
-//!     None => "couldn't figure it out"
+//! ```
+//!
+//! See [`is_max_version`] or [`is_exact_version`] to check if the compiler
+//! is _at most_ or _exactly_ a certain version.
+//!
+//! Check that the running compiler was released on or after `2018-12-18`:
+//!
+//! ```rust
+//! extern crate version_check as rustc;
+//!
+//! match rustc::is_min_date("2018-12-18") {
+//!     Some(true) => "Yep! It's recent!",
+//!     Some(false) => "No, it's older.",
+//!     None => "Couldn't determine the rustc version."
 //! };
 //! ```
 //!
-//! Check that the running compiler is at least version `1.13.0`:
+//! See [`is_max_date`] or [`is_exact_date`] to check if the compiler was
+//! released _prior to_ or _exactly on_ a certain date.
+//!
+//! Check that the running compiler supports feature flags:
 //!
 //! ```rust
-//! extern crate version_check;
+//! extern crate version_check as rustc;
 //!
-//! match version_check::is_min_version("1.13.0") {
+//! match rustc::is_feature_flaggable() {
-//!     Some((true, version)) => format!("Yes! It's: {}", version),
+//!     Some(true) => "Yes! It's a dev or nightly release!",
-//!     Some((false, version)) => format!("No! {} is too old!", version),
+//!     Some(false) => "No, it's stable or beta.",
-//!     None => "couldn't figure it out".into()
+//!     None => "Couldn't determine the rustc version."
 //! };
 //! ```
 //!
-//! Check that the running compiler was released on or after `2016-12-18`:
+//! Check that the running compiler is on the stable channel:
 //!
 //! ```rust
-//! extern crate version_check;
+//! extern crate version_check as rustc;
 //!
-//! match version_check::is_min_date("2016-12-18") {
+//! match rustc::Channel::read() {
-//!     Some((true, date)) => format!("Yes! It's: {}", date),
+//!     Some(c) if c.is_stable() => format!("Yes! It's stable."),
-//!     Some((false, date)) => format!("No! {} is too long ago!", date),
+//!     Some(c) => format!("No, the channel {} is not stable.", c),
-//!     None => "couldn't figure it out".into()
+//!     None => format!("Couldn't determine the rustc version.")
 //! };
 //! ```
 //!
+//! To interact with the version, release date, and release channel as structs,
+//! use [`Version`], [`Date`], and [`Channel`], respectively. The [`triple()`]
+//! function returns all three values efficiently.
+//!
 //! # Alternatives
 //!
 //! This crate is dead simple with no dependencies. If you need something more
-//! and don't care about panicking if the version cannot be obtained or adding
+//! and don't care about panicking if the version cannot be obtained, or if you
-//! dependencies, see [rustc_version](https://crates.io/crates/rustc_version).
+//! don't mind adding dependencies, see
+//! [rustc_version](https://crates.io/crates/rustc_version).
+
+#![allow(deprecated)]
+
+mod version;
+mod channel;
+mod date;
 
 use std::env;
 use std::process::Command;
 
-// Convert a string of %Y-%m-%d to a single u32 maintaining ordering.
+#[doc(inline)] pub use version::*;
-fn str_to_ymd(ymd: &str) -> Option<u32> {
+#[doc(inline)] pub use channel::*;
-    let ymd: Vec<u32> = ymd.split("-").filter_map(|s| s.parse::<u32>().ok()).collect();
+#[doc(inline)] pub use date::*;
-    if ymd.len() != 3 {
-        return None
-    }
 
-    let (y, m, d) = (ymd[0], ymd[1], ymd[2]);
+/// Parses (version, date) as available from rustc version string.
-    Some((y << 9) | (m << 5) | d)
-}
-
-// Convert a string with prefix major-minor-patch to a single u64 maintaining
-// ordering. Assumes none of the components are > 1048576.
-fn str_to_mmp(mmp: &str) -> Option<u64> {
-    let mut mmp: Vec<u16> = mmp.split('-')
-        .nth(0)
-        .unwrap_or("")
-        .split('.')
-        .filter_map(|s| s.parse::<u16>().ok())
-        .collect();
-
-    if mmp.is_empty() {
-        return None
-    }
-
-    while mmp.len() < 3 {
-        mmp.push(0);
-    }
-
-    let (maj, min, patch) = (mmp[0] as u64, mmp[1] as u64, mmp[2] as u64);
-    Some((maj << 32) | (min << 16) | patch)
-}
-
-/// Returns (version, date) as available.
 fn version_and_date_from_rustc_version(s: &str) -> (Option<String>, Option<String>) {
     let last_line = s.lines().last().unwrap_or(s);
     let mut components = last_line.trim().split(" ");
     let version = components.nth(1);
-    let date = components.nth(1).map(|s| s.trim_right().trim_right_matches(")"));
+    let date = components.filter(|c| c.ends_with(')')).next()
+        .map(|s| s.trim_right().trim_right_matches(")").trim_left().trim_left_matches('('));
     (version.map(|s| s.to_string()), date.map(|s| s.to_string()))
 }
 
-/// Returns (version, date) as available.
+/// Returns (version, date) as available from `rustc --version`.
 fn get_version_and_date() -> Option<(Option<String>, Option<String>)> {
     env::var("RUSTC").ok()
         .and_then(|rustc| Command::new(rustc).arg("--version").output().ok())
@@ -102,154 +102,187 @@ fn get_version_and_date() -> Option<(Option<String>, Option<String>)> {
         .map(|s| version_and_date_from_rustc_version(&s))
 }
 
-/// Checks that the running or installed `rustc` was released no earlier than
+/// Reads the triple of [`Version`], [`Channel`], and [`Date`] of the installed
+/// or running `rustc`.
+///
+/// If any attribute cannot be determined (see the [top-level
+/// documentation](crate)), returns `None`.
+///
+/// To obtain only one of three attributes, use [`Version::read()`],
+/// [`Channel::read()`], or [`Date::read()`].
+pub fn triple() -> Option<(Version, Channel, Date)> {
+    let (version_str, date_str) = match get_version_and_date() {
+        Some((Some(version), Some(date))) => (version, date),
+        _ => return None
+    };
+
+    // Can't use `?` or `try!` for `Option` in 1.0.0.
+    match Version::parse(&version_str) {
+        Some(version) => match Channel::parse(&version_str) {
+            Some(channel) => match Date::parse(&date_str) {
+                Some(date) => Some((version, channel, date)),
+                _ => None,
+            },
+            _ => None,
+        },
+        _ => None
+    }
+}
+
+/// Checks that the running or installed `rustc` was released **on or after**
 /// some date.
 ///
 /// The format of `min_date` must be YYYY-MM-DD. For instance: `2016-12-20` or
 /// `2017-01-09`.
 ///
 /// If the date cannot be retrieved or parsed, or if `min_date` could not be
-/// parsed, returns `None`. Otherwise returns a tuple where the first value is
+/// parsed, returns `None`. Otherwise returns `true` if the installed `rustc`
-/// `true` if the installed `rustc` is at least from `min_date` and the second
+/// was release on or after `min_date` and `false` otherwise.
-/// value is the date (in YYYY-MM-DD) of the installed `rustc`.
+pub fn is_min_date(min_date: &str) -> Option<bool> {
-pub fn is_min_date(min_date: &str) -> Option<(bool, String)> {
+    match (Date::read(), Date::parse(min_date)) {
-    if let Some((_, Some(actual_date_str))) = get_version_and_date() {
+        (Some(rustc_date), Some(min_date)) => Some(rustc_date >= min_date),
-        str_to_ymd(&actual_date_str)
+        _ => None
-            .and_then(|actual| str_to_ymd(min_date).map(|min| (min, actual)))
-            .map(|(min, actual)| (actual >= min, actual_date_str))
-    } else {
-        None
     }
 }
 
-/// Checks that the running or installed `rustc` is at least some minimum
+/// Checks that the running or installed `rustc` was released **on or before**
+/// some date.
+///
+/// The format of `max_date` must be YYYY-MM-DD. For instance: `2016-12-20` or
+/// `2017-01-09`.
+///
+/// If the date cannot be retrieved or parsed, or if `max_date` could not be
+/// parsed, returns `None`. Otherwise returns `true` if the installed `rustc`
+/// was release on or before `max_date` and `false` otherwise.
+pub fn is_max_date(max_date: &str) -> Option<bool> {
+    match (Date::read(), Date::parse(max_date)) {
+        (Some(rustc_date), Some(max_date)) => Some(rustc_date <= max_date),
+        _ => None
+    }
+}
+
+/// Checks that the running or installed `rustc` was released **exactly** on
+/// some date.
+///
+/// The format of `date` must be YYYY-MM-DD. For instance: `2016-12-20` or
+/// `2017-01-09`.
+///
+/// If the date cannot be retrieved or parsed, or if `date` could not be parsed,
+/// returns `None`. Otherwise returns `true` if the installed `rustc` was
+/// release on `date` and `false` otherwise.
+pub fn is_exact_date(date: &str) -> Option<bool> {
+    match (Date::read(), Date::parse(date)) {
+        (Some(rustc_date), Some(date)) => Some(rustc_date == date),
+        _ => None
+    }
+}
+
+/// Checks that the running or installed `rustc` is **at least** some minimum
 /// version.
 ///
 /// The format of `min_version` is a semantic version: `1.3.0`, `1.15.0-beta`,
 /// `1.14.0`, `1.16.0-nightly`, etc.
 ///
 /// If the version cannot be retrieved or parsed, or if `min_version` could not
-/// be parsed, returns `None`. Otherwise returns a tuple where the first value
+/// be parsed, returns `None`. Otherwise returns `true` if the installed `rustc`
-/// is `true` if the installed `rustc` is at least `min_version` and the second
+/// is at least `min_version` and `false` otherwise.
-/// value is the version (semantic) of the installed `rustc`.
+pub fn is_min_version(min_version: &str) -> Option<bool> {
-pub fn is_min_version(min_version: &str) -> Option<(bool, String)> {
+    match (Version::read(), Version::parse(min_version)) {
-    if let Some((Some(actual_version_str), _)) = get_version_and_date() {
+        (Some(rustc_ver), Some(min_ver)) => Some(rustc_ver >= min_ver),
-        str_to_mmp(&actual_version_str)
+        _ => None
-            .and_then(|actual| str_to_mmp(min_version).map(|min| (min, actual)))
-            .map(|(min, actual)| (actual >= min, actual_version_str))
-    } else {
-        None
     }
 }
 
-fn version_channel_is(channel: &str) -> Option<bool> {
+/// Checks that the running or installed `rustc` is **at most** some maximum
-    get_version_and_date()
+/// version.
-        .and_then(|(version_str_opt, _)|  version_str_opt)
-        .map(|version_str| version_str.contains(channel))
-}
-
-/// Determines whether the running or installed `rustc` is on the nightly
-/// channel.
 ///
-/// If the version could not be determined, returns `None`. Otherwise returns
+/// The format of `max_version` is a semantic version: `1.3.0`, `1.15.0-beta`,
-/// `Some(true)` if the running version is a nightly release, and `Some(false)`
+/// `1.14.0`, `1.16.0-nightly`, etc.
-/// otherwise.
-pub fn is_nightly() -> Option<bool> {
-    version_channel_is("nightly")
-}
-
-/// Determines whether the running or installed `rustc` is on the beta channel.
 ///
-/// If the version could not be determined, returns `None`. Otherwise returns
+/// If the version cannot be retrieved or parsed, or if `max_version` could not
-/// `Some(true)` if the running version is a beta release, and `Some(false)`
+/// be parsed, returns `None`. Otherwise returns `true` if the installed `rustc`
-/// otherwise.
+/// is at most `max_version` and `false` otherwise.
-pub fn is_beta() -> Option<bool> {
+pub fn is_max_version(max_version: &str) -> Option<bool> {
-    version_channel_is("beta")
+    match (Version::read(), Version::parse(max_version)) {
+        (Some(rustc_ver), Some(max_ver)) => Some(rustc_ver <= max_ver),
+        _ => None
+    }
 }
 
-/// Determines whether the running or installed `rustc` is on the dev channel.
+/// Checks that the running or installed `rustc` is **exactly** some version.
 ///
-/// If the version could not be determined, returns `None`. Otherwise returns
+/// The format of `version` is a semantic version: `1.3.0`, `1.15.0-beta`,
-/// `Some(true)` if the running version is a dev release, and `Some(false)`
+/// `1.14.0`, `1.16.0-nightly`, etc.
-/// otherwise.
+///
-pub fn is_dev() -> Option<bool> {
+/// If the version cannot be retrieved or parsed, or if `version` could not be
-    version_channel_is("dev")
+/// parsed, returns `None`. Otherwise returns `true` if the installed `rustc` is
+/// exactly `version` and `false` otherwise.
+pub fn is_exact_version(version: &str) -> Option<bool> {
+    match (Version::read(), Version::parse(version)) {
+        (Some(rustc_ver), Some(version)) => Some(rustc_ver == version),
+        _ => None
+    }
 }
 
-/// Determines whether the running or installed `rustc` supports feature flags.
+/// Checks whether the running or installed `rustc` supports feature flags.
+///
 /// In other words, if the channel is either "nightly" or "dev".
 ///
 /// If the version could not be determined, returns `None`. Otherwise returns
-/// `Some(true)` if the running version supports features, and `Some(false)`
+/// `true` if the running version supports feature flags and `false` otherwise.
-/// otherwise.
+pub fn is_feature_flaggable() -> Option<bool> {
-pub fn supports_features() -> Option<bool> {
+    Channel::read().map(|c| c.supports_features())
-    match is_nightly() {
-        b@Some(true) => b,
-        _ => is_dev()
-    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::version_and_date_from_rustc_version;
-    use super::str_to_mmp;
 
-    macro_rules! check_mmp {
+    macro_rules! check_parse {
-        ($string:expr => ($x:expr, $y:expr, $z:expr)) => (
+        ($s:expr => $v:expr, $d:expr) => (
-            if let Some(mmp) = str_to_mmp($string) {
+            if let (Some(v), d) = version_and_date_from_rustc_version($s) {
-                let expected = $x << 32 | $y << 16 | $z;
+                let e_d: Option<&str> = $d.into();
-                if mmp != expected {
+                assert_eq!((v, d), ($v.into(), e_d.map(|s| s.into())));
-                    panic!("{:?} didn't parse as {}.{}.{}.", $string, $x, $y, $z);
-                }
-            } else {
-                panic!("{:?} didn't parse for mmp testing.", $string);
-            }
-        )
-    }
-
-    macro_rules! check_version {
-        ($s:expr => ($x:expr, $y:expr, $z:expr)) => (
-            if let (Some(version_str), _) = version_and_date_from_rustc_version($s) {
-                check_mmp!(&version_str => ($x, $y, $z));
             } else {
                 panic!("{:?} didn't parse for version testing.", $s);
             }
         )
     }
 
-    #[test]
-    fn test_str_to_mmp() {
-        check_mmp!("1.18.0" => (1, 18, 0));
-        check_mmp!("1.19.0" => (1, 19, 0));
-        check_mmp!("1.19.0-nightly" => (1, 19, 0));
-        check_mmp!("1.12.2349" => (1, 12, 2349));
-        check_mmp!("0.12" => (0, 12, 0));
-        check_mmp!("1.12.5" => (1, 12, 5));
-        check_mmp!("1.12" => (1, 12, 0));
-        check_mmp!("1" => (1, 0, 0));
-    }
-
     #[test]
     fn test_version_parse() {
-        check_version!("rustc 1.18.0" => (1, 18, 0));
+        check_parse!("rustc 1.18.0" => "1.18.0", None);
-        check_version!("rustc 1.8.0" => (1, 8, 0));
+        check_parse!("rustc 1.8.0" => "1.8.0", None);
-        check_version!("rustc 1.20.0-nightly" => (1, 20, 0));
+        check_parse!("rustc 1.20.0-nightly" => "1.20.0-nightly", None);
-        check_version!("rustc 1.20" => (1, 20, 0));
+        check_parse!("rustc 1.20" => "1.20", None);
-        check_version!("rustc 1.3" => (1, 3, 0));
+        check_parse!("rustc 1.3" => "1.3", None);
-        check_version!("rustc 1" => (1, 0, 0));
+        check_parse!("rustc 1" => "1", None);
-        check_version!("rustc 1.2.5.6" => (1, 2, 5));
+        check_parse!("rustc 1.5.1-beta" => "1.5.1-beta", None);
-        check_version!("rustc 1.5.1-beta" => (1, 5, 1));
-        check_version!("rustc 1.20.0-nightly (d84693b93 2017-07-09)" => (1, 20, 0));
-        check_version!("rustc 1.20.0 (d84693b93 2017-07-09)" => (1, 20, 0));
-        check_version!("rustc 1.20.0 (2017-07-09)" => (1, 20, 0));
-        check_version!("rustc 1.20.0-dev (2017-07-09)" => (1, 20, 0));
 
-        check_version!("warning: invalid logging spec 'warning', ignoring it
+        // Because of 1.0.0, we can't use Option<T>: From<T>.
-                        rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)" => (1, 30, 0));
+        check_parse!("rustc 1.20.0 (2017-07-09)"
-        check_version!("warning: invalid logging spec 'warning', ignoring it\n
+                     => "1.20.0", Some("2017-07-09"));
-                        rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)" => (1, 30, 0));
+
-        check_version!("warning: invalid logging spec 'warning', ignoring it
+        check_parse!("rustc 1.20.0-dev (2017-07-09)"
-                        warning: something else went wrong
+                     => "1.20.0-dev", Some("2017-07-09"));
-                        rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)" => (1, 30, 0));
+
+        check_parse!("rustc 1.20.0-nightly (d84693b93 2017-07-09)"
+                       => "1.20.0-nightly", Some("2017-07-09"));
+
+        check_parse!("rustc 1.20.0 (d84693b93 2017-07-09)"
+                       => "1.20.0", Some("2017-07-09"));
+
+        check_parse!("warning: invalid logging spec 'warning', ignoring it
+                      rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)"
+                      => "1.30.0-nightly", Some("2018-09-20"));
+
+        check_parse!("warning: invalid logging spec 'warning', ignoring it\n
+                      rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)"
+                      => "1.30.0-nightly", Some("2018-09-20"));
+
+        check_parse!("warning: invalid logging spec 'warning', ignoring it
+                      warning: something else went wrong
+                      rustc 1.30.0-nightly (3bc2ca7e4 2018-09-20)"
+                      => "1.30.0-nightly", Some("2018-09-20"));
     }
 }

src/version.rs

@@ -0,0 +1,221 @@
+use std::fmt;
+
+/// Version number: `major.minor.patch`, ignoring release channel.
+#[derive(Debug, PartialEq, Eq, Copy, Clone, PartialOrd, Ord)]
+pub struct Version(u64);
+
+impl Version {
+    fn to_mmp(&self) -> (u16, u16, u16) {
+        let major = self.0 >> 32;
+        let minor = (self.0 << 32) >> 48;
+        let patch = (self.0 << 48) >> 48;
+        (major as u16, minor as u16, patch as u16)
+    }
+
+    /// Reads the version of the running compiler. If it cannot be determined
+    /// (see the [top-level documentation](crate)), returns `None`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Version;
+    ///
+    /// match Version::read() {
+    ///     Some(d) => format!("Version is: {}", d),
+    ///     None => format!("Failed to read the version.")
+    /// };
+    /// ```
+    pub fn read() -> Option<Version> {
+        ::get_version_and_date()
+            .and_then(|(version, _)| version)
+            .and_then(|version| Version::parse(&version))
+    }
+
+
+    /// Parse a Rust release version (of the form
+    /// `major[.minor[.patch[-channel]]]`), ignoring the release channel, if
+    /// any. Returns `None` if `version` is not a valid Rust version string.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Version;
+    ///
+    /// let version = Version::parse("1.18.0").unwrap();
+    /// assert!(version.exactly("1.18.0"));
+    ///
+    /// let version = Version::parse("1.20.0-nightly").unwrap();
+    /// assert!(version.exactly("1.20.0"));
+    /// assert!(version.exactly("1.20.0-beta"));
+    ///
+    /// let version = Version::parse("1.3").unwrap();
+    /// assert!(version.exactly("1.3.0"));
+    ///
+    /// let version = Version::parse("1").unwrap();
+    /// assert!(version.exactly("1.0.0"));
+    ///
+    /// assert!(Version::parse("one.two.three").is_none());
+    /// ```
+    pub fn parse(version: &str) -> Option<Version> {
+        let mut mmp: Vec<u16> = version.split('-')
+            .nth(0)
+            .unwrap_or("")
+            .split('.')
+            .filter_map(|s| s.parse::<u16>().ok())
+            .collect();
+
+        if mmp.is_empty() {
+            return None
+        }
+
+        while mmp.len() < 3 {
+            mmp.push(0);
+        }
+
+        let (maj, min, patch) = (mmp[0] as u64, mmp[1] as u64, mmp[2] as u64);
+        Some(Version((maj << 32) | (min << 16) | patch))
+    }
+
+    /// Returns `true` if `self` is greater than or equal to `version`.
+    ///
+    /// If `version` is greater than `self`, or if `version` is not a valid Rust
+    /// version string, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Version;
+    ///
+    /// let version = Version::parse("1.35.0").unwrap();
+    ///
+    /// assert!(version.at_least("1.33.0"));
+    /// assert!(version.at_least("1.35.0"));
+    /// assert!(version.at_least("1.13.2"));
+    ///
+    /// assert!(!version.at_least("1.35.1"));
+    /// assert!(!version.at_least("1.55.0"));
+    /// ```
+    pub fn at_least(&self, version: &str) -> bool {
+        Version::parse(version)
+            .map(|version| self >= &version)
+            .unwrap_or(false)
+    }
+
+    /// Returns `true` if `self` is less than or equal to `version`.
+    ///
+    /// If `version` is less than `self`, or if `version` is not a valid Rust
+    /// version string, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Version;
+    ///
+    /// let version = Version::parse("1.35.0").unwrap();
+    ///
+    /// assert!(version.at_most("1.35.1"));
+    /// assert!(version.at_most("1.55.0"));
+    /// assert!(version.at_most("1.35.0"));
+    ///
+    /// assert!(!version.at_most("1.33.0"));
+    /// assert!(!version.at_most("1.13.2"));
+    /// ```
+    pub fn at_most(&self, version: &str) -> bool {
+        Version::parse(version)
+            .map(|version| self <= &version)
+            .unwrap_or(false)
+    }
+
+    /// Returns `true` if `self` is exactly equal to `version`.
+    ///
+    /// If `version` is not equal to `self`, or if `version` is not a valid Rust
+    /// version string, returns `false`.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use version_check::Version;
+    ///
+    /// let version = Version::parse("1.35.0").unwrap();
+    ///
+    /// assert!(version.exactly("1.35.0"));
+    ///
+    /// assert!(!version.exactly("1.33.0"));
+    /// assert!(!version.exactly("1.35.1"));
+    /// assert!(!version.exactly("1.13.2"));
+    /// ```
+    pub fn exactly(&self, version: &str) -> bool {
+        Version::parse(version)
+            .map(|version| self == &version)
+            .unwrap_or(false)
+    }
+}
+
+impl fmt::Display for Version {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let (major, minor, patch) = self.to_mmp();
+        write!(f, "{}.{}.{}", major, minor, patch)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Version;
+
+    macro_rules! check_mmp {
+        ($s:expr => ($x:expr, $y:expr, $z:expr)) => (
+            if let Some(v) = Version::parse($s) {
+                if v.to_mmp() != ($x, $y, $z) {
+                    panic!("{:?} ({}) didn't parse as {}.{}.{}.", $s, v, $x, $y, $z);
+                }
+            } else {
+                panic!("{:?} didn't parse for mmp testing.", $s);
+            }
+        )
+    }
+
+    #[test]
+    fn test_str_to_mmp() {
+        check_mmp!("1.18.0" => (1, 18, 0));
+        check_mmp!("3.19.0" => (3, 19, 0));
+        check_mmp!("1.19.0-nightly" => (1, 19, 0));
+        check_mmp!("1.12.2349" => (1, 12, 2349));
+        check_mmp!("0.12" => (0, 12, 0));
+        check_mmp!("1.12.5" => (1, 12, 5));
+        check_mmp!("1.12" => (1, 12, 0));
+        check_mmp!("1" => (1, 0, 0));
+        check_mmp!("1.4.4-nightly (d84693b93 2017-07-09)" => (1, 4, 4));
+        check_mmp!("1.58879.4478-dev" => (1, 58879, 4478));
+        check_mmp!("1.58879.4478-dev (d84693b93 2017-07-09)" => (1, 58879, 4478));
+    }
+
+    #[test]
+    fn test_comparisons() {
+        let version = Version::parse("1.18.0").unwrap();
+        assert!(version.exactly("1.18.0"));
+        assert!(version.at_least("1.12.0"));
+        assert!(version.at_most("1.18.1"));
+        assert!(!version.exactly("1.19.0"));
+        assert!(!version.exactly("1.18.1"));
+
+        let version = Version::parse("1.20.0-nightly").unwrap();
+        assert!(version.exactly("1.20.0-beta"));
+        assert!(version.exactly("1.20.0-nightly"));
+        assert!(version.exactly("1.20.0"));
+        assert!(!version.exactly("1.19"));
+
+        let version = Version::parse("1.3").unwrap();
+        assert!(version.exactly("1.3.0"));
+        assert!(version.exactly("1.3.0-stable"));
+        assert!(version.exactly("1.3"));
+        assert!(!version.exactly("1.5.0-stable"));
+
+        let version = Version::parse("1").unwrap();
+        assert!(version.exactly("1.0.0"));
+        assert!(version.exactly("1.0"));
+        assert!(version.exactly("1"));
+
+        assert!(Version::parse("one.two.three").is_none());
+    }
+
+}