1 files changed, 193 insertions, 0 deletions
diff --git a/third_party/rust/version_check/src/channel.rs b/third_party/rust/version_check/src/channel.rs
new file mode 100644
index 0000000000..f84c508d16
--- /dev/null
+++ b/third_party/rust/version_check/src/channel.rs
@@ -0,0 +1,193 @@
+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> {
+        let version = version.trim();
+        if version.contains("-dev") || version == "dev" {
+            Some(Channel(Kind::Dev))
+        } else if version.contains("-nightly") || version == "nightly" {
+            Some(Channel(Kind::Nightly))
+        } else if version.contains("-beta") || version == "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())
+    }
+}