1 files changed, 124 insertions, 0 deletions
diff --git a/third_party/rust/rustversion/build/rustc.rs b/third_party/rust/rustversion/build/rustc.rs
new file mode 100644
index 0000000000..71a830b93a
--- /dev/null
+++ b/third_party/rust/rustversion/build/rustc.rs
@@ -0,0 +1,124 @@
+use self::Channel::*;
+use std::fmt::{self, Debug};
+
+pub enum ParseResult {
+    Success(Version),
+    OopsClippy,
+    Unrecognized,
+}
+
+#[cfg_attr(test, derive(PartialEq))]
+pub struct Version {
+    pub minor: u16,
+    pub patch: u16,
+    pub channel: Channel,
+}
+
+#[cfg_attr(test, derive(PartialEq))]
+pub enum Channel {
+    Stable,
+    Beta,
+    Nightly(Date),
+    Dev,
+}
+
+#[cfg_attr(test, derive(PartialEq))]
+pub struct Date {
+    pub year: u16,
+    pub month: u8,
+    pub day: u8,
+}
+
+pub fn parse(string: &str) -> ParseResult {
+    let last_line = string.lines().last().unwrap_or(string);
+    let mut words = last_line.trim().split(' ');
+
+    match words.next() {
+        Some("rustc") => {}
+        Some(word) if word.starts_with("clippy") => return ParseResult::OopsClippy,
+        Some(_) | None => return ParseResult::Unrecognized,
+    }
+
+    parse_words(&mut words).map_or(ParseResult::Unrecognized, ParseResult::Success)
+}
+
+fn parse_words(words: &mut dyn Iterator<Item = &str>) -> Option<Version> {
+    let mut version_channel = words.next()?.split('-');
+    let version = version_channel.next()?;
+    let channel = version_channel.next();
+
+    let mut digits = version.split('.');
+    let major = digits.next()?;
+    if major != "1" {
+        return None;
+    }
+    let minor = digits.next()?.parse().ok()?;
+    let patch = digits.next().unwrap_or("0").parse().ok()?;
+
+    let channel = match channel {
+        None => Stable,
+        Some(channel) if channel == "dev" => Dev,
+        Some(channel) if channel.starts_with("beta") => Beta,
+        Some(channel) if channel == "nightly" => match words.next() {
+            Some(hash) if hash.starts_with('(') => match words.next() {
+                None if hash.ends_with(')') => Dev,
+                Some(date) if date.ends_with(')') => {
+                    let mut date = date[..date.len() - 1].split('-');
+                    let year = date.next()?.parse().ok()?;
+                    let month = date.next()?.parse().ok()?;
+                    let day = date.next()?.parse().ok()?;
+                    match date.next() {
+                        None => Nightly(Date { year, month, day }),
+                        Some(_) => return None,
+                    }
+                }
+                None | Some(_) => return None,
+            },
+            Some(_) => return None,
+            None => Dev,
+        },
+        Some(_) => return None,
+    };
+
+    Some(Version {
+        minor,
+        patch,
+        channel,
+    })
+}
+
+impl Debug for Version {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("crate::version::Version")
+            .field("minor", &self.minor)
+            .field("patch", &self.patch)
+            .field("channel", &self.channel)
+            .finish()
+    }
+}
+
+impl Debug for Channel {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            Channel::Stable => formatter.write_str("crate::version::Channel::Stable"),
+            Channel::Beta => formatter.write_str("crate::version::Channel::Beta"),
+            Channel::Nightly(date) => formatter
+                .debug_tuple("crate::version::Channel::Nightly")
+                .field(date)
+                .finish(),
+            Channel::Dev => formatter.write_str("crate::version::Channel::Dev"),
+        }
+    }
+}
+
+impl Debug for Date {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter
+            .debug_struct("crate::date::Date")
+            .field("year", &self.year)
+            .field("month", &self.month)
+            .field("day", &self.day)
+            .finish()
+    }
+}