1 files changed, 63 insertions, 0 deletions
diff --git a/third_party/rust/rustversion/src/bound.rs b/third_party/rust/rustversion/src/bound.rs
new file mode 100644
index 0000000000..a667a5b0dc
--- /dev/null
+++ b/third_party/rust/rustversion/src/bound.rs
@@ -0,0 +1,63 @@
+use crate::date::{self, Date};
+use crate::error::{Error, Result};
+use crate::iter::Iter;
+use crate::release::{self, Release};
+use crate::time;
+use crate::version::{Channel::*, Version};
+use proc_macro::{Group, TokenTree};
+use std::cmp::Ordering;
+
+pub enum Bound {
+    Nightly(Date),
+    Stable(Release),
+}
+
+pub fn parse(paren: Group, iter: Iter) -> Result<Bound> {
+    if let Some(TokenTree::Literal(literal)) = iter.peek() {
+        let repr = literal.to_string();
+        if repr.starts_with(|ch: char| ch.is_ascii_digit()) {
+            if repr.contains('.') {
+                return release::parse(paren, iter).map(Bound::Stable);
+            } else {
+                return date::parse(paren, iter).map(Bound::Nightly);
+            }
+        }
+    }
+    let msg = format!(
+        "expected rustc release number like 1.31, or nightly date like {}",
+        time::today(),
+    );
+    Err(Error::group(paren, msg))
+}
+
+impl PartialEq<Bound> for Version {
+    fn eq(&self, rhs: &Bound) -> bool {
+        match rhs {
+            Bound::Nightly(date) => match self.channel {
+                Stable | Beta | Dev => false,
+                Nightly(nightly) => nightly == *date,
+            },
+            Bound::Stable(release) => {
+                self.minor == release.minor
+                    && release.patch.map_or(true, |patch| self.patch == patch)
+            }
+        }
+    }
+}
+
+impl PartialOrd<Bound> for Version {
+    fn partial_cmp(&self, rhs: &Bound) -> Option<Ordering> {
+        match rhs {
+            Bound::Nightly(date) => match self.channel {
+                Stable | Beta => Some(Ordering::Less),
+                Nightly(nightly) => Some(nightly.cmp(date)),
+                Dev => Some(Ordering::Greater),
+            },
+            Bound::Stable(release) => {
+                let version = (self.minor, self.patch);
+                let bound = (release.minor, release.patch.unwrap_or(0));
+                Some(version.cmp(&bound))
+            }
+        }
+    }
+}