1 files changed, 84 insertions, 0 deletions
diff --git a/rustversion/src/bound.rs b/rustversion/src/bound.rs
new file mode 100644
index 0000000..2546637
--- /dev/null
+++ b/rustversion/src/bound.rs
@@ -0,0 +1,84 @@
+use crate::date::Date;
+use crate::version::{Channel::*, Version};
+use quote::quote;
+use std::cmp::Ordering;
+use syn::parse::{Error, Parse, ParseStream, Result};
+use syn::{LitFloat, LitInt, Token};
+
+pub enum Bound {
+    Nightly(Date),
+    Stable(Release),
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Release {
+    pub minor: u16,
+    pub patch: Option<u16>,
+}
+
+impl Parse for Bound {
+    fn parse(input: ParseStream) -> Result<Self> {
+        if input.peek2(Token![-]) {
+            input.parse().map(Bound::Nightly)
+        } else {
+            input.parse().map(Bound::Stable)
+        }
+    }
+}
+
+impl Parse for Release {
+    fn parse(input: ParseStream) -> Result<Self> {
+        let span = input.cursor().token_stream();
+        let error = || Error::new_spanned(&span, "expected rustc release number, like 1.31");
+
+        let major_minor: LitFloat = input.parse().map_err(|_| error())?;
+        let string = quote!(#major_minor).to_string();
+
+        if !string.starts_with("1.") {
+            return Err(error());
+        }
+
+        let minor: u16 = string[2..].parse().map_err(|_| error())?;
+
+        let patch = if input.parse::<Option<Token![.]>>()?.is_some() {
+            let int: LitInt = input.parse().map_err(|_| error())?;
+            Some(int.base10_parse().map_err(|_| error())?)
+        } else {
+            None
+        };
+
+        Ok(Release { minor, patch })
+    }
+}
+
+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))
+            }
+        }
+    }
+}