--- /dev/null
+use crate::error::{Error, Result};
+use crate::iter::Iter;
+use crate::token;
+use proc_macro::Group;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Release {
+ pub minor: u16,
+ pub patch: Option<u16>,
+}
+
+pub fn parse(paren: Group, iter: Iter) -> Result<Release> {
+ try_parse(iter).map_err(|_| Error::group(paren, "expected rustc release number, like 1.31"))
+}
+
+fn try_parse(iter: Iter) -> Result<Release, ()> {
+ let major_minor = token::parse_literal(iter).map_err(drop)?;
+ let string = major_minor.to_string();
+
+ if !string.starts_with("1.") {
+ return Err(());
+ }
+
+ let minor: u16 = string[2..].parse().map_err(drop)?;
+
+ let patch = if token::parse_optional_punct(iter, '.').is_some() {
+ let int = token::parse_literal(iter).map_err(drop)?;
+ Some(int.to_string().parse().map_err(drop)?)
+ } else {
+ None
+ };
+
+ Ok(Release { minor, patch })
+}