Replace parse return type with ParseResult enum

build/build.rs

@@ -36,8 +36,8 @@ fn main() {
  };
 
  let version = match rustc::parse(&string) {
- Some(version) => version,
- None => {
+ rustc::ParseResult::Success(version) => version,
+ rustc::ParseResult::Unrecognized => {
  eprintln!(
  "Error: unexpected output from `rustc --version`: {:?}\n\n\
  Please file an issue in https://github.com/dtolnay/rustversion",

build/rustc.rs

@@ -1,6 +1,11 @@
 use self::Channel::*;
 use std::fmt::{self, Debug};
 
+pub enum ParseResult {
+ Success(Version),
+ Unrecognized,
+}
+
 #[cfg_attr(test, derive(PartialEq))]
 pub struct Version {
  pub minor: u16,
@@ -23,14 +28,18 @@ pub struct Date {
  pub day: u8,
 }
 
-pub fn parse(string: &str) -> Option<Version> {
+pub fn parse(string: &str) -> ParseResult {
  let last_line = string.lines().last().unwrap_or(string);
  let mut words = last_line.trim().split(' ');
 
- if words.next()? != "rustc" {
- return None;
+ if words.next() != Some("rustc") {
+ 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();

tests/test_parse.rs

@@ -93,6 +93,9 @@ fn test_parse() {
  ];
 
  for (string, expected) in cases {
- assert_eq!(parse(string).unwrap(), *expected);
+ match parse(string) {
+ ParseResult::Success(version) => assert_eq!(version, *expected),
+ ParseResult::Unrecognized => panic!("unrecognized: {:?}", string),
+ }
  }
 }