1 files changed, 62 insertions, 0 deletions
diff --git a/third_party/rust/matches/lib.rs b/third_party/rust/matches/lib.rs
new file mode 100644
index 000000000..eeba978cf
--- /dev/null
+++ b/third_party/rust/matches/lib.rs
@@ -0,0 +1,62 @@
+#[macro_export]
+macro_rules! matches {
+    ($expression:expr, $($pattern:tt)+) => {
+        _matches_tt_as_expr_hack! {
+            match $expression {
+                $($pattern)+ => true,
+                _ => false
+            }
+        }
+    }
+}
+
+/// Work around "error: unexpected token: `an interpolated tt`", whatever that means.
+#[macro_export]
+macro_rules! _matches_tt_as_expr_hack {
+    ($value:expr) => ($value)
+}
+
+#[macro_export]
+macro_rules! assert_matches {
+    ($expression:expr, $($pattern:tt)+) => {
+        _matches_tt_as_expr_hack! {
+            match $expression {
+                $($pattern)+ => (),
+                ref e => panic!("assertion failed: `{:?}` does not match `{}`", e, stringify!($($pattern)+)),
+            }
+        }
+    }
+}
+
+#[macro_export]
+macro_rules! debug_assert_matches {
+    ($($arg:tt)*) => (if cfg!(debug_assertions) { assert_matches!($($arg)*); })
+}
+
+#[test]
+fn matches_works() {
+    let foo = Some("-12");
+    assert!(matches!(foo, Some(bar) if
+        matches!(bar.as_bytes()[0], b'+' | b'-') &&
+        matches!(bar.as_bytes()[1], b'0'...b'9')
+    ));
+}
+
+#[test]
+fn assert_matches_works() {
+    let foo = Some("-12");
+    assert_matches!(foo, Some(bar) if
+        matches!(bar.as_bytes()[0], b'+' | b'-') &&
+        matches!(bar.as_bytes()[1], b'0'...b'9')
+    );
+}
+
+#[test]
+#[should_panic(expected = "assertion failed: `Some(\"-AB\")` does not match ")]
+fn assert_matches_panics() {
+    let foo = Some("-AB");
+    assert_matches!(foo, Some(bar) if
+        matches!(bar.as_bytes()[0], b'+' | b'-') &&
+        matches!(bar.as_bytes()[1], b'0'...b'9')
+    );
+}