the from repr trait

x/src/lib.rs

@@ -25,3 +25,9 @@ import!(sub_xpat, xpat, "xpat");
 pub use sub_macros::{
     FromRepr
 };
+
+#[cfg(feature = "macros")]
+pub trait FromRepr: Sized {
+    type Repr;
+    fn from_repr(repr: Self::Repr) -> Option<Self>;
+}