Explain why a given pattern is considered unreachable

compiler/rustc_pattern_analysis/src/pat.rs

@@ -11,7 +11,7 @@ use crate::{PatCx, PrivateUninhabitedField};
 use self::Constructor::*;
 
 /// A globally unique id to distinguish patterns.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
 pub(crate) struct PatId(u32);
 impl PatId {
     fn new() -> Self {
@@ -147,6 +147,21 @@ impl<Cx: PatCx> fmt::Debug for DeconstructedPat<Cx> {
     }
 }
 
+/// Delegate to `uid`.
+impl<Cx: PatCx> PartialEq for DeconstructedPat<Cx> {
+    fn eq(&self, other: &Self) -> bool {
+        self.uid == other.uid
+    }
+}
+/// Delegate to `uid`.
+impl<Cx: PatCx> Eq for DeconstructedPat<Cx> {}
+/// Delegate to `uid`.
+impl<Cx: PatCx> std::hash::Hash for DeconstructedPat<Cx> {
+    fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+        self.uid.hash(state);
+    }
+}
+
 /// Represents either a pattern obtained from user input or a wildcard constructed during the
 /// algorithm. Do not use `Wild` to represent a wildcard pattern comping from user input.
 ///