review

compiler/rustc_middle/src/infer/unify_key.rs

@@ -175,19 +175,15 @@ impl<'tcx> UnifyKey for ty::ConstVid<'tcx> {
 impl<'tcx> UnifyValue for ConstVarValue<'tcx> {
     type Error = (&'tcx ty::Const<'tcx>, &'tcx ty::Const<'tcx>);
 
-    fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error> {
-        let (val, origin) = match (value1.val, value2.val) {
+    fn unify_values(&value1: &Self, &value2: &Self) -> Result<Self, Self::Error> {
+        Ok(match (value1.val, value2.val) {
             (ConstVariableValue::Known { .. }, ConstVariableValue::Known { .. }) => {
                 bug!("equating two const variables, both of which have known values")
             }
 
             // If one side is known, prefer that one.
-            (ConstVariableValue::Known { .. }, ConstVariableValue::Unknown { .. }) => {
-                (value1.val, value1.origin)
-            }
-            (ConstVariableValue::Unknown { .. }, ConstVariableValue::Known { .. }) => {
-                (value2.val, value2.origin)
-            }
+            (ConstVariableValue::Known { .. }, ConstVariableValue::Unknown { .. }) => value1,
+            (ConstVariableValue::Unknown { .. }, ConstVariableValue::Known { .. }) => value2,
 
             // If both sides are *unknown*, it hardly matters, does it?
             (
@@ -200,11 +196,12 @@ impl<'tcx> UnifyValue for ConstVarValue<'tcx> {
                 // universe is the minimum of the two universes, because that is
                 // the one which contains the fewest names in scope.
                 let universe = cmp::min(universe1, universe2);
-                (ConstVariableValue::Unknown { universe }, value1.origin)
+                ConstVarValue {
+                    val: ConstVariableValue::Unknown { universe },
+                    origin: value1.origin,
+                }
             }
-        };
-
-        Ok(ConstVarValue { origin, val })
+        })
     }
 }