Fix ImmutableHashSet.SetEquals to respect KeyComparer for correctness

Author: aw0lid

src/libraries/System.Collections.Immutable/src/System/Collections/Immutable/ImmutableHashSet_1.cs

@@ -743,25 +743,23 @@ private static bool SetEquals(IEnumerable<T> other, MutationInput origin)
             switch (other)
             {
                 case ImmutableHashSet<T> otherAsImmutableHashSet:
-                    if (otherAsImmutableHashSet.Count != origin.Count)
-                    {
-                        return false;
-                    }
-
                     if (EqualityComparer<IEqualityComparer<T>>.Default.Equals(origin.EqualityComparer, otherAsImmutableHashSet.KeyComparer))
                     {
+                        if (otherAsImmutableHashSet.Count != origin.Count)
+                        {
+                            return false;
+                        }
                         return SetEqualsWithImmutableHashset(otherAsImmutableHashSet, origin);
                     }
                     break;
 
                 case HashSet<T> otherAsHashset:
-                    if (otherAsHashset.Count != origin.Count)
-                    {
-                        return false;
-                    }
-
                     if (EqualityComparer<IEqualityComparer<T>>.Default.Equals(origin.EqualityComparer, otherAsHashset.Comparer))
                     {
+                        if (otherAsHashset.Count != origin.Count)
+                        {
+                            return false;
+                        }
                         return SetEqualsWithHashset(otherAsHashset, origin);
                     }
                     break;