Fix/equals (#5)

* Showcase the problem

Object equals has a wrong cast

* Correct the type assignment

---------

Co-authored-by: mr.slow <[email protected]>

Author: mitikov

Equativ.RoaringBitmaps.Tests/RoaringBitmapTests.cs

@@ -266,6 +266,25 @@ public void Equal()
         Assert.Equal(rb, rb2);
         Assert.Equal(rb.GetHashCode(), rb2.GetHashCode());
     }
+    
+    [Fact]
+    public void Equals_Simplified()
+    {
+        var rb = RoaringBitmap.Create(1, 2, 3);
+        var rb2 = RoaringBitmap.Create(1, 2, 3);
+
+        Assert.True(rb.Equals(rb2));
+    }
+    
+    /// <summary> Unlike <see cref="Equals_Simplified"/>, uses <see cref="object.Equals(object?)"/> overload. </summary>
+    [Fact]
+    public void ObjectEquals_Simplified()
+    {
+        object rb = RoaringBitmap.Create(1, 2, 3);
+        object rb2 = RoaringBitmap.Create(1, 2, 3);
+
+        Assert.True(rb.Equals(rb2));
+    }
 
     [Fact]
     public void LargeArray()

Equativ.RoaringBitmaps/RoaringBitmap.cs

@@ -53,7 +53,7 @@ public bool Equals(RoaringBitmap? other)
 
     public override bool Equals(object? obj)
     {
-        var ra = obj as RoaringArray;
+        var ra = obj as RoaringBitmap;
         return ra != null && Equals(ra);
     }