Fix AttributedScopeStack equality type check

src/TextMateSharp.Tests/Internal/Grammars/AttributedScopeStackTests.cs

@@ -0,0 +1,45 @@
+using NUnit.Framework;
+using TextMateSharp.Internal.Grammars;
+
+namespace TextMateSharp.Tests.Internal.Grammars
+{
+    [TestFixture]
+    internal class AttributedScopeStackTests
+    {
+        [Test]
+        public void Equals_ShouldMatchEquivalentStacks()
+        {
+            AttributedScopeStack stack1 = new AttributedScopeStack(new AttributedScopeStack(null, "source.cs", 1), "meta.test", 2);
+            AttributedScopeStack stack2 = new AttributedScopeStack(new AttributedScopeStack(null, "source.cs", 1), "meta.test", 2);
+
+            Assert.IsTrue(stack1.Equals(stack2));
+            Assert.IsTrue(stack2.Equals(stack1));
+        }
+
+        [Test]
+        public void Equals_ShouldReturnFalseForDifferentStacks()
+        {
+            AttributedScopeStack stack1 = new AttributedScopeStack(new AttributedScopeStack(null, "source.cs", 1), "meta.test", 2);
+            AttributedScopeStack stack2 = new AttributedScopeStack(new AttributedScopeStack(null, "source.cs", 1), "meta.other", 2);
+
+            Assert.IsFalse(stack1.Equals(stack2));
+            Assert.IsFalse(stack2.Equals(stack1));
+        }
+
+        [Test]
+        public void Equals_ShouldReturnFalseForDifferentType()
+        {
+            AttributedScopeStack stack = new AttributedScopeStack(null, "source.cs", 1);
+
+            Assert.IsFalse(stack.Equals(42));
+        }
+
+        [Test]
+        public void Equals_ShouldReturnFalseForNull()
+        {
+            AttributedScopeStack stack = new AttributedScopeStack(null, "source.cs", 1);
+
+            Assert.IsFalse(stack.Equals(null));
+        }
+    }
+}

src/TextMateSharp/Internal/Grammars/AttributedScopeStack.cs

@@ -66,7 +66,7 @@ private static bool Equals(AttributedScopeStack a, AttributedScopeStack b)
 
         public override bool Equals(object other)
         {
-            if (other == null || (other is AttributedScopeStack))
+            if (other == null || !(other is AttributedScopeStack))
                 return false;
 
             return Equals(this, (AttributedScopeStack)other);
@@ -206,4 +206,4 @@ private static List<string> GenerateScopes(AttributedScopeStack scopesList)
             return result;
         }
     }
-}
+}