Comparison of object to null was crashing due to a bug in enum compar…

…ison template. Fixes issue #17.

Examples/Bugs/X17_IsNull.cs

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2010, Stefan Simek
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ */
+
+// Google Code Issue 17:	Operand.EQ(null) doesn't work
+// Reported by qwertie256, Aug 18, 2010
+
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace TriAxis.RunSharp.Examples.Bugs
+{
+	static class X17_IsNull
+	{
+		public static void GenIsNull(AssemblyGen ag)
+		{
+			TypeGen Test = ag.Class("Test");
+			{
+				CodeGen g = Test.Static.Method(typeof(void), "Main");
+				{
+					Operand a = g.Local(typeof(object), "notnull");
+					Operand b = g.Local(typeof(object), null);
+
+					g.If(a == null);
+					{
+						g.WriteLine("a is null");
+					}
+					g.Else();
+					{
+						g.WriteLine("a is not null");
+					}
+					g.End();
+
+					g.If(b == null);
+					{
+						g.WriteLine("b is null");
+					}
+					g.Else();
+					{
+						g.WriteLine("b is not null");
+					}
+					g.End();
+				}
+			}
+		}
+	}
+}

Examples/Examples.csproj

@@ -51,6 +51,7 @@
     <Compile Include="A2_Attributes.cs">
       <SubType>Code</SubType>
     </Compile>
+    <Compile Include="Bugs\X17_IsNull.cs" />
     <Compile Include="Bugs\X14_StaticConstructor.cs" />
     <Compile Include="Program.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />

RunSharp/Operator.cs

@@ -317,6 +317,9 @@ private CmpOp()
 
 		static IMemberInfo[] CmpEnumSpecific(Operand[] args)
 		{
+			if ((object)args[0] == null || (object)args[1] == null)	// if any of the operands is null, it can't be an enum
+				return stdNone;
+
 			Type t1 = args[0].Type, t2 = args[1].Type;
 
 			if (t1 != t2 || t1 == null || !t1.IsEnum)	// if both types are not the same enum, no operator can be valid