Preserve TypeDelegator and TypeBuilder constant identity

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -1104,10 +1104,15 @@ public static Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>
                 (t1, t2, t3, t4, t5, t6, t7, t8, t9, t10) => f(c, t1, t2, t3, t4, t5, t6, t7, t8, t9, t10);
         }
 
+        // Only the real RuntimeType can be emitted via ldtoken; TypeDelegator/TypeBuilder
+        // must stay in the closure to preserve identity.
+        private static readonly Type RuntimeType = typeof(object).GetType();
+
         /// Helps to identify constants as the one to be put into the Closure
         public static bool IsClosureBoundConstant(object value, Type type) =>
             value is Delegate || type.IsArray ||
-            !type.IsPrimitive && !type.IsEnum && value is string == false && value is Type == false && value is decimal == false;
+            !type.IsPrimitive && !type.IsEnum && value is string == false &&
+            (value is Type == false || type != RuntimeType) && value is decimal == false;
 
         public enum Result
         {

test/FastExpressionCompiler.TestsRunner.Net472/Program.cs

@@ -43,6 +43,7 @@ static void RunLightExpressionTests(object state)
                 t.Run(new LightExpression.IssueTests.Issue476_System_ExecutionEngineException_with_nullables_on_repeated_calls_to_ConcurrentDictionary());
                 t.Run(new LightExpression.IssueTests.Issue498_InvalidProgramException_when_using_loop());
                 t.Run(new LightExpression.IssueTests.Issue499_InvalidProgramException_for_Sorting_and_comparison_function());
+                t.Run(new LightExpression.UnitTests.RuntimeTypeConstantRegressionTests());
                 t.Run(new LightExpression.UnitTests.ParityTests());
 
                 Console.WriteLine($"Just LightExpression tests are passing in {justLightTestsStopwatch.ElapsedMilliseconds} ms.");
@@ -64,6 +65,7 @@ static void RunLightExpressionTests(object state)
             fecTests.Run(new Issue498_InvalidProgramException_when_using_loop());
             fecTests.Run(new Issue499_InvalidProgramException_for_Sorting_and_comparison_function());
             fecTests.Run(new ReductionProgressRegressionTests());
+            fecTests.Run(new RuntimeTypeConstantRegressionTests());
             fecTests.Run(new ParityTests());
 
 

test/FastExpressionCompiler.TestsRunner/Program.cs

@@ -75,6 +75,7 @@ public static void Main(string[] args)
                 lt.Run(new LightExpression.IssueTests.Issue476_System_ExecutionEngineException_with_nullables_on_repeated_calls_to_ConcurrentDictionary());
                 lt.Run(new LightExpression.IssueTests.Issue499_InvalidProgramException_for_Sorting_and_comparison_function());
                 lt.Run(new LightExpression.IssueTests.Issue561_NonBooleanEqualityOperator());
+                lt.Run(new LightExpression.UnitTests.RuntimeTypeConstantRegressionTests());
                 lt.Run(new LightExpression.UnitTests.ParityTests());
                 ltTime = ltStopwatch.ElapsedMilliseconds;
             });
@@ -83,6 +84,7 @@ public static void Main(string[] args)
             st.Run(new Issue499_InvalidProgramException_for_Sorting_and_comparison_function());
             st.Run(new Issue561_NonBooleanEqualityOperator());
             st.Run(new ReductionProgressRegressionTests());
+            st.Run(new RuntimeTypeConstantRegressionTests());
             st.Run(new ParityTests());
             st.Run(new Issue498_InvalidProgramException_when_using_loop());
             st.Run(new Issue495_Incomplete_pattern_detection_for_NotSupported_1007_Return_goto_from_TryCatch_with_Assign_generates_invalid_IL());

test/FastExpressionCompiler.UnitTests/RuntimeTypeConstantRegressionTests.cs

@@ -0,0 +1,34 @@
+using System;
+using System.Reflection;
+using System.Reflection.Emit;
+#if LIGHT_EXPRESSION
+using E = FastExpressionCompiler.LightExpression.Expression;
+namespace FastExpressionCompiler.LightExpression.UnitTests;
+#else
+using E = System.Linq.Expressions.Expression;
+namespace FastExpressionCompiler.UnitTests;
+#endif
+public struct RuntimeTypeConstantRegressionTests : ITestX
+{
+    public void Run(TestRun t) { Nonruntime_type_constants_preserve_identity(t); Runtime_type_constants_keep_token_semantics(t); }
+    public void Nonruntime_type_constants_preserve_identity(TestContext t)
+    {
+        var module = AssemblyBuilder.DefineDynamicAssembly(new AssemblyName("FecTypeConstant"), AssemblyBuilderAccess.Run).DefineDynamicModule("M");
+        foreach (Type value in new Type[] { new TypeDelegator(typeof(int)), module.DefineType("Unfinished") })
+        {
+            var expression = E.Lambda<Func<Type>>(E.Constant(value, typeof(Type)));
+            var fast = expression.CompileFast(true);
+            if (t.IsNotNull(fast)) t.AreEqual(true, ReferenceEquals(value, fast()));
+            var repeated = E.Lambda<Func<bool>>(E.ReferenceEqual(E.Constant(value, typeof(Type)), E.Constant(value, typeof(Type)))).CompileFast(true);
+            if (t.IsNotNull(repeated)) t.AreEqual(true, repeated());
+        }
+    }
+    public void Runtime_type_constants_keep_token_semantics(TestContext t)
+    {
+        foreach (var value in new Type[] { null, typeof(int), typeof(Func<>), typeof(Func<>).GetGenericArguments()[0], typeof(int).MakeByRefType(), typeof(int[,]) })
+        {
+            var fast = E.Lambda<Func<Type>>(E.Constant(value, typeof(Type))).CompileFast(true);
+            if (t.IsNotNull(fast)) t.AreEqual(true, ReferenceEquals(value, fast()));
+        }
+    }
+}