fixed: #308

Author: dadhi

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -3172,12 +3172,12 @@ internal static void EmitLoadConstantsAndNestedLambdasIntoVars(ILGenerator il, r
                 var nestedLambdas = closure.NestedLambdas;
                 for (var i = 0; i < nestedLambdas.Length; i++)
                 {
-                    var nestedLambda = nestedLambdas[i];
                     il.Emit(OpCodes.Ldloc_0);// SHOULD BE always at 0 locaton; load array field variable on the stack
                     EmitLoadConstantInt(il, constCount + i);
                     il.Emit(OpCodes.Ldelem_Ref);
 
                     // store the nested lambda in the local variable 
+                    var nestedLambda = nestedLambdas[i];
                     varIndex = il.GetNextLocalVarIndex(nestedLambda.Lambda.GetType());
                     nestedLambda.LambdaVarIndex = varIndex; // save the var index
                     EmitStoreLocalVariable(il, varIndex);
@@ -4234,11 +4234,20 @@ private static bool TryEmitNestedLambda(LambdaExpression lambdaExpr, IReadOnlyLi
                 // - call `Curry` method with nested lambda and array closure to produce a closed lambda with the expected signature
                 var lambdaTypeArgs = nestedLambda.GetType().GetTypeInfo().GenericTypeArguments;
 
-                var closureMethod = nestedLambdaInfo.LambdaExpression.ReturnType == typeof(void)
+                var nestedLambdaExpr = nestedLambdaInfo.LambdaExpression;
+                var closureMethod = nestedLambdaExpr.ReturnType == typeof(void)
                     ? CurryClosureActions.Methods[lambdaTypeArgs.Length - 1].MakeGenericMethod(lambdaTypeArgs)
                     : CurryClosureFuncs  .Methods[lambdaTypeArgs.Length - 2].MakeGenericMethod(lambdaTypeArgs);
 
                 EmitMethodCall(il, closureMethod);
+
+                // converting to the original possibly custom delegate type, see #308
+                if (closureMethod.ReturnType != nestedLambdaExpr.Type)
+                {
+                    il.Emit(OpCodes.Ldftn, closureMethod.ReturnType.FindDelegateInvokeMethod());
+                    il.Emit(OpCodes.Newobj, nestedLambdaExpr.Type.GetConstructors()[0]);
+                }
+
                 return true;
             }
 
@@ -4663,7 +4672,7 @@ private static bool TryEmitArithmetic(BinaryExpression expr, ExpressionType expr
                         EmitLoadLocalVariable(il, InitValueTypeVariable(il, exprType));
                         il.Emit(OpCodes.Br_S, endL);
                         il.MarkLabel(valueLabel);
-                        il.Emit(OpCodes.Newobj, exprType.GetTypeInfo().DeclaredConstructors.GetFirst());
+                        il.Emit(OpCodes.Newobj, exprType.GetConstructors()[0]);
                         il.MarkLabel(endL);
                     }
                     else

test/FastExpressionCompiler.IssueTests/Issue308_Wrong_delegate_type_returned_with_closure.cs

@@ -19,22 +19,26 @@ public int Run()
 
         delegate string Command();
 
-        //[Test]
+        [Test]
         public void Test1()
         {
             var p = Parameter(typeof(string), "vm");
             var expr = Lambda<Func<string, Command>>(Lambda<Command>(p), p);
 
             expr.PrintCSharp();
 
+            // var x = (Func<string, Issue308_Wrong_delegate_type_returned_with_closure.Command>)((string vm) => //$
+            //     (Issue308_Wrong_delegate_type_returned_with_closure.Command)(() => //$
+            //         vm));
+
             var fSys = expr.CompileSys();
             fSys.PrintIL();
-            
+
             Assert.IsInstanceOf<Command>(fSys(null));
-            
+
             var fFast = expr.CompileFast();
             fFast.PrintIL();
-            
+
             Assert.IsInstanceOf<Command>(fFast(null));
         }
     }

test/FastExpressionCompiler.TestsRunner.Net472/Program.cs

@@ -198,6 +198,9 @@ void Run(Func<int> run, string name = null)
                 Run(new Issue307_Switch_with_fall_through_throws_InvalidProgramException().Run);
                 Run(new FastExpressionCompiler.LightExpression.IssueTests.Issue307_Switch_with_fall_through_throws_InvalidProgramException().Run);
 
+                Run(new Issue308_Wrong_delegate_type_returned_with_closure().Run);
+                Run(new FastExpressionCompiler.LightExpression.IssueTests.Issue308_Wrong_delegate_type_returned_with_closure().Run);
+
                 Console.WriteLine($"============={Environment.NewLine}IssueTests are passing in {sw.ElapsedMilliseconds} ms.");
             });
 

test/FastExpressionCompiler.TestsRunner/Program.cs

@@ -11,7 +11,7 @@ public static void Main()
         {
             RunAllTests();
 
-            //new FastExpressionCompiler.LightExpression.IssueTests.Issue308_Wrong_delegate_type_returned_with_closure().Run();
+            // new FastExpressionCompiler.LightExpression.IssueTests.Issue308_Wrong_delegate_type_returned_with_closure().Run();
 
             // new FastExpressionCompiler.LightExpression.IssueTests.Issue307_Switch_with_fall_through_throws_InvalidProgramException().Run();
             // new FastExpressionCompiler.LightExpression.IssueTests.Issue305_CompileFast_generates_incorrect_code_with_arrays_and_printing().Run();
@@ -219,9 +219,13 @@ void Run(Func<int> run, string name = null)
 
                 Run(new Issue305_CompileFast_generates_incorrect_code_with_arrays_and_printing().Run);
                 Run(new FastExpressionCompiler.LightExpression.IssueTests.Issue305_CompileFast_generates_incorrect_code_with_arrays_and_printing().Run);
+
                 Run(new Issue307_Switch_with_fall_through_throws_InvalidProgramException().Run);
                 Run(new FastExpressionCompiler.LightExpression.IssueTests.Issue307_Switch_with_fall_through_throws_InvalidProgramException().Run);
 
+                Run(new Issue308_Wrong_delegate_type_returned_with_closure().Run);
+                Run(new FastExpressionCompiler.LightExpression.IssueTests.Issue308_Wrong_delegate_type_returned_with_closure().Run);
+
                 Console.WriteLine($"============={Environment.NewLine}IssueTests are passing in {sw.ElapsedMilliseconds} ms.");
             });