yet another fix for the #305

Author: dadhi

src/FastExpressionCompiler/FastExpressionCompiler.cs

@@ -3339,6 +3339,15 @@ private static bool TryEmitArrayIndex(Type type, ILGenerator il, ParentFlags par
                     il.Emit(OpCodes.Ldelem_Ref);
                     return true;
                 }
+
+                // access the value type by address when it is used later for the member access or as instance in the method call
+                if ((parent & (ParentFlags.MemberAccess | ParentFlags.InstanceAccess)) != 0)
+                {
+                    il.Emit(OpCodes.Ldelema, type);
+                    closure.LastEmitIsAddress = true;
+                    return true;
+                }
+
                 if (type == typeof(Int32))
                     il.Emit(OpCodes.Ldelem_I4);
                 else if (type == typeof(Int64))
@@ -3361,13 +3370,8 @@ private static bool TryEmitArrayIndex(Type type, ILGenerator il, ParentFlags par
                     il.Emit(OpCodes.Ldelem_U2);
                 else if (type == typeof(UInt32))
                     il.Emit(OpCodes.Ldelem_U4);
-                else if ((parent & (ParentFlags.MemberAccess | ParentFlags.InstanceAccess)) == 0)
-                    il.Emit(OpCodes.Ldelem, type);
                 else
-                {
-                    il.Emit(OpCodes.Ldelema, type);
-                    closure.LastEmitIsAddress = true;
-                }
+                    il.Emit(OpCodes.Ldelem, type);
                 return true;
             }
 
@@ -3966,7 +3970,6 @@ private static bool TryEmitIndexAssign(IndexExpression indexExpr, Type instType,
                         il.Emit(OpCodes.Stelem_I);
                     else
                         il.Emit(OpCodes.Stelem, elementType);
-                        //todo: UInt64 as there is no OpCodes? Stelem_Ref?
                     return true;
                 }
 

test/FastExpressionCompiler.IssueTests/Issue305_CompileFast_generates_incorrect_code_with_arrays_and_printing.cs

@@ -17,16 +17,18 @@ public class Issue305_CompileFast_generates_incorrect_code_with_arrays_and_print
     {
         public int Run()
         {
-            Test1();
-            return 1;
+            Test_double_array_index_access();
+            Test_double_array_index_access_and_instance_call();
+            return 2;
         }
 
         private List<double> _items = new List<double>();
 
         public void WriteLine(double n) => _items.Add(n);
+        public void WriteLine(int n) => _items.Add(n);
 
         [Test]
-        public void Test1()
+        public void Test_double_array_index_access()
         {
             var arr = Variable(typeof(double[]), "arr");
 
@@ -60,5 +62,42 @@ public void Test1()
             Assert.AreEqual(123.456, res2);
             Assert.AreEqual(4, _items.Count(x => x == 123.456));
         }
+
+        [Test]
+        public void Test_double_array_index_access_and_instance_call()
+        {
+            var arr = Variable(typeof(double[]), "arr");
+
+            var print = this.GetType().GetMethod(nameof(WriteLine), new[] { typeof(int) });
+            var compareTo = typeof(double).GetMethod(nameof(double.CompareTo), new[] { typeof(double) });
+
+            var expr = Lambda<Func<double>>(
+                Block(new[] { arr },
+                    Assign(arr, NewArrayBounds(typeof(double), Constant(1))),
+                    Assign(ArrayAccess(arr, Constant(0)), Constant(123.456)),
+
+                    Call(Constant(this), print, Call(ArrayAccess(arr, Constant(0)), compareTo, Constant(123.456))),
+                    Call(Constant(this), print, Call(ArrayAccess(arr, Constant(0)), compareTo, Constant(123.456))),
+
+                    ArrayAccess(arr, Constant(0))
+            ));
+
+            expr.PrintCSharp();
+
+            _items.Clear();
+
+            var fs = expr.CompileSys();
+            fs.PrintIL();
+
+            var res = fs();
+            Assert.AreEqual(123.456, res);
+
+            var ff = expr.CompileFast(true);
+            ff.PrintIL();
+
+            var res2 = ff();
+            Assert.AreEqual(123.456, res2);
+            Assert.AreEqual(4, _items.Count(x => x == 0));
+        }
     }
 }