Fix #1071: Sometimes uses Enumarator instead of Foreach

ICSharpCode.Decompiler.Tests/PrettyTestRunner.cs

@@ -159,7 +159,7 @@ namespace ICSharpCode.Decompiler.Tests
 		}
 
 		[Test]
-		public void Loops([ValueSource("defaultOptions")] CSharpCompilerOptions cscOptions)
+		public void Loops([ValueSource("defaultOptionsWithMcs")] CSharpCompilerOptions cscOptions)
 		{
 			RunForLibrary(cscOptions: cscOptions);
 		}

ICSharpCode.Decompiler.Tests/TestCases/Pretty/Loops.cs

@@ -252,6 +252,9 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 		}
 
+#if MCS
+		[StructLayout(LayoutKind.Sequential, Size = 1)]
+#endif
 		public struct DataItem
 		{
 			public int Property {
@@ -457,12 +460,21 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public void ForEachBreakWhenFound(string name, ref StringComparison output)
 		{
+#if MCS
+			foreach (int value in Enum.GetValues(typeof(StringComparison))) {
+				if (((StringComparison)value).ToString() == name) {
+					output = (StringComparison)value;
+					break;
+				}
+			}
+#else
 			foreach (StringComparison value in Enum.GetValues(typeof(StringComparison))) {
 				if (value.ToString() == name) {
 					output = value;
 					break;
 				}
 			}
+#endif
 		}
 
 		public void ForEachOverListOfStruct(List<DataItem> items, int value)
@@ -496,6 +508,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 		}
 
+#if !MCS
 		public void ForEachOverMultiDimArray(int[,] items)
 		{
 			foreach (int value in items) {
@@ -526,6 +539,8 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			}
 #endif
 		}
+#endif
+
 #endregion
 
 		public void ForOverArray(string[] array)

ICSharpCode.Decompiler/IL/Transforms/UsingTransform.cs

@@ -233,6 +233,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				}
 			} else {
 				ILInstruction target;
+				bool boxedValue = false;
 				if (isReference && checkInst is NullableRewrap rewrap) {
 					// the null check of reference types might have been transformed into "objVar?.Dispose();"
 					if (!(rewrap.Argument is CallVirt cv))
@@ -264,6 +265,10 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					target = cv.Arguments.FirstOrDefault();
 					if (target == null)
 						return false;
+					if (target.MatchBox(out var newTarget, out var type) && type.Equals(objVar.Type)) {
+						boxedValue = type.IsReferenceType != true;
+						target = newTarget;
+					}
 					callVirt = cv;
 				}
 				if (callVirt.Method.FullName != "System.IDisposable.Dispose")
@@ -272,7 +277,7 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					return false;
 				if (callVirt.Arguments.Count != 1)
 					return false;
-				return target.MatchLdLocRef(objVar) || (usingNull && callVirt.Arguments[0].MatchLdNull());
+				return target.MatchLdLocRef(objVar) || (boxedValue && target.MatchLdLoc(objVar)) || (usingNull && callVirt.Arguments[0].MatchLdNull());
 			}
 		}
 	}