Fix false positive in struct initializers with default.value init

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

@@ -338,7 +338,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			InitializerTests.X(InitializerTests.Y(), new Data {
 				MoreData = {
 					a = MyEnum.a,
-					[2] = (Data)null
+					[2] = null
 				}
 			});
 		}
@@ -348,11 +348,13 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 			InitializerTests.X(InitializerTests.Y(), new Data {
 				MoreData = {
 					a = MyEnum.a,
-					[GetInt()] = {
+					[InitializerTests.GetInt()] = {
 						a = MyEnum.b,
-						FieldList = { MyEnum2.c },
+						FieldList = {
-						[GetInt(), GetString()] = new Data(),
+							MyEnum2.c
-						[2] = (Data)null
+						},
+						[InitializerTests.GetInt(), InitializerTests.GetString()] = new Data(),
+						[2] = null
 					}
 				}
 			});
@@ -397,7 +399,7 @@ namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
 
 		public static void NotAStructInitializer_DefaultConstructor()
 		{
-			StructData structData = new StructData();
+			StructData structData = default(StructData);
 			structData.Field = 1;
 			structData.Property = 2;
 			InitializerTests.X(InitializerTests.Y(), structData);

ICSharpCode.Decompiler/IL/Transforms/TransformCollectionAndObjectInitializers.cs

@@ -66,6 +66,13 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 						instType = newObjInst.Method.DeclaringType;
 						break;
 					case DefaultValue defaultVal:
+						if (defaultVal.ILStackWasEmpty && v.Kind == VariableKind.Local && !context.Function.Method.IsConstructor) {
+							// on statement level (no other expressions on IL stack),
+							// prefer to keep local variables (but not stack slots),
+							// unless we are in a constructor (where inlining object initializers might be critical
+							// for the base ctor call)
+							return false;
+						}
 						instType = defaultVal.Type;
 						break;
 					case Block existingInitializer: