Fix #3385: Allow address uses of structs in using transform, if the reference is passed to an in parameter.

Author: siegfriedpammer

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

@@ -39,6 +39,32 @@ void IDisposable.Dispose()
 			}
 		}
 
+		private struct TypeA_Issue3385 : IDisposable
+		{
+			private int dummy;
+
+			public void Dispose()
+			{
+			}
+
+#if !ROSLYN3
+			public static implicit operator TypeB_Issue3385(TypeA_Issue3385 a)
+			{
+				return default(TypeB_Issue3385);
+			}
+#else
+			public static implicit operator TypeB_Issue3385(in TypeA_Issue3385 a)
+			{
+				return default(TypeB_Issue3385);
+			}
+#endif
+		}
+
+		private struct TypeB_Issue3385
+		{
+			private int dummy;
+		}
+
 #if CS80
 		[StructLayout(LayoutKind.Sequential, Size = 1)]
 		public ref struct UsingRefStruct
@@ -161,5 +187,25 @@ public void UsingRefStruct1(UsingRefStruct s)
 			}
 		}
 #endif
+
+		public static void Issue3385()
+		{
+#if ROSLYN3
+			using (TypeA_Issue3385 a = default(TypeA_Issue3385))
+#else
+			using (TypeA_Issue3385 typeA_Issue = default(TypeA_Issue3385))
+#endif
+			{
+#if ROSLYN3
+				Empty(a);
+#else
+				Empty(typeA_Issue);
+#endif
+			}
+		}
+
+		private static void Empty(TypeB_Issue3385 b)
+		{
+		}
 	}
 }

ICSharpCode.Decompiler/IL/Transforms/ILInlining.cs

@@ -448,7 +448,7 @@ static bool IsUsedAsThisPointerInFieldRead(LdLoca ldloca)
 			return inst != ldloca && inst.Parent is LdObj;
 		}
 
-		static bool IsPassedToInParameter(LdLoca ldloca)
+		internal static bool IsPassedToInParameter(LdLoca ldloca)
 		{
 			if (ldloca.Parent is not CallInstruction call)
 			{

ICSharpCode.Decompiler/IL/Transforms/UsingTransform.cs

@@ -89,7 +89,7 @@ bool TransformUsing(Block block, int i)
 				return false;
 			if (storeInst.Variable.LoadInstructions.Any(ld => !ld.IsDescendantOf(tryFinally)))
 				return false;
-			if (storeInst.Variable.AddressInstructions.Any(la => !la.IsDescendantOf(tryFinally) || (la.IsDescendantOf(tryFinally.TryBlock) && !ILInlining.IsUsedAsThisPointerInCall(la))))
+			if (!storeInst.Variable.AddressInstructions.All(ValidateAddressUse))
 				return false;
 			if (storeInst.Variable.StoreInstructions.Count > 1)
 				return false;
@@ -104,6 +104,18 @@ bool TransformUsing(Block block, int i)
 				IsRefStruct = context.Settings.IntroduceRefModifiersOnStructs && storeInst.Variable.Type.Kind == TypeKind.Struct && storeInst.Variable.Type.IsByRefLike
 			}.WithILRange(storeInst);
 			return true;
+
+			bool ValidateAddressUse(LdLoca la)
+			{
+				if (!la.IsDescendantOf(tryFinally))
+					return false;
+				if (la.IsDescendantOf(tryFinally.TryBlock))
+				{
+					if (!(ILInlining.IsUsedAsThisPointerInCall(la) || ILInlining.IsPassedToInParameter(la)))
+						return false;
+				}
+				return true;
+			}
 		}
 
 		/// <summary>