Use type checks for DecodeResult/InvalidCheatCode

src/BizHawk.Client.Common/cheats/IDecodeResult.cs

@@ -7,11 +7,6 @@ namespace BizHawk.Client.Common.cheats
 	/// </summary>
 	public interface IDecodeResult
 	{
-		int Address { get; }
-		int Value { get; }
-		int? Compare { get; }
-		WatchSize Size { get; }
-		bool IsValid { get; }
 		string Error { get; }
 	}
 
@@ -21,7 +16,6 @@ namespace BizHawk.Client.Common.cheats
 		public int Value { get; internal set; }
 		public int? Compare { get; internal set; }
 		public WatchSize Size { get; internal set; }
-		public bool IsValid => true;
 		public string Error => "";
 	}
 
@@ -32,17 +26,18 @@ namespace BizHawk.Client.Common.cheats
 			Error = error;
 		}
 
-		public int Address => int.MaxValue;
-		public int Value => int.MaxValue;
-		public int? Compare => null;
-		public WatchSize Size => WatchSize.Separator;
-		public bool IsValid => false;
 		public string Error { get; }
 	}
 
 	public static class DecodeResultExtensions
 	{
-		public static Cheat ToCheat(this IDecodeResult result, MemoryDomain domain, string description)
+		public static bool IsValid(this IDecodeResult result, out DecodeResult valid)
+		{
+			valid = result as DecodeResult;
+			return result is DecodeResult;
+		}
+
+		public static Cheat ToCheat(this DecodeResult result, MemoryDomain domain, string description)
 		{
 			var watch = Watch.GenerateWatch(
 				domain,

src/BizHawk.Client.Common/lua/CommonLibs/ClientLuaLibrary.cs

@@ -334,10 +334,10 @@ namespace BizHawk.Client.Common
 			var decoder = new GameSharkDecoder(MainForm.Emulator.AsMemoryDomains(), MainForm.Emulator.SystemId);
 			var result = decoder.Decode(code);
 			
-			if (result.IsValid)
+			if (result.IsValid(out var valid))
 			{
 				var domain = decoder.CheatDomain();
-				MainForm.CheatList.Add(result.ToCheat(domain, code));
+				MainForm.CheatList.Add(valid.ToCheat(domain, code));
 			}
 			else
 			{
@@ -363,10 +363,10 @@ namespace BizHawk.Client.Common
 			var decoder = new GameSharkDecoder(MainForm.Emulator.AsMemoryDomains(), MainForm.Emulator.SystemId);
 			var result = decoder.Decode(code);
 
-			if (result.IsValid)
+			if (result.IsValid(out var valid))
 			{
 				MainForm.CheatList.RemoveRange(
-					MainForm.CheatList.Where(c => c.Address == result.Address));
+					MainForm.CheatList.Where(c => c.Address == valid.Address));
 			}
 			else
 			{

src/BizHawk.Client.EmuHawk/tools/GameShark.cs

@@ -41,12 +41,12 @@ namespace BizHawk.Client.EmuHawk
 					var result = decoder.Decode(code);
 					var domain = decoder.CheatDomain();
 
-					if (result.IsValid)
+					if (result.IsValid(out var valid))
 					{
 						var description = !string.IsNullOrWhiteSpace(txtDescription.Text)
 							? txtDescription.Text
 							: code;
-						MainForm.CheatList.Add(result.ToCheat(domain, description));
+						MainForm.CheatList.Add(valid.ToCheat(domain, description));
 					}
 					else
 					{