simplify more

BizHawk.Client.Common/cheats/IDecodeResult.cs

@@ -12,6 +12,7 @@ namespace BizHawk.Client.Common.cheats
 		int? Compare { get; }
 		WatchSize Size { get; }
 		bool IsValid { get; }
+		string Error { get; }
 	}
 
 	public class DecodeResult : IDecodeResult
@@ -21,15 +22,22 @@ namespace BizHawk.Client.Common.cheats
 		public int? Compare { get; internal set; }
 		public WatchSize Size { get; internal set; }
 		public bool IsValid => true;
+		public string Error => "";
 	}
 
 	public class InvalidResult : IDecodeResult
 	{
+		public InvalidResult(string error)
+		{
+			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

BizHawk.Client.Common/cheats/NesGameGenieDecoder.cs

@@ -34,7 +34,7 @@ namespace BizHawk.Client.Common.cheats
 
 			if (code.Length != 6 && code.Length != 8)
 			{
-				return new InvalidResult();
+				return new InvalidResult("Game Genie codes need to be six or eight characters in length.");
 			}
 
 			var result = new DecodeResult { Size = WatchSize.Byte };

BizHawk.Client.EmuHawk/tools/GameShark.cs

@@ -279,11 +279,6 @@ namespace BizHawk.Client.EmuHawk
 
 		private void Nes(string code)
 		{
-			if (code.Length != 6 && code.Length != 8)
-			{
-				InputError("Game Genie codes need to be six or eight characters in length.");
-			}
-
 			var description = Description(code);
 			var result = NesGameGenieDecoder.Decode(code);
 			if (result.IsValid)
@@ -292,7 +287,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 			else
 			{
-				InputError("Invalid Game Genie code");
+				InputError(result.Error);
 			}
 		}