Add Analyzer rules to prohibit `this.GetType()`

seriously Meziantou is a godsend

Common.ruleset

@@ -16,6 +16,12 @@
 		<!-- Default branch of switch expression should throw InvalidOperationException/SwitchExpressionException or not throw -->
 		<Rule Id="BHI1005" Action="Error" />
 
+		<!-- Don't call this.GetType() in sealed type, use typeof operator -->
+		<Rule Id="BHI1100" Action="Error" />
+
+		<!-- Don't call this.GetType(), use typeof operator (or replace subtype check with better encapsulation) -->
+		<Rule Id="BHI1101" Action="Error" />
+
 		<!-- Throw NotImplementedException from methods/props marked [FeatureNotImplemented] -->
 		<Rule Id="BHI3300" Action="Error" />
 	</Rules>

ExternalProjects/BizHawk.Analyzer/RoslynUtils.cs

@@ -1,10 +1,18 @@
 namespace BizHawk.Analyzers;
 
 using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 
 internal static class RoslynUtils
 {
+	public static SyntaxNode? EnclosingTypeDeclarationSyntax(this CSharpSyntaxNode node)
+	{
+		var parent = node.Parent;
+		while (parent is not (null or TypeDeclarationSyntax)) parent = parent.Parent;
+		return parent;
+	}
+
 	private static ITypeSymbol? GetThrownExceptionType(this SemanticModel model, ExpressionSyntax exprSyn)
 		=> exprSyn is ObjectCreationExpressionSyntax
 			? model.GetTypeInfo(exprSyn).Type
@@ -16,6 +24,6 @@ internal static class RoslynUtils
 	public static ITypeSymbol? GetThrownExceptionType(this SemanticModel model, ThrowStatementSyntax tss)
 		=> model.GetThrownExceptionType(tss.Expression!);
 
-	public static bool Matches(this ITypeSymbol expected, ITypeSymbol? actual)
+	public static bool Matches(this ISymbol expected, ISymbol? actual)
 		=> SymbolEqualityComparer.Default.Equals(expected, actual);
 }

ExternalProjects/BizHawk.Analyzer/UseTypeofOperatorAnalyzer.cs

@@ -0,0 +1,50 @@
+namespace BizHawk.Analyzers;
+
+using System.Collections.Immutable;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Operations;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class UseTypeofOperatorAnalyzer : DiagnosticAnalyzer
+{
+	private static readonly DiagnosticDescriptor DiagNoGetTypeOnThis = new(
+		id: "BHI1101",
+		title: "Don't call this.GetType(), use typeof operator (or replace subtype check with better encapsulation)",
+		messageFormat: "Replace this.GetType() with typeof({0}) (or replace subtype check with better encapsulation)",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Warning,
+		isEnabledByDefault: true);
+
+	private static readonly DiagnosticDescriptor DiagNoGetTypeOnThisSealed = new(
+		id: "BHI1100",
+		title: "Don't call this.GetType() in sealed type, use typeof operator",
+		messageFormat: "Replace this.GetType() with typeof({0})",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Error,
+		isEnabledByDefault: true);
+
+	public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(DiagNoGetTypeOnThisSealed, DiagNoGetTypeOnThis);
+
+	public override void Initialize(AnalysisContext context)
+	{
+		context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+		context.EnableConcurrentExecution();
+		ISymbol? objectDotGetTypeSym = null;
+		context.RegisterOperationAction(
+			oac =>
+			{
+				var operation = (IInvocationOperation) oac.Operation;
+				if (operation.IsImplicit || operation.Instance is null) return;
+				objectDotGetTypeSym ??= oac.Compilation.GetTypeByMetadataName("System.Object")!.GetMembers("GetType")[0];
+				if (!objectDotGetTypeSym.Matches(operation.TargetMethod)) return;
+				if (operation.Instance.Syntax is not ThisExpressionSyntax and not IdentifierNameSyntax { Identifier.Text: "GetType" }) return; // called on something that isn't `this`
+				var enclosingType = operation.SemanticModel.GetDeclaredSymbol(((CSharpSyntaxNode) operation.Syntax).EnclosingTypeDeclarationSyntax()!)!;
+				oac.ReportDiagnostic(Diagnostic.Create(enclosingType.IsSealed ? DiagNoGetTypeOnThisSealed : DiagNoGetTypeOnThis, operation.Syntax.GetLocation(), enclosingType.Name));
+			},
+			OperationKind.Invocation);
+	}
+}

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Datacorder/DatacorderDevice.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// <summary>
 	/// Represents the tape device
 	/// </summary>
-	public class DatacorderDevice
+	public sealed class DatacorderDevice
 	{
 		private CPCBase _machine;
 		private Z80A _cpu => _machine.CPU;
@@ -348,7 +348,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nTape image file has a valid CDT header, but threw an exception whilst data was being parsed.\n\n" + e.ToString());
 				}
 			}

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Hardware/Disk/NECUPD765.FDD.cs

@@ -170,7 +170,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// <summary>
 		/// Holds specfic state information about a drive
 		/// </summary>
-		private class DriveState : IFDDHost
+		private sealed class DriveState : IFDDHost
 		{
 			/// <summary>
 			/// The drive ID from an FDC perspective
@@ -775,7 +775,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 
 				if (!found)
 				{
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DriveState).ToString() +
 						"\n\nDisk image file could not be parsed. Potentially an unknown format.");
 				}
 			}

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Machine/CPCBase.Media.cs

@@ -214,7 +214,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// </summary>
 		protected void LoadDiskMedia()
 		{
-			if (this.GetType() == typeof(CPC464))
+			if (this is CPC464)
 			{
 				CPC.CoreComm.ShowMessage("You are trying to load one of more disk images.\n\n Please select something other than CPC 464 emulation immediately and reboot the core");
 				return;

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Media/MediaConverter.cs

@@ -24,12 +24,14 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// </summary>
 		public virtual bool IsWriter => false;
 
+		protected abstract Type SelfType { get; }
+
 		/// <summary>
 		/// Serialization method
 		/// </summary>
 		public virtual void Read(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType() +
+			throw new NotImplementedException(SelfType +
 				"Read operation is not implemented for this converter");
 		}
 
@@ -38,7 +40,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// </summary>
 		public virtual void Write(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType() +
+			throw new NotImplementedException(SelfType +
 				"Write operation is not implemented for this converter");
 		}
 
@@ -47,7 +49,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// </summary>
 		public virtual bool CheckType(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType().ToString() +
+			throw new NotImplementedException(SelfType.ToString() +
 				"Check type operation is not implemented for this converter");
 		}
 

src/BizHawk.Emulation.Cores/Computers/AmstradCPC/Media/Tape/CDT/CdtConverter.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 	/// <summary>
 	/// Responsible for TZX format serialization
 	/// </summary>
-	public class CdtConverter : MediaConverter
+	public sealed class CdtConverter : MediaConverter
 	{
 		/// <summary>
 		/// The type of serializer
@@ -26,6 +26,9 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(CdtConverter);
+
 		/// <summary>
 		/// Working list of generated tape data blocks
 		/// </summary>
@@ -164,7 +167,7 @@ namespace BizHawk.Emulation.Cores.Computers.AmstradCPC
 			if (ident != "ZXTape!" || eotm != 0x1A)
 			{
 				// this is not a valid TZX format file
-				throw new Exception(this.GetType() +
+				throw new Exception(typeof(CdtConverter) +
 					"This is not a valid TZX format file");
 			}
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Datacorder/DatacorderDevice.cs

@@ -11,7 +11,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// <summary>
 	/// Represents the tape device (or build-in datacorder as it was called +2 and above)
 	/// </summary>
-	public class DatacorderDevice : IPortIODevice
+	public sealed class DatacorderDevice : IPortIODevice
 	{
 		private SpectrumBase _machine { get; set; }
 		private Z80A _cpu { get; set; }
@@ -312,7 +312,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nTape image file has a valid TZX header, but threw an exception whilst data was being parsed.\n\n" + e.ToString());
 				}
 			}
@@ -332,7 +332,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nTape image file has a valid PZX header, but threw an exception whilst data was being parsed.\n\n" + e.ToString());
 				}
 			}
@@ -352,7 +352,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nTape image file has a valid CSW header, but threw an exception whilst data was being parsed.\n\n" + e.ToString());
 				}
 			}
@@ -372,7 +372,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nTape image file has a valid WAV header, but threw an exception whilst data was being parsed.\n\n" + e.ToString());
 				}
 			}
@@ -391,7 +391,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				{
 					// exception during operation
 					var e = ex;
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DatacorderDevice).ToString() +
 					"\n\nAn exception was thrown whilst data from this tape image was being parsed as TAP.\n\n" + e.ToString());
 				}
 			}

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Hardware/Disk/NECUPD765.FDD.cs

@@ -170,7 +170,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// <summary>
 		/// Holds specfic state information about a drive
 		/// </summary>
-		private class DriveState : IFDDHost
+		private sealed class DriveState : IFDDHost
 		{
 			/// <summary>
 			/// The drive ID from an FDC perspective
@@ -776,7 +776,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 
 				if (!found)
 				{
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(DriveState).ToString() +
 						"\n\nDisk image file could not be parsed. Potentially an unknown format.");
 				}
 			}

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.Media.cs

@@ -227,7 +227,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// </summary>
         protected void LoadDiskMedia()
         {
-            if (this.GetType() != typeof(ZX128Plus3))
+            if (this is not ZX128Plus3)
             {
                 Spectrum.CoreComm.ShowMessage("You are trying to load one of more disk images.\n\n Please select ZX Spectrum +3 emulation immediately and reboot the core");
                 return;

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/SpectrumBase.Memory.cs

@@ -157,16 +157,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
         /// Detects whether this is a 48k machine (or a 128k in 48k mode)
         /// </summary>
         public virtual bool IsIn48kMode()
-        {
-            if (this.GetType() == typeof(ZX48) ||
-                this.GetType() == typeof(ZX16) ||
-                PagingDisabled)
-            {
-                return true;
-            }
-            else
-                return false;
-        }
+            => PagingDisabled || this is ZX48 or ZX16;
 
         /// <summary>
         /// Monitors ROM access

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/MediaConverter.cs

@@ -26,12 +26,14 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public virtual bool IsWriter => false;
 
+		protected abstract Type SelfType { get; }
+
 		/// <summary>
 		/// Serialization method
 		/// </summary>
 		public virtual void Read(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType().ToString() +
+			throw new NotImplementedException(SelfType.ToString() +
 				"Read operation is not implemented for this converter");
 		}
 
@@ -40,7 +42,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public virtual void Write(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType().ToString() +
+			throw new NotImplementedException(SelfType.ToString() +
 				"Write operation is not implemented for this converter");
 		}
 
@@ -49,7 +51,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public virtual bool CheckType(byte[] data)
 		{
-			throw new NotImplementedException(this.GetType().ToString() +
+			throw new NotImplementedException(SelfType.ToString() +
 				"Check type operation is not implemented for this converter");
 		}
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/CSW/CswConverter.cs

@@ -9,7 +9,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// Responsible for Compressed Square Wave conversion
 	/// https://web.archive.org/web/20171024182530/http://ramsoft.bbk.org.omegahg.com/csw.html
 	/// </summary>
-	public class CswConverter : MediaConverter
+	public sealed class CswConverter : MediaConverter
 	{
 		/// <summary>
 		/// The type of serializer
@@ -32,6 +32,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(CswConverter);
+
 		private readonly DatacorderDevice _datacorder;
 
 		public CswConverter(DatacorderDevice _tapeDevice)
@@ -80,14 +83,14 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			if (ident.ToUpper() != "COMPRESSED SQUARE WAVE")
 			{
 				// this is not a valid CSW format file
-				throw new Exception(this.GetType().ToString() +
+				throw new Exception(typeof(CswConverter).ToString() +
 					"This is not a valid CSW format file");
 			}
 
 			if (data[0x16] != 0x1a)
 			{
 				// invalid terminator code
-				throw new Exception(this.GetType().ToString() +
+				throw new Exception(typeof(CswConverter).ToString() +
 					"This image reports as a CSW but has an invalid terminator code");
 			}
 
@@ -182,12 +185,12 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 				if (compressionType == 1)
 					Array.Copy(data, _position, cswDataUncompressed, 0, cswDataUncompressed.Length);
 				else
-					throw new Exception(this.GetType().ToString() +
+					throw new Exception(typeof(CswConverter).ToString() +
 					"CSW Format unknown compression type");
 			}
 			else
 			{
-				throw new Exception(this.GetType().ToString() +
+				throw new Exception(typeof(CswConverter).ToString() +
 					"CSW Format Version " + majorVer + "." + minorVer + " is not currently supported");
 			}
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/PZX/PzxConverter.cs

@@ -9,7 +9,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// Reponsible for PZX format serializaton
 	/// Based on the information here:  http://zxds.raxoft.cz/docs/pzx.txt
 	/// </summary>
-	public class PzxConverter : MediaConverter
+	public sealed class PzxConverter : MediaConverter
 	{
 		/// <summary>
 		/// The type of serializer
@@ -27,6 +27,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(PzxConverter);
+
 		/// <summary>
 		/// Working list of generated tape data blocks
 		/// </summary>
@@ -96,7 +99,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			if (ident.ToUpper() != "PZXT")
 			{
 				// this is not a valid TZX format file
-				throw new Exception(this.GetType().ToString() +
+				throw new Exception(typeof(PzxConverter).ToString() +
 					"This is not a valid PZX format file");
 			}
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/TAP/TapConverter.cs

@@ -27,6 +27,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(TapConverter);
+
 		private readonly DatacorderDevice _datacorder;
 
 		public TapConverter(DatacorderDevice _tapeDevice)

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/TZX/TzxConverter.cs

@@ -8,7 +8,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// <summary>
 	/// Reponsible for TZX format serializaton
 	/// </summary>
-	public class TzxConverter : MediaConverter
+	public sealed class TzxConverter : MediaConverter
 	{
 		/// <summary>
 		/// The type of serializer
@@ -26,6 +26,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(TzxConverter);
+
 		/// <summary>
 		/// Working list of generated tape data blocks
 		/// </summary>
@@ -202,7 +205,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			if (ident != "ZXTape!" || eotm != 0x1A)
 			{
 				// this is not a valid TZX format file
-				throw new Exception(this.GetType() +
+				throw new Exception(typeof(TzxConverter) +
 					"This is not a valid TZX format file");
 			}
 

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Media/Tape/WAV/WavConverter.cs

@@ -10,7 +10,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 	/// Reponsible for WAV format conversion
 	/// Based heavily on code from zxmak2: https://archive.codeplex.com/?p=zxmak2
 	/// </summary>
-	public class WavConverter : MediaConverter
+	public sealed class WavConverter : MediaConverter
 	{
 		/// <summary>
 		/// The type of serializer
@@ -28,6 +28,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 		/// </summary>
 		public override bool IsWriter => false;
 
+		protected override Type SelfType
+			=> typeof(WavConverter);
+
 		/// <summary>
 		/// Position counter
 		/// </summary>
@@ -74,7 +77,7 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
 			if (ident.ToUpper() != "WAVE")
 			{
 				// this is not a valid TZX format file
-				throw new Exception(this.GetType().ToString() +
+				throw new Exception(typeof(WavConverter).ToString() +
 					"This is not a valid WAV format file");
 			}
 

src/BizHawk.Emulation.Cores/Consoles/Nintendo/BSNES/BsnesApi.cs

@@ -212,7 +212,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 		}
 
 		[StructLayout(LayoutKind.Sequential)]
-		public class SnesCallbacks
+		public sealed class SnesCallbacks
 		{
 			public snes_video_frame_t videoFrameCb;
 			public snes_audio_sample_t audioSampleCb;
@@ -233,7 +233,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.BSNES
 
 			public IEnumerable<Delegate> AllDelegatesInMemoryOrder()
 			{
-				FieldsInOrder ??= GetType()
+				FieldsInOrder ??= typeof(SnesCallbacks)
 					.GetFields()
 					.OrderBy(BizInvokerUtilities.ComputeFieldOffset)
 					.ToList();

src/BizHawk.Emulation.Cores/Consoles/Nintendo/QuickNES/QuickNES.cs

@@ -15,8 +15,9 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.QuickNES
 {
 	[PortedCore(CoreNames.QuickNes, "", "0.7.0", "https://github.com/kode54/QuickNES")]
 	[ServiceNotApplicable(new[] { typeof(IDriveLight) })]
-	public partial class QuickNES : IEmulator, IVideoProvider, ISoundProvider, ISaveRam, IInputPollable, IBoardInfo, IVideoLogicalOffsets,
-		IStatable, IDebuggable, ISettable<QuickNES.QuickNESSettings, QuickNES.QuickNESSyncSettings>, INESPPUViewable
+	public sealed partial class QuickNES : IEmulator, IVideoProvider, ISoundProvider, ISaveRam, IInputPollable,
+		IBoardInfo, IVideoLogicalOffsets, IStatable, IDebuggable,
+		ISettable<QuickNES.QuickNESSettings, QuickNES.QuickNESSyncSettings>, INESPPUViewable
 	{
 		static QuickNES()
 		{
@@ -292,7 +293,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Nintendo.QuickNES
 		private void CheckDisposed()
 		{
 			if (Context == IntPtr.Zero)
-				throw new ObjectDisposedException(GetType().Name);
+				throw new ObjectDisposedException(typeof(QuickNES).Name);
 		}
 
 		// Fix some incorrect ines header entries that QuickNES uses to load games.

src/BizHawk.Emulation.Cores/Consoles/Sega/gpgx64/GenDbgHlp.cs

@@ -23,7 +23,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 	 * 3) support an ignore list of symbols
 	 */
 
-	public class GenDbgHlp : IDisposable
+	public sealed class GenDbgHlp : IDisposable
 	{
 		// config
 		private const string modulename = "libgenplusgx.dll";
@@ -49,7 +49,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 
 		public void SaveState(int statenum)
 		{
-			if (disposed) throw new ObjectDisposedException(this.GetType().ToString());
+			if (disposed) throw new ObjectDisposedException(typeof(GenDbgHlp).ToString());
 
 			data[statenum] ??= new byte[length];
 
@@ -60,7 +60,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 
 		public unsafe void Cmp(int statex, int statey)
 		{
-			if (disposed) throw new ObjectDisposedException(this.GetType().ToString());
+			if (disposed) throw new ObjectDisposedException(typeof(GenDbgHlp).ToString());
 			List<Tuple<int, int>> bads = new List<Tuple<int, int>>();
 
 			byte[] x = data[statex];
@@ -134,7 +134,7 @@ namespace BizHawk.Emulation.Cores.Consoles.Sega.gpgx
 
 		public List<Symbol> Find(IntPtr addr, int length)
 		{
-			if (disposed) throw new ObjectDisposedException(this.GetType().ToString());
+			if (disposed) throw new ObjectDisposedException(typeof(GenDbgHlp).ToString());
 			Symbol min = new Symbol { addr = addr };
 			Symbol max = new Symbol { addr = addr + length };