Misc. refactors, reverting some code style "fixes"

src/BizHawk.Client.EmuHawk/AVOut/SynclessRecordingTools.cs

@@ -6,6 +6,7 @@ using System.Windows.Forms;
 
 using BizHawk.Bizware.Graphics;
 using BizHawk.Client.Common;
+using BizHawk.Common.StringExtensions;
 using BizHawk.Emulation.Common;
 
 namespace BizHawk.Client.EmuHawk
@@ -50,13 +51,9 @@ namespace BizHawk.Client.EmuHawk
 			string framesDir = "";
 			foreach (var line in lines)
 			{
-				int idx = line.IndexOf('=');
+				const string KEY = "framesdir=";
-				string key = line[..idx];
+				if (line.StartsWithOrdinal(KEY)) framesDir = line.Substring(startIndex: KEY.Length);
-				string value = line[(idx + 1)..];
+				// and continue
-				if (key == "framesdir")
-				{
-					framesDir = value;
-				}
 			}
 
 			_mFramesDirectory = Path.Combine(Path.GetDirectoryName(Path.GetFullPath(_mSynclessConfigFile)), framesDir);

src/BizHawk.Client.EmuHawk/ArchiveChooser.cs

@@ -136,7 +136,7 @@ namespace BizHawk.Client.EmuHawk
 			catch (ArgumentException ex)
 			{
 				string errMsg = ex.Message;
-				errMsg = errMsg[(errMsg.IndexOf('-') + 2)..];
+				errMsg = errMsg.Substring(startIndex: errMsg.IndexOf('-') + 2);
 
 				// Balloon is bugged on first invocation
 				_errorBalloon.Show($"Error parsing RegEx: {errMsg}", tb);

src/BizHawk.Client.EmuHawk/Input/Input.cs

@@ -27,7 +27,9 @@ namespace BizHawk.Client.EmuHawk
 
 		private readonly HashSet<Control> _wantingMouseFocus = new HashSet<Control>();
 
-		public static Input Instance { get; set; }
+#pragma warning disable CA2211 // public field
+		public static Input Instance;
+#pragma warning restore CA2211
 
 		private readonly Thread _updateThread;
 

src/BizHawk.Client.EmuHawk/RetroAchievements/RetroAchievements.GameVerification.cs

@@ -124,7 +124,7 @@ namespace BizHawk.Client.EmuHawk
 							// end of the path has ;
 							var end = exePath.IndexOf(';');
 							if (end < 0) break;
-							exePath = exePath[index..end];
+							exePath = exePath.Substring(startIndex: index, length: end - index);
 						}
 
 						buffer.AddRange(Encoding.ASCII.GetBytes(exePath));

src/BizHawk.Client.EmuHawk/config/FirmwaresConfig.cs

@@ -184,7 +184,7 @@ namespace BizHawk.Client.EmuHawk
 				lvFirmwares.Groups.Add(
 					key: sysID,
 					headerText: SystemGroupNames.TryGetValue(sysID, out var name) ? name : "FIX ME (FirmwaresConfig.cs)");
-				return lvFirmwares.Groups[^1];
+				return lvFirmwares.Groups[lvFirmwares.Groups.Count - 1];
 			}
 
 			// we'll use this font for displaying the hash, so they don't look all jagged in a long list

src/BizHawk.Client.EmuHawk/config/GB/ColorChooserForm.cs

@@ -192,7 +192,9 @@ namespace BizHawk.Client.EmuHawk
 
 				try
 				{
-					lines.Add(line[..i], int.Parse(line[(i + 1)..]));
+					lines.Add(
+						line.Substring(startIndex: 0, length: i),
+						int.Parse(line.Substring(startIndex: i + 1)));
 				}
 				catch (FormatException)
 				{

src/BizHawk.Client.EmuHawk/config/GB/SameBoyColorChooserForm.cs

@@ -162,7 +162,9 @@ namespace BizHawk.Client.EmuHawk
 
 				try
 				{
-					lines.Add(line[..i], int.Parse(line[(i + 1)..]));
+					lines.Add(
+						line.Substring(startIndex: 0, length: i),
+						int.Parse(line.Substring(startIndex: i + 1)));
 				}
 				catch (FormatException)
 				{

src/BizHawk.Client.EmuHawk/debug/FirmwareAutopatchDebugToolForm.cs

@@ -23,7 +23,7 @@ namespace BizHawk.Client.EmuHawk.ForDebugging
 		public FirmwareAutopatchDebugToolForm()
 		{
 			static string LabelFragment(string hash)
-				=> $"{hash[..8]}... {FirmwareDatabase.FirmwareFilesByHash[hash].RecommendedName}";
+				=> $"{hash.Substring(startIndex: 0, length: 8)}... {FirmwareDatabase.FirmwareFilesByHash[hash].RecommendedName}";
 			List<(string Label, FirmwarePatchOption PatchOption)> patches = FirmwareDatabase.AllPatches
 				.Select(static fpo => ($"{LabelFragment(fpo.BaseHash)} --> {LabelFragment(fpo.TargetHash)}", fpo)).ToList();
 			patches.Sort(static (a, b) => string.CompareOrdinal(a.Label, b.Label));

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

@@ -451,7 +451,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = SelectedIndices.ToList();
 			if (indices.Count == 0
-				|| indices[^1] == MainForm.CheatList.Count - 1) // at end already
+				|| indices[indices.Count - 1] == MainForm.CheatList.Count - 1) // at end already
 			{
 				return;
 			}

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

@@ -1395,10 +1395,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			// and add HighlightedAddress if present
-			if (_highlightedAddress.HasValue)
+			if (_highlightedAddress is long l) addresses[addresses.Length - 1] = l;
-			{
-				addresses[^1] = _highlightedAddress.Value;
-			}
 
 			// these need to be sorted. it's not just for HighlightedAddress, _secondaryHighlightedAddresses can even be jumbled
 			Array.Sort(addresses);

src/BizHawk.Client.EmuHawk/tools/Lua/LuaConsole.cs

@@ -386,7 +386,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			while (LuaImp.ScriptList.Count > 0)
 			{
-				RemoveLuaFile(LuaImp.ScriptList[^1]);
+				RemoveLuaFile(LuaImp.ScriptList[LuaImp.ScriptList.Count - 1]);
 			}
 		}
 
@@ -1028,7 +1028,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = LuaListView.SelectedRows.ToList();
 			if (indices.Count == 0
-				|| indices[^1] == LuaImp.ScriptList.Count - 1) // at end already
+				|| indices[indices.Count - 1] == LuaImp.ScriptList.Count - 1) // at end already
 			{
 				return;
 			}
@@ -1333,7 +1333,7 @@ namespace BizHawk.Client.EmuHawk
 				var split = words[0].Split(Path.DirectorySeparatorChar);
 
 				luaListTemp.Add(LuaImp.ScriptList[i]);
-				luaListTemp[i].Name = split[^1];
+				luaListTemp[i].Name = split[split.Length - 1];
 			}
 
 			// Script, Path

src/BizHawk.Client.EmuHawk/tools/Macros/MacroInput.ButtonSelect.cs

@@ -58,10 +58,7 @@ namespace BizHawk.Client.EmuHawk
 					key = key.Replace($"{box.Text}|", "");
 				}
 			}
-
+			SelectedZone.InputKey = key.Substring(startIndex: 0, length: key.Length - 1); // drop final char
-			key = key[..^1];
-
-			SelectedZone.InputKey = key;
 		}
 
 		private void PositionBoxes()

src/BizHawk.Client.EmuHawk/tools/Macros/MovieZone.cs

@@ -28,7 +28,7 @@ namespace BizHawk.Client.EmuHawk
 			}
 
 			key = key.Replace("LogKey:", "").Replace("#", "");
-			key = key[..^1];
+			key = key.Substring(startIndex: 0, length: key.Length - 1); // drop last char
 
 			_inputKey = key;
 			Length = length;
@@ -41,7 +41,7 @@ namespace BizHawk.Client.EmuHawk
 			logGenerator.GenerateLogEntry(); // Reference and create all buttons.
 
 			string movieKey = logGenerator.GenerateLogKey().Replace("LogKey:", "").Replace("#", "");
-			movieKey = movieKey[..^1];
+			movieKey = movieKey.Substring(startIndex: 0, length: movieKey.Length - 1); // drop last char
 			if (key == movieKey)
 			{
 				for (int i = 0; i < length; i++)
@@ -239,7 +239,7 @@ namespace BizHawk.Client.EmuHawk
 			var lg = _movieSession.Movie.LogGeneratorInstance(_movieSession.MovieController);
 			string key = lg.GenerateLogKey();
 			key = key.Replace("LogKey:", "").Replace("#", "");
-			key = key[..^1];
+			key = key.Substring(startIndex: 0, length: key.Length - 1); // drop last char
 			string[] emuKeys = key.Split('|');
 			string[] macroKeys = _inputKey.Split('|');
 			foreach (var macro in macroKeys)

src/BizHawk.Client.EmuHawk/tools/TAStudio/PatternsForm.cs

@@ -302,7 +302,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (p[i] == lastValue)
 					{
-						_counts[^1]++;
+						_counts[_counts.Count - 1]++;
 					}
 					else
 					{
@@ -335,7 +335,7 @@ namespace BizHawk.Client.EmuHawk
 				{
 					if (p[i] == lastValue)
 					{
-						_counts[^1]++;
+						_counts[_counts.Count - 1]++;
 					}
 					else
 					{

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.ListView.cs

@@ -1313,7 +1313,7 @@ namespace BizHawk.Client.EmuHawk
 			else if (e.KeyCode == Keys.OemMinus || e.KeyCode == Keys.Subtract)
 			{
 				_axisTypedValue = _axisTypedValue.StartsWith('-')
-					? _axisTypedValue[1..]
+					? _axisTypedValue.Substring(startIndex: 1)
 					: $"-{_axisTypedValue}";
 			}
 			else if (e.KeyCode == Keys.Back)
@@ -1323,7 +1323,7 @@ namespace BizHawk.Client.EmuHawk
 					_axisTypedValue = value.ToString(NumberFormatInfo.InvariantInfo);
 				}
 
-				_axisTypedValue = _axisTypedValue[..^1];
+				_axisTypedValue = _axisTypedValue.Substring(startIndex: 0, length: _axisTypedValue.Length - 1); // drop last char
 				if (_axisTypedValue == "" || _axisTypedValue == "-")
 				{
 					value = 0f;

src/BizHawk.Client.EmuHawk/tools/TAStudio/TAStudio.MenuItems.cs

@@ -468,7 +468,7 @@ namespace BizHawk.Client.EmuHawk
 						{
 							_tasClipboard.Clear();
 							int linesToPaste = lines.Length;
-							if (lines[^1] == "") linesToPaste--;
+							if (lines[lines.Length - 1].Length is 0) linesToPaste--;
 							for (int i = 0; i < linesToPaste; i++)
 							{
 								var line = ControllerFromMnemonicStr(lines[i]);
@@ -510,7 +510,7 @@ namespace BizHawk.Client.EmuHawk
 						{
 							_tasClipboard.Clear();
 							int linesToPaste = lines.Length;
-							if (lines[^1] == "") linesToPaste--;
+							if (lines[lines.Length - 1].Length is 0) linesToPaste--;
 							for (int i = 0; i < linesToPaste; i++)
 							{
 								var line = ControllerFromMnemonicStr(lines[i]);

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

@@ -449,17 +449,16 @@ namespace BizHawk.Client.EmuHawk
 				BoolPatterns[i] = new AutoPatternBool(1, 1);
 			}
 
-			BoolPatterns[^2] = new AutoPatternBool(1, 0);
+			BoolPatterns[BoolPatterns.Length - 2] = new(1, 0);
-			BoolPatterns[^1] = new AutoPatternBool(
+			BoolPatterns[BoolPatterns.Length - 1] = new(Config.AutofireOn, Config.AutofireOff);
-				Config.AutofireOn, Config.AutofireOff);
 
 			for (int i = fStart; i < AxisPatterns.Length - 2; i++)
 			{
 				AxisPatterns[i] = new AutoPatternAxis(new[] { 1 });
 			}
 
-			AxisPatterns[^2] = new AutoPatternAxis(new[] { 1 });
+			AxisPatterns[AxisPatterns.Length - 2] = new([ 1 ]);
-			AxisPatterns[^1] = new AutoPatternAxis(1, Config.AutofireOn, 0, Config.AutofireOff);
+			AxisPatterns[AxisPatterns.Length - 1] = new(1, Config.AutofireOn, 0, Config.AutofireOff);
 
 			SetUpToolStripColumns();
 		}

src/BizHawk.Client.EmuHawk/tools/Watch/RamWatch.cs

@@ -928,7 +928,7 @@ namespace BizHawk.Client.EmuHawk
 		{
 			var indices = SelectedIndices.ToList();
 			if (indices.Count == 0
-				|| indices[^1] == _watches.Count - 1) // at end already
+				|| indices[indices.Count - 1] == _watches.Count - 1) // at end already
 			{
 				return;
 			}

src/BizHawk.Common/Log.cs

@@ -39,7 +39,9 @@ namespace BizHawk.Common
 		}
 
 		// -------------- Logging Action Configuration --------------
-		public static readonly Action<string> LogAction = DefaultLogger;
+#pragma warning disable CA2211 // public field
+		public static Action<string> LogAction = DefaultLogger;
+#pragma warning restore CA2211
 
 		// NOTEs are only logged if the domain is enabled.
 		// ERRORs are logged regardless.

src/BizHawk.Emulation.Cores/CPUs/HuC6280/HuC6280_CDL.cs

@@ -24,7 +24,7 @@ namespace BizHawk.Emulation.Cores.Components.H6280
 					{
 						string dis = DisassembleExt(
 							0,
-							out int unused,
+							out _,
 							addr => md.PeekByte(addr + i),
 							addr => md.PeekUshort(addr + i, bigEndian: false));
 						w.WriteLine("0x{0:x8}: {1}", i, dis);

src/BizHawk.Emulation.Cores/Computers/Commodore64/Media/G64.cs

@@ -100,9 +100,8 @@ namespace BizHawk.Emulation.Cores.Computers.Commodore64.Media
 						offsets.Add((int)trackMem.Length);
 						densities.Add(trackDensities[trackIndex]);
 
-						var data = trackData[trackIndex];
 						var buffer = Enumerable.Repeat(dataFillerValue, trackMaxLength).ToArray();
-						var dataBytes = data.Select(d => unchecked(d)).ToArray();
+						var dataBytes = trackData[trackIndex];
 						Array.Copy(dataBytes, buffer, dataBytes.Length);
 						trackMemWriter.Write((ushort)dataBytes.Length);
 						trackMemWriter.Write(buffer);

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/Pentagon128K/Pentagon128.Port.cs

@@ -46,9 +46,8 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // if this is detected just return the kempston byte
             if (lowByte == 0x1f)
             {
-                if (LocateUniqueJoystick(JoystickType.Kempston) != null)
+                //TODO lines swapped?
-                    return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston)).JoyLine;
+                if (LocateUniqueJoystick(JoystickType.Kempston) is KempstonJoystick j) return (byte) j.JoyLine;
-
                 InputRead = true;
             }
             else

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum128K/ZX128.Port.cs

@@ -45,14 +45,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // Kempston joystick input takes priority over keyboard input
             // if this is detected just return the kempston byte
             if (lowByte == 0x1f)
-            {
-                if (LocateUniqueJoystick(JoystickType.Kempston) != null)
             {
                 InputRead = true;
-					return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston)).JoyLine;
+                if (LocateUniqueJoystick(JoystickType.Kempston) is KempstonJoystick j) return (byte) j.JoyLine;
-				}
-
-				InputRead = true;
             }
             else
             {

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum128KPlus2a/ZX128Plus2a.Port.cs

@@ -26,14 +26,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // Kempston joystick input takes priority over all keyboard input
             // if this is detected just return the kempston byte
             if (lowByte == 0x1f)
-            {
-                if (LocateUniqueJoystick(JoystickType.Kempston) != null)
             {
                 InputRead = true;
-					return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston)).JoyLine;
+                if (LocateUniqueJoystick(JoystickType.Kempston) is KempstonJoystick j) return (byte) j.JoyLine;
-				}
-
-				InputRead = true;
             }
             else
             {

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum128KPlus3/ZX128Plus3.Port.cs

@@ -26,14 +26,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // Kempston joystick input takes priority over all keyboard input
             // if this is detected just return the kempston byte
             if (lowByte == 0x1f)
-            {
-                if (LocateUniqueJoystick(JoystickType.Kempston) != null)
             {
                 InputRead = true;
-					return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston)).JoyLine;
+                if (LocateUniqueJoystick(JoystickType.Kempston) is KempstonJoystick j) return (byte) j.JoyLine;
-				}
-
-				InputRead = true;
             }
             else if (UPDDiskDevice.ReadPort(port, ref result))
             {

src/BizHawk.Emulation.Cores/Computers/SinclairSpectrum/Machine/ZXSpectrum48K/ZX48.Port.cs

@@ -22,14 +22,9 @@ namespace BizHawk.Emulation.Cores.Computers.SinclairSpectrum
             // if this is detected just return the kempston byte
             if (lowByte == 0x1f)
             {
-                if (LocateUniqueJoystick(JoystickType.Kempston) != null)
-				{
-					InputRead = true;
-					return (byte)((KempstonJoystick)LocateUniqueJoystick(JoystickType.Kempston)).JoyLine;
-				}
-
                 // not a lag frame
                 InputRead = true;
+                if (LocateUniqueJoystick(JoystickType.Kempston) is KempstonJoystick j) return (byte) j.JoyLine;
             }
             // Even ports always address the ULA
             else if (lowBitReset)