WIP Add Analyzer to prevent empty ArraySegment collection expression

Author: YoshiRulz

ExternalProjects/BizHawk.Analyzer/BrokenCollectionExpressionAnalyzer.cs

@@ -0,0 +1,35 @@
+namespace BizHawk.Analyzers;
+
+using System.Collections.Immutable;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class BrokenCollectionExpressionAnalyzer : DiagnosticAnalyzer
+{
+	private static readonly DiagnosticDescriptor DiagBrokenCollectionExpression = new(
+		id: "BHI1234",
+		title: "don't this",
+		messageFormat: "don't this",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Warning,
+		isEnabledByDefault: true);
+
+	public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; }
+		= ImmutableArray.Create(/*HawkSourceAnalyzer.DiagWTF,*/ DiagBrokenCollectionExpression);
+
+	public override void Initialize(AnalysisContext context)
+	{
+		context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+		context.EnableConcurrentExecution();
+		context.RegisterCompilationStartAction(initContext =>
+		{
+			var arraySegmentSym = initContext.Compilation.GetTypeByMetadataName("System.ArraySegment`1")!;
+			initContext.RegisterOperationAction(
+				oac =>
+				{
+					var operation = (ICollectionExpressionOperation) oac.Operation;
+					if (arraySegmentSym.Matches(operation.Type)) DiagBrokenCollectionExpression.ReportAt(operation, oac);
+				},
+				OperationKind.CollectionExpression);
+		});
+	}
+}