Add `BizHawk.Analyzer` project

Common.ruleset

@@ -1,5 +1,18 @@
 <?xml version="1.0"?>
 <RuleSet Name="BizHawk Rules" Description="Applies to all projects in the solution -- or, it will eventually." ToolsVersion="14.0">
+	<Rules AnalyzerId="BizHawk.Analyzer" RuleNamespace="BizHawk.Analyzer">
+		<!-- Do not use anonymous delegates -->
+		<Rule Id="BHI1001" Action="Hidden" />
+
+		<!-- Do not use anonymous types (classes) -->
+		<Rule Id="BHI1002" Action="Hidden" />
+
+		<!-- Do not use query expression syntax -->
+		<Rule Id="BHI1003" Action="Error" />
+
+		<!-- Verbatim interpolated strings should begin $@, not @$ -->
+		<Rule Id="BHI1004" Action="Error" />
+	</Rules>
 	<Rules AnalyzerId="DocumentationAnalyzers" RuleNamespace="DocumentationAnalyzers.StyleRules">
 		<!-- Place text in paragraphs -->
 		<Rule Id="DOC100" Action="Hidden" />

ExternalProjects/BizHawk.Analyzer/BizHawk.Analyzer.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+	<PropertyGroup>
+		<TargetFramework>netstandard2.0</TargetFramework>
+	</PropertyGroup>
+	<Import Project="../../Common.props" />
+	<ItemGroup>
+		<PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.2" PrivateAssets="all" />
+		<PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="3.8.0" PrivateAssets="all" />
+	</ItemGroup>
+	<Target Name="PostBuild" AfterTargets="PostBuildEvent">
+		<Copy SourceFiles="$(OutputPath)BizHawk.Analyzer.dll" DestinationFolder="$(ProjectDir)../../References/" />
+	</Target>
+</Project>

ExternalProjects/BizHawk.Analyzer/HawkSourceAnalyzer.cs

@@ -0,0 +1,79 @@
+namespace BizHawk.Analyzers;
+
+using System.Collections.Immutable;
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public class HawkSourceAnalyzer : DiagnosticAnalyzer
+{
+	private static readonly DiagnosticDescriptor DiagInterpStringIsDollarAt = new(
+		id: "BHI1004",
+		title: "Verbatim interpolated strings should begin $@, not @$",
+		messageFormat: "Swap @ and $ on interpolated string",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Error,
+		isEnabledByDefault: true);
+
+	private static readonly DiagnosticDescriptor DiagNoAnonClasses = new(
+		id: "BHI1002",
+		title: "Do not use anonymous types (classes)",
+		messageFormat: "Replace anonymous class with tuple or explicit type",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Error,
+		isEnabledByDefault: true);
+
+	private static readonly DiagnosticDescriptor DiagNoAnonDelegates = new(
+		id: "BHI1001",
+		title: "Do not use anonymous delegates",
+		messageFormat: "Replace anonymous delegate with lambda or local method",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Error,
+		isEnabledByDefault: true);
+
+	private static readonly DiagnosticDescriptor DiagNoQueryExpression = new(
+		id: "BHI1003",
+		title: "Do not use query expression syntax",
+		messageFormat: "Use method chain for LINQ instead of query expression syntax",
+		category: "Usage",
+		defaultSeverity: DiagnosticSeverity.Error,
+		isEnabledByDefault: true);
+
+	public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics { get; } = ImmutableArray.Create(
+		DiagInterpStringIsDollarAt,
+		DiagNoAnonClasses,
+		DiagNoAnonDelegates,
+		DiagNoQueryExpression);
+
+	public override void Initialize(AnalysisContext context)
+	{
+		context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.None);
+		context.EnableConcurrentExecution();
+		context.RegisterSyntaxNodeAction(
+			static snac =>
+			{
+				switch (snac.Node)
+				{
+					case AnonymousMethodExpressionSyntax:
+						snac.ReportDiagnostic(Diagnostic.Create(DiagNoAnonDelegates, snac.Node.GetLocation()));
+						break;
+					case AnonymousObjectCreationExpressionSyntax:
+						snac.ReportDiagnostic(Diagnostic.Create(DiagNoAnonClasses, snac.Node.GetLocation()));
+						break;
+					case InterpolatedStringExpressionSyntax ises:
+						if (ises.StringStartToken.Text[0] is '@') snac.ReportDiagnostic(Diagnostic.Create(DiagInterpStringIsDollarAt, ises.GetLocation()));
+						break;
+					case QueryExpressionSyntax:
+						snac.ReportDiagnostic(Diagnostic.Create(DiagNoQueryExpression, snac.Node.GetLocation()));
+						break;
+				}
+			},
+			SyntaxKind.AnonymousObjectCreationExpression,
+			SyntaxKind.AnonymousMethodExpression,
+			SyntaxKind.InterpolatedStringExpression,
+			SyntaxKind.QueryExpression);
+	}
+}

src/MainSlnCommon.props

@@ -12,6 +12,7 @@
 	</PropertyGroup>
 	<ItemGroup>
 		<AdditionalFiles Include="$(ProjectDir)../../.stylecop.json" />
+		<Analyzer Include="$(ProjectDir)../../References/BizHawk.Analyzer.dll" />
 		<Analyzer Include="$(ProjectDir)../../References/BizHawk.SrcGen.ReflectionCache.dll" />
 	</ItemGroup>
 </Project>