Refactor (#94)

CliFx.Analyzers/ParameterMustHaveValidConverterAnalyzer.cs

@@ -0,0 +1,55 @@
+using System.Linq;
+using CliFx.Analyzers.ObjectModel;
+using CliFx.Analyzers.Utils.Extensions;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace CliFx.Analyzers
+{
+    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public class ParameterMustHaveValidConverterAnalyzer : AnalyzerBase
+    {
+        public ParameterMustHaveValidConverterAnalyzer()
+            : base(
+                $"Parameter converters must derive from `{SymbolNames.CliFxBindingConverterClass}`",
+                $"Converter specified for this parameter must derive from `{SymbolNames.CliFxBindingConverterClass}`.")
+        {
+        }
+
+        private void Analyze(SyntaxNodeAnalysisContext context)
+        {
+            if (context.Node is not PropertyDeclarationSyntax propertyDeclaration)
+                return;
+
+            var property = context.SemanticModel.GetDeclaredSymbol(propertyDeclaration);
+            if (property is null)
+                return;
+
+            var parameter = CommandParameterSymbol.TryResolve(property);
+            if (parameter is null)
+                return;
+
+            if (parameter.ConverterType is null)
+                return;
+
+            // We check against an internal interface because checking against a generic class is a pain
+            var converterImplementsInterface = parameter
+                .ConverterType
+                .AllInterfaces
+                .Any(s => s.DisplayNameMatches(SymbolNames.CliFxBindingConverterInterface));
+
+            if (!converterImplementsInterface)
+            {
+                context.ReportDiagnostic(CreateDiagnostic(propertyDeclaration.GetLocation()));
+            }
+        }
+
+        public override void Initialize(AnalysisContext context)
+        {
+            base.Initialize(context);
+            context.RegisterSyntaxNodeAction(Analyze, SyntaxKind.PropertyDeclaration);
+        }
+    }
+}