Reject invalid view-model mapping contracts (SVL0006)

README.md

@@ -96,6 +96,7 @@ This generates `DashboardModel -> DashboardScreen` even though neither type foll
 Contract discovery has these constraints:
 
 - each configured contract must be an open generic type with exactly one type parameter;
+- invalid configured contracts are ignored and produce the `SVL0006` error;
 - the contract may be an interface or a base class, including one inherited indirectly;
 - discovered views must be concrete, non-generic types from the current compilation;
 - discovered views must derive from `UserControl`, `Window`, or a type configured through `StaticViewLocatorAdditionalViewBaseTypes`;
@@ -213,6 +214,7 @@ The solution builds the same complete AXAML sample against both distributions. `
 | `SVL0003` | Error | More than one inferred view maps to the same view model. |
 | `SVL0004` | Error | A mapped view is inaccessible, abstract, or has no accessible constructor callable without arguments. |
 | `SVL0005` | Error | The annotated locator is nested, static, file-local, or not partial. |
+| `SVL0006` | Error | A configured mapping contract is not an open generic interface or class with exactly one type parameter. |
 
 ### Attribute options
 

StaticViewLocator.Tests/StaticViewLocatorGeneratorSnapshotTests.cs

@@ -9,6 +9,35 @@ namespace StaticViewLocator.Tests;
 
 public class StaticViewLocatorGeneratorSnapshotTests
 {
+    [Fact]
+    public void ReportsInvalidMappingContracts()
+    {
+        const string input = """
+using StaticViewLocator;
+
+namespace TestApp;
+
+public interface IInvalidContract { }
+public interface IViewFor<TViewModel> { }
+
+[StaticViewLocator(ViewModelMappingContracts = new[]
+{
+    typeof(IInvalidContract),
+    typeof(IViewFor<string>)
+})]
+public partial class ViewLocator { }
+""";
+
+        var result = StaticViewLocatorGeneratorVerifier.RunGenerator(input);
+        var diagnostics = result.GeneratorDiagnostics
+            .Where(static item => item.Id == "SVL0006")
+            .ToArray();
+
+        Assert.Equal(2, diagnostics.Length);
+        Assert.Contains(diagnostics, static item => item.GetMessage().Contains("TestApp.IInvalidContract", StringComparison.Ordinal));
+        Assert.Contains(diagnostics, static item => item.GetMessage().Contains("TestApp.IViewFor<string>", StringComparison.Ordinal));
+    }
+
     [Fact]
     public async Task GeneratesFactoriesForConstructorsCallableWithoutArguments()
     {

StaticViewLocator/AnalyzerReleases.Unshipped.md

@@ -9,3 +9,4 @@ SVL0002 | StaticViewLocator.Generation | Error | Source member is incompatible w
 SVL0003 | StaticViewLocator.Generation | Error | View mapping is ambiguous
 SVL0004 | StaticViewLocator.Generation | Error | Mapped view cannot be constructed
 SVL0005 | StaticViewLocator.Generation | Error | Locator type cannot be extended by generated source
+SVL0006 | StaticViewLocator.Generation | Error | Configured view-model mapping contract is invalid

StaticViewLocator/StaticViewLocatorGenerator.Adapters.cs

@@ -60,6 +60,15 @@ public sealed partial class StaticViewLocatorGenerator
         isEnabledByDefault: true,
         description: "Generated partial declarations cannot extend static or file-local locator classes.");
 
+    private static readonly DiagnosticDescriptor InvalidMappingContract = new(
+        id: "SVL0006",
+        title: "Configured view-model mapping contract is invalid",
+        messageFormat: "Mapping contract '{0}' must be an open generic interface or class with exactly one type parameter",
+        category: "StaticViewLocator.Generation",
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true,
+        description: "Configured contract discovery requires an open generic interface or class with exactly one type parameter.");
+
     private static Dictionary<INamedTypeSymbol, INamedTypeSymbol> GetReactiveUIMappings(
         Compilation compilation,
         HashSet<INamedTypeSymbol> viewBaseTypes,

StaticViewLocator/StaticViewLocatorGenerator.cs

@@ -1194,7 +1194,7 @@ private static Dictionary<INamedTypeSymbol, INamedTypeSymbol> GetInferredMapping
         ICollection<Diagnostic> diagnostics,
         HashSet<INamedTypeSymbol> ambiguousViewModels)
     {
-        var contracts = GetViewModelMappingContracts(locatorSymbol);
+        var contracts = GetViewModelMappingContracts(locatorSymbol, diagnostics);
         var mappings = new Dictionary<INamedTypeSymbol, INamedTypeSymbol>(SymbolEqualityComparer.Default);
         if (contracts.Count == 0)
         {
@@ -1247,7 +1247,9 @@ private static Dictionary<INamedTypeSymbol, INamedTypeSymbol> GetInferredMapping
         return mappings;
     }
 
-    private static HashSet<INamedTypeSymbol> GetViewModelMappingContracts(INamedTypeSymbol locatorSymbol)
+    private static HashSet<INamedTypeSymbol> GetViewModelMappingContracts(
+        INamedTypeSymbol locatorSymbol,
+        ICollection<Diagnostic> diagnostics)
     {
         var contracts = new HashSet<INamedTypeSymbol>(SymbolEqualityComparer.Default);
         var locatorAttribute = locatorSymbol.GetAttributes()
@@ -1266,10 +1268,23 @@ private static HashSet<INamedTypeSymbol> GetViewModelMappingContracts(INamedType
 
             foreach (var value in argument.Value.Values)
             {
-                if (value.Value is INamedTypeSymbol contract && contract.Arity == 1)
+                if (value.Value is not INamedTypeSymbol contract)
+                {
+                    continue;
+                }
+
+                if (contract.Arity == 1 &&
+                    (contract.TypeKind == TypeKind.Interface || contract.TypeKind == TypeKind.Class) &&
+                    contract.IsUnboundGenericType)
                 {
                     contracts.Add(contract.OriginalDefinition);
+                    continue;
                 }
+
+                diagnostics.Add(Diagnostic.Create(
+                    InvalidMappingContract,
+                    GetDiagnosticLocation(locatorSymbol),
+                    contract.ToDisplayString(SymbolDisplayFormat.CSharpErrorMessageFormat)));
             }
         }