Rework witness type generation scheme. (#63)

* Rework witness type generation scheme.

* Extend witness type support to structs.

* Add detection for static class GenerateShape annotations.

src/PolyType.SourceGenerator/Model/TypeDeclarationModel.cs

@@ -10,6 +10,6 @@ public record TypeDeclarationModel
     public required ImmutableEquatableArray<string> ContainingTypes { get; init; }
     public required string SourceFilenamePrefix { get; init; }
     public required string? Namespace { get; init; }
-    public required bool ImplementsITypeShapeProvider { get; init; }
+    public required bool IsWitnessTypeDeclaration { get; init; }
     public required ImmutableEquatableSet<TypeId> ShapeableOfTImplementations { get; init; }
 }

src/PolyType.SourceGenerator/Parser/Parser.Diagnostics.cs

@@ -7,7 +7,7 @@ public sealed partial class Parser
     private static DiagnosticDescriptor TypeNotSupported { get; } = new DiagnosticDescriptor(
         id: "TS0001",
         title: "Type shape generation not supported for type.",
-        messageFormat: "Type shape generation not supported for type '{0}'.",
+        messageFormat: "The type '{0}' is not supported for PolyType generation.",
         category: "PolyType.SourceGenerator",
         defaultSeverity: DiagnosticSeverity.Warning,
         isEnabledByDefault: true);
@@ -51,4 +51,12 @@ public sealed partial class Parser
         category: "PolyType.SourceGenerator",
         defaultSeverity: DiagnosticSeverity.Warning,
         isEnabledByDefault: true);
+
+    private static DiagnosticDescriptor GeneratedTypeIsStatic { get; } = new DiagnosticDescriptor(
+        id: "TS0007",
+        title: "Types annotated with GenerateShapeAttribute cannot be static.",
+        messageFormat: "The type '{0}' that has been annotated with GenerateShapeAttribute cannot be static.",
+        category: "PolyType.SourceGenerator",
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true);
 }

src/PolyType.SourceGenerator/Parser/Parser.cs

@@ -25,7 +25,7 @@ public sealed partial class Parser : TypeDataModelGenerator
 
     // All types used as generic parameters so we must exclude ref structs.
     protected override bool IsSupportedType(ITypeSymbol type)
-        => base.IsSupportedType(type) && !type.IsRefLikeType;
+        => base.IsSupportedType(type) && !type.IsRefLikeType && !type.IsStatic;
 
     // Erase nullable annotations and tuple labels from generated types.
     protected override ITypeSymbol NormalizeType(ITypeSymbol type)
@@ -186,6 +186,12 @@ private ImmutableEquatableArray<TypeDeclarationModel> IncludeTypesUsingGenerateS
             return null;
         }
 
+        if (context.TypeSymbol.IsStatic)
+        {
+            ReportDiagnostic(GeneratedTypeIsStatic, declarationSyntax.GetLocation(), context.TypeSymbol.ToDisplayString());
+            return null;
+        }
+
         TypeId typeId = CreateTypeId(context.TypeSymbol);
         HashSet<TypeId>? shapeableOfTImplementations = null;
         bool isWitnessTypeDeclaration = false;
@@ -235,7 +241,7 @@ private ImmutableEquatableArray<TypeDeclarationModel> IncludeTypesUsingGenerateS
             ContainingTypes = parentStack?.ToImmutableEquatableArray() ?? [],
             Namespace = FormatNamespace(context.TypeSymbol),
             SourceFilenamePrefix = context.TypeSymbol.ToDisplayString(RoslynHelpers.QualifiedNameOnlyFormat),
-            ImplementsITypeShapeProvider = isWitnessTypeDeclaration,
+            IsWitnessTypeDeclaration = isWitnessTypeDeclaration,
             ShapeableOfTImplementations = shapeableOfTImplementations?.ToImmutableEquatableSet() ?? [],
         };
 
@@ -345,7 +351,7 @@ private static TypeId CreateTypeId(ITypeSymbol type)
         Namespace = "PolyType.SourceGenerator",
         SourceFilenamePrefix = "PolyType.SourceGenerator.ShapeProvider",
         TypeDeclarationHeader = "internal sealed partial class ShapeProvider",
-        ImplementsITypeShapeProvider = true,
+        IsWitnessTypeDeclaration = false,
         ContainingTypes = [],
         ShapeableOfTImplementations = [],
     };

src/PolyType.SourceGenerator/SourceFormatter/SourceFormatter.ITypeShapeProvider.cs

@@ -71,16 +71,16 @@ private SourceText FormatIShapeableOfTStub(TypeDeclarationModel typeDeclaration,
         return writer.ToSourceText();
     }
 
-    private static SourceText FormatITypeShapeProviderStub(TypeDeclarationModel typeDeclaration, TypeShapeProviderModel provider)
+    private static SourceText FormatWitnessTypeMainFile(TypeDeclarationModel typeDeclaration, TypeShapeProviderModel provider)
     {
         var writer = new SourceWriter();
         StartFormatSourceFile(writer, typeDeclaration);
 
         writer.WriteLine($$"""
-            {{typeDeclaration.TypeDeclarationHeader}} : global::PolyType.ITypeShapeProvider
+            {{typeDeclaration.TypeDeclarationHeader}}
             {
-                global::PolyType.Abstractions.ITypeShape? global::PolyType.ITypeShapeProvider.GetShape(global::System.Type type) 
-                    => {{provider.ProviderDeclaration.Id.FullyQualifiedName}}.{{ProviderSingletonProperty}}.GetShape(type);
+                /// <summary>Gets the source generated <see cref="global::PolyType.ITypeShapeProvider"/> corresponding to the current witness type.</summary>
+                public static global::PolyType.ITypeShapeProvider ShapeProvider => {{provider.ProviderDeclaration.Id.FullyQualifiedName}}.{{ProviderSingletonProperty}};
             }
             """);
 

src/PolyType.SourceGenerator/SourceFormatter/SourceFormatter.Type.cs

@@ -7,7 +7,7 @@ namespace PolyType.SourceGenerator;
 
 internal sealed partial class SourceFormatter
 {
-    private SourceText FormatType(TypeShapeProviderModel provider, TypeShapeModel type)
+    private SourceText FormatProvidedType(TypeShapeProviderModel provider, TypeShapeModel type)
     {
         string generatedPropertyType = $"global::PolyType.Abstractions.ITypeShape<{type.Type.FullyQualifiedName}>";
         string generatedFactoryMethodName = $"__Create_{type.SourceIdentifier}";

src/PolyType.SourceGenerator/SourceFormatter/SourceFormatter.cs

@@ -23,20 +23,20 @@ public static void GenerateSourceFiles(SourceProductionContext context, TypeShap
     private void AddAllSourceFiles(SourceProductionContext context, TypeShapeProviderModel provider)
     {
         context.CancellationToken.ThrowIfCancellationRequested();
-        context.AddSource($"{provider.ProviderDeclaration.SourceFilenamePrefix}.g.cs", FormatMainFile(provider));
+        context.AddSource($"{provider.ProviderDeclaration.SourceFilenamePrefix}.g.cs", FormatProviderMainFile(provider));
         context.AddSource($"{provider.ProviderDeclaration.SourceFilenamePrefix}.ITypeShapeProvider.g.cs", FormatProviderInterfaceImplementation(provider));
 
         foreach (TypeShapeModel type in provider.ProvidedTypes.Values)
         {
             context.CancellationToken.ThrowIfCancellationRequested();
-            context.AddSource($"{provider.ProviderDeclaration.SourceFilenamePrefix}.{type.SourceIdentifier}.g.cs", FormatType(provider, type));
+            context.AddSource($"{provider.ProviderDeclaration.SourceFilenamePrefix}.{type.SourceIdentifier}.g.cs", FormatProvidedType(provider, type));
         }
 
         foreach (TypeDeclarationModel typeDeclaration in provider.AnnotatedTypes)
         {
-            if (typeDeclaration.ImplementsITypeShapeProvider)
+            if (typeDeclaration.IsWitnessTypeDeclaration)
             {
-                context.AddSource($"{typeDeclaration.SourceFilenamePrefix}.ITypeShapeProvider.g.cs", FormatITypeShapeProviderStub(typeDeclaration, provider));
+                context.AddSource($"{typeDeclaration.SourceFilenamePrefix}.g.cs", FormatWitnessTypeMainFile(typeDeclaration, provider));
             }
 
             foreach (TypeId typeToImplement in typeDeclaration.ShapeableOfTImplementations)
@@ -50,7 +50,7 @@ private void AddAllSourceFiles(SourceProductionContext context, TypeShapeProvide
         }
     }
 
-    private static SourceText FormatMainFile(TypeShapeProviderModel provider)
+    private static SourceText FormatProviderMainFile(TypeShapeProviderModel provider)
     {
         var writer = new SourceWriter();
         StartFormatSourceFile(writer, provider.ProviderDeclaration);

src/PolyType/GenerateShapeAttribute.cs

@@ -14,5 +14,5 @@ public sealed class GenerateShapeAttribute : Attribute;
 /// implementation that includes <typeparamref name="T"/>.
 /// </summary>
 /// <typeparam name="T">The type for which shape metadata will be generated.</typeparam>
-[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = false)]
+[AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, AllowMultiple = true, Inherited = false)]
 public sealed class GenerateShapeAttribute<T> : Attribute;

tests/PolyType.SourceGenerator.UnitTests/CompilationTests.cs

@@ -309,19 +309,27 @@ internal record MyPoco(int Value);
         Assert.Empty(result.Diagnostics);
     }
 
-    [Fact]
-    public static void RecordWitnessType_NoErrors()
+    [Theory]
+    [InlineData("partial class")]
+    [InlineData("sealed partial class")]
+    [InlineData("partial struct")]
+    [InlineData("partial record")]
+    [InlineData("sealed partial record")]
+    [InlineData("partial record struct")]
+    public static void SupportedWitnessTypeKinds_NoErrors(string kind)
     {
-        Compilation compilation = CompilationHelpers.CreateCompilation("""
+        Compilation compilation = CompilationHelpers.CreateCompilation($"""
             using PolyType;
             using PolyType.Abstractions;
 
-            ITypeShape<MyPoco> shape = TypeShapeProvider.Resolve<MyPoco, Witness>();
+            ITypeShape<MyPoco> shape;
+            shape = TypeShapeProvider.Resolve<MyPoco, Witness>();
+            shape = TypeShapeProvider.Resolve<MyPoco>(Witness.ShapeProvider);
 
             record MyPoco(string[] Values);
 
             [GenerateShape<MyPoco>]
-            partial record Witness;
+            {kind} Witness;
             """, outputKind: OutputKind.ConsoleApplication);
 
         PolyTypeSourceGeneratorResult result = CompilationHelpers.RunPolyTypeSourceGenerator(compilation);

tests/PolyType.SourceGenerator.UnitTests/DiagnosticTests.cs

@@ -210,4 +210,46 @@ public MyPoco(int value) { }
         Assert.Equal((9, 11), diagnostic.Location.GetStartPosition());
         Assert.Equal((9, 17), diagnostic.Location.GetEndPosition());
     }
+
+    [Fact]
+    public static void GenerateShapeOnStaticClass_ProducesError()
+    {
+        Compilation compilation = CompilationHelpers.CreateCompilation("""
+           using PolyType;
+
+           [GenerateShape]
+           static partial class MyClass;
+           """);
+
+        PolyTypeSourceGeneratorResult result = CompilationHelpers.RunPolyTypeSourceGenerator(compilation, disableDiagnosticValidation: true);
+
+        Diagnostic diagnostic = Assert.Single(result.Diagnostics);
+
+        Assert.Equal("TS0007", diagnostic.Id);
+        Assert.Equal(DiagnosticSeverity.Error, diagnostic.Severity);
+        Assert.Equal((2, 0), diagnostic.Location.GetStartPosition());
+        Assert.Equal((3, 29), diagnostic.Location.GetEndPosition());
+    }
+
+    [Fact]
+    public static void GenerateShapeOfTOnStaticClass_ProducesError()
+    {
+        Compilation compilation = CompilationHelpers.CreateCompilation("""
+           using PolyType;
+
+           [GenerateShape<MyPoco>]
+           static partial class Witness;
+
+           record MyPoco;
+           """);
+
+        PolyTypeSourceGeneratorResult result = CompilationHelpers.RunPolyTypeSourceGenerator(compilation, disableDiagnosticValidation: true);
+
+        Diagnostic diagnostic = Assert.Single(result.Diagnostics);
+
+        Assert.Equal("TS0007", diagnostic.Id);
+        Assert.Equal(DiagnosticSeverity.Error, diagnostic.Severity);
+        Assert.Equal((2, 0), diagnostic.Location.GetStartPosition());
+        Assert.Equal((3, 29), diagnostic.Location.GetEndPosition());
+    }
 }

tests/PolyType.Tests/TypeShapeProviderTests.cs

@@ -666,12 +666,20 @@ public sealed class TypeShapeProviderTests_ReflectionEmit() : TypeShapeProviderT
 public sealed class TypeShapeProviderTests_NoNullableAnnotations() : TypeShapeProviderTests(RefectionProviderUnderTest.NoNullableAnnotations);
 public sealed class TypeShapeProviderTests_SourceGen() : TypeShapeProviderTests(SourceGenProviderUnderTest.Default)
 {
+    [Fact]
+    public void WitnessType_ShapeProvider_IsSingleton()
+    {
+        ITypeShapeProvider provider = SourceGenProvider.ShapeProvider;
+
+        Assert.NotNull(provider);
+        Assert.Same(provider, SourceGenProvider.ShapeProvider);
+    }
+
     [Theory]
     [MemberData(nameof(TestTypes.GetTestCases), MemberType = typeof(TestTypes))]
-    public void WitnessType_ImplementsITypeShapeProvider(ITestCase testCase)
+    public void WitnessType_ShapeProvider_MatchesGeneratedShapes(ITestCase testCase)
     {
-        SourceGenProvider provider = new();
-        ITypeShapeProvider shapeProvider = Assert.IsAssignableFrom<ITypeShapeProvider>(provider);
-        Assert.Same(testCase.DefaultShape, shapeProvider.GetShape(testCase.Type));
+        Assert.Same(SourceGenProvider.ShapeProvider, testCase.DefaultShape.Provider);
+        Assert.Same(testCase.DefaultShape, SourceGenProvider.ShapeProvider.GetShape(testCase.Type));
     }
 }