[Binding SG] Refactor data models (#24462)

* Extracted PathPart into separate file

* Changed BindingSGUtilities to extension methods

* Split GeneratorDataModels into meaningful parts

src/Controls/src/BindingSourceGen/BindingInvocationDescription.cs

@@ -0,0 +1,53 @@
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Text;
+
+namespace Microsoft.Maui.Controls.BindingSourceGen;
+
+public sealed record BindingInvocationDescription(
+	InterceptorLocation Location,
+	TypeDescription SourceType,
+	TypeDescription PropertyType,
+	EquatableArray<IPathPart> Path,
+	SetterOptions SetterOptions,
+	bool NullableContextEnabled,
+	InterceptedMethodType MethodType);
+
+public sealed record SourceCodeLocation(string FilePath, TextSpan TextSpan, LinePositionSpan LineSpan)
+{
+	public static SourceCodeLocation? CreateFrom(Location location)
+		=> location.SourceTree is null
+			? null
+			: new SourceCodeLocation(location.SourceTree.FilePath, location.SourceSpan, location.GetLineSpan().Span);
+
+	public Location ToLocation()
+	{
+		return Location.Create(FilePath, TextSpan, LineSpan);
+	}
+
+	public InterceptorLocation ToInterceptorLocation()
+	{
+		return new InterceptorLocation(FilePath, LineSpan.Start.Line + 1, LineSpan.Start.Character + 1);
+	}
+}
+
+public sealed record InterceptorLocation(string FilePath, int Line, int Column);
+
+public sealed record TypeDescription(
+	string GlobalName,
+	bool IsValueType = false,
+	bool IsNullable = false,
+	bool IsGenericParameter = false)
+{
+	public override string ToString()
+		=> IsNullable
+			? $"{GlobalName}?"
+			: GlobalName;
+}
+
+public enum InterceptedMethodType
+{
+	SetBinding,
+	Create
+}
+
+public sealed record SetterOptions(bool IsWritable, bool AcceptsNullValue = false);

src/Controls/src/BindingSourceGen/BindingSourceGenerator.cs

@@ -4,6 +4,12 @@
 
 namespace Microsoft.Maui.Controls.BindingSourceGen;
 
+public class TrackingNames
+{
+	public const string BindingsWithDiagnostics = nameof(BindingsWithDiagnostics);
+	public const string Bindings = nameof(Bindings);
+}
+
 [Generator(LanguageNames.CSharp)]
 public class BindingSourceGenerator : IIncrementalGenerator
 {
@@ -124,7 +130,7 @@ private static Result<BindingInvocationDescription> GetBindingForGeneration(Gene
 			return Result<BindingInvocationDescription>.Failure(DiagnosticsFactory.LambdaResultCannotBeResolved(lambdaBodyResult.Value.GetLocation()));
 		}
 
-		if (!BindingGenerationUtilities.IsAccessible(lambdaParamType.DeclaredAccessibility))
+		if (!lambdaParamType.IsAccessible())
 		{
 			return Result<BindingInvocationDescription>.Failure(DiagnosticsFactory.UnaccessibleTypeUsedAsLambdaParameter(lambdaBodyResult.Value.GetLocation()));
 		}
@@ -138,8 +144,8 @@ private static Result<BindingInvocationDescription> GetBindingForGeneration(Gene
 
 		var binding = new BindingInvocationDescription(
 			Location: sourceCodeLocation.ToInterceptorLocation(),
-			SourceType: BindingGenerationUtilities.CreateTypeDescription(lambdaParamType, enabledNullable),
-			PropertyType: BindingGenerationUtilities.CreateTypeDescription(lambdaResultType, enabledNullable),
+			SourceType: lambdaParamType.CreateTypeDescription(enabledNullable),
+			PropertyType: lambdaResultType.CreateTypeDescription(enabledNullable),
 			Path: new EquatableArray<IPathPart>([.. pathParseResult.Value]),
 			SetterOptions: DeriveSetterOptions(lambdaBodyResult.Value, context.SemanticModel, enabledNullable),
 			NullableContextEnabled: enabledNullable,
@@ -325,8 +331,8 @@ static bool IsWritable(ISymbol? symbol)
 		static bool AcceptsNullValue(ISymbol? symbol, bool enabledNullable)
 			=> symbol switch
 			{
-				IPropertySymbol propertySymbol => BindingGenerationUtilities.IsTypeNullable(propertySymbol.Type, enabledNullable),
-				IFieldSymbol fieldSymbol => BindingGenerationUtilities.IsTypeNullable(fieldSymbol.Type, enabledNullable),
+				IPropertySymbol propertySymbol => propertySymbol.Type.IsTypeNullable(enabledNullable),
+				IFieldSymbol fieldSymbol => fieldSymbol.Type.IsTypeNullable(enabledNullable),
 				_ => false,
 			};
 	}

src/Controls/src/BindingSourceGen/ITypeSymbolExtensions.cs

@@ -0,0 +1,70 @@
+using Microsoft.CodeAnalysis;
+
+namespace Microsoft.Maui.Controls.BindingSourceGen;
+
+internal static class ITypeSymbolExtensions
+{
+	internal static bool IsTypeNullable(this ITypeSymbol typeInfo, bool enabledNullable)
+	{
+		if (!enabledNullable && typeInfo.IsReferenceType)
+		{
+			return true;
+		}
+
+		return typeInfo.IsNullableValueType() || typeInfo.IsNullableReferenceType();
+	}
+
+	internal static TypeDescription CreateTypeDescription(this ITypeSymbol typeSymbol, bool enabledNullable)
+	{
+		var isNullable = IsTypeNullable(typeSymbol, enabledNullable);
+		return new TypeDescription(
+			GlobalName: GetGlobalName(typeSymbol, isNullable, typeSymbol.IsValueType),
+			IsNullable: isNullable,
+			IsGenericParameter: typeSymbol.Kind == SymbolKind.TypeParameter, //TODO: Add support for generic parameters
+			IsValueType: typeSymbol.IsValueType);
+	}
+
+	private static bool IsNullableValueType(this ITypeSymbol typeInfo) =>
+		typeInfo is INamedTypeSymbol namedTypeSymbol
+			&& namedTypeSymbol.IsGenericType
+			&& namedTypeSymbol.ConstructedFrom.SpecialType == SpecialType.System_Nullable_T;
+
+	private static bool IsNullableReferenceType(this ITypeSymbol typeInfo) =>
+		typeInfo.IsReferenceType && typeInfo.NullableAnnotation == NullableAnnotation.Annotated;
+
+
+	private static string GetGlobalName(this ITypeSymbol typeSymbol, bool isNullable, bool isValueType)
+	{
+		if (isNullable && isValueType)
+		{
+			// Strips the "?" from the type name
+			return ((INamedTypeSymbol)typeSymbol).TypeArguments[0].ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
+		}
+
+		return typeSymbol.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
+	}
+}
+
+internal static class ISymbolExtensions
+{
+	internal static bool IsAccessible(this ISymbol symbol) =>
+		symbol.DeclaredAccessibility == Accessibility.Public
+		|| symbol.DeclaredAccessibility == Accessibility.Internal
+		|| symbol.DeclaredAccessibility == Accessibility.ProtectedOrInternal;
+
+	internal static AccessorKind ToAccessorKind(this ISymbol symbol)
+	{
+		return symbol switch
+		{
+			IFieldSymbol _ => AccessorKind.Field,
+			IPropertySymbol _ => AccessorKind.Property,
+			_ => throw new ArgumentException("Symbol is not a field or property.", nameof(symbol))
+		};
+	}
+}
+
+public enum AccessorKind
+{
+	Field,
+	Property,
+}