Warn on RUC annotated ctors invoked through new() constraint in analyzer

src/ILLink.RoslynAnalyzer/ISymbolExtensions.cs

@@ -22,6 +22,19 @@ internal static bool HasAttribute (this ISymbol symbol, string attributeName)
 			return false;
 		}
 
+		internal static bool TryGetAttribute (this ISymbol member, string attributeName, [NotNullWhen (returnValue: true)] out AttributeData? attribute)
+		{
+			attribute = null;
+			foreach (var attr in member.GetAttributes ()) {
+				if (attr.AttributeClass is { } attrClass && attrClass.HasName (attributeName)) {
+					attribute = attr;
+					return true;
+				}
+			}
+
+			return false;
+		}
+
 		internal static bool TryGetOverriddenMember (this ISymbol? symbol, [NotNullWhen (returnValue: true)] out ISymbol? overridenMember)
 		{
 			overridenMember = symbol switch {

src/ILLink.RoslynAnalyzer/RequiresAnalyzerBase.cs

@@ -263,7 +263,7 @@ private void ReportMismatchInAttributesDiagnostic (SymbolAnalysisContext symbolA
 
 		protected abstract string GetMessageFromAttribute (AttributeData requiresAttribute);
 
-		private string GetUrlFromAttribute (AttributeData? requiresAttribute)
+		public static string GetUrlFromAttribute (AttributeData? requiresAttribute)
 		{
 			var url = requiresAttribute?.NamedArguments.FirstOrDefault (na => na.Key == "Url").Value.Value?.ToString ();
 			return MessageFormat.FormatRequiresAttributeUrlArg (url);

src/ILLink.RoslynAnalyzer/RequiresUnreferencedCodeAnalyzer.cs

@@ -7,6 +7,7 @@
 using ILLink.Shared;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.Diagnostics;
+using Microsoft.CodeAnalysis.Operations;
 
 namespace ILLink.RoslynAnalyzer
 {
@@ -31,6 +32,38 @@ public sealed class RequiresUnreferencedCodeAnalyzer : RequiresAnalyzerBase
 				operationContext.Operation.Syntax.GetLocation ()));
 		};
 
+		static readonly Action<OperationAnalysisContext> s_constructorConstraint = operationContext => {
+			var invocationOperation = (IInvocationOperation) operationContext.Operation;
+			if (FindContainingSymbol (operationContext, DiagnosticTargets.All) is not ISymbol containingSymbol ||
+			containingSymbol.HasAttribute (RequiresUnreferencedCodeAttribute))
+				return;
+
+			var targetMethod = invocationOperation.TargetMethod;
+			if (!targetMethod.IsGenericMethod)
+				return;
+
+			for (int i = 0; i < targetMethod.TypeParameters.Length; i++) {
+				var typeParameter = targetMethod.TypeParameters[i];
+				var typeArgument = targetMethod.TypeArguments[i];
+				if (!typeParameter.HasConstructorConstraint)
+					continue;
+
+				var typeArgCtors = ((INamedTypeSymbol) typeArgument).InstanceConstructors;
+				foreach (var instanceCtor in typeArgCtors) {
+					if (instanceCtor.Arity > 0)
+						continue;
+
+					if (instanceCtor.TryGetAttribute (RequiresUnreferencedCodeAttribute, out var requiresUnreferencedCodeAttribute)) {
+						operationContext.ReportDiagnostic (Diagnostic.Create (s_requiresUnreferencedCodeRule,
+							operationContext.Operation.Syntax.GetLocation (),
+							containingSymbol.GetDisplayName (),
+							(string) requiresUnreferencedCodeAttribute.ConstructorArguments[0].Value!,
+							GetUrlFromAttribute (requiresUnreferencedCodeAttribute)));
+					}
+				}
+			}
+		};
+
 		public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics =>
 			ImmutableArray.Create (s_dynamicTypeInvocationRule, s_requiresUnreferencedCodeRule, s_requiresUnreferencedCodeAttributeMismatch);
 
@@ -47,8 +80,15 @@ public sealed class RequiresUnreferencedCodeAnalyzer : RequiresAnalyzerBase
 		protected override bool IsAnalyzerEnabled (AnalyzerOptions options, Compilation compilation) =>
 			options.IsMSBuildPropertyValueTrue (MSBuildPropertyOptionNames.EnableTrimAnalyzer, compilation);
 
-		private protected override ImmutableArray<(Action<OperationAnalysisContext> Action, OperationKind[] OperationKind)> ExtraOperationActions =>
-			ImmutableArray.Create ((s_dynamicTypeInvocation, new OperationKind[] { OperationKind.DynamicInvocation }));
+		private protected override ImmutableArray<(Action<OperationAnalysisContext> Action, OperationKind[] OperationKind)> ExtraOperationActions {
+			get {
+				var diagsBuilder = ImmutableArray.CreateBuilder<(Action<OperationAnalysisContext>, OperationKind[])> ();
+				diagsBuilder.Add ((s_dynamicTypeInvocation, new OperationKind[] { OperationKind.DynamicInvocation }));
+				diagsBuilder.Add ((s_constructorConstraint, new OperationKind[] { OperationKind.Invocation }));
+
+				return diagsBuilder.ToImmutable ();
+			}
+		}
 
 		protected override bool VerifyAttributeArguments (AttributeData attribute) =>
 			attribute.ConstructorArguments.Length >= 1 && attribute.ConstructorArguments[0] is { Type: { SpecialType: SpecialType.System_String } } ctorArg;

test/Mono.Linker.Tests.Cases/RequiresCapability/RequiresUnreferencedCodeCapability.cs

@@ -778,8 +778,7 @@ public NewConstrainTestType () { }
 
 			static void GenericMethod<T> () where T : new() { }
 
-			// https://github.com/mono/linker/issues/2117
-			[ExpectedWarning ("IL2026", "--NewConstrainTestType.ctor--", GlobalAnalysisOnly = true)]
+			[ExpectedWarning ("IL2026", "--NewConstrainTestType.ctor--")]
 			public static void Test ()
 			{
 				GenericMethod<NewConstrainTestType> ();