Add 'CollectionExpressionIDE0304Suppressor'

src/Authoring/WinRT.SourceGenerator/CollectionExpressions/CollectionExpressionIDE0304Suppressor.cs

@@ -0,0 +1,64 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#if ROSLYN_4_12_0_OR_GREATER
+
+using System.Collections.Immutable;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Diagnostics;
+using WinRT.SourceGenerator;
+
+#nullable enable
+
+namespace Generator;
+
+/// <summary>
+/// <para>
+/// A diagnostic suppressor to suppress collection expression warnings where needed for AOT compatibility in WinRT scenarios.
+/// </para>
+/// <para>
+/// This analyzer suppress diagnostics for cases like these:
+/// <code lang="csharp">
+/// var builder = ImmutableArray.CreateBuilder<int>();
+/// builder.Add(1);
+/// builder.AddRange(new int[] { 5, 6, 7 });
+/// ImmutableArray<int> i = builder.ToImmutable();
+/// </code>
+/// </para>
+/// </summary>
+[DiagnosticAnalyzer(LanguageNames.CSharp)]
+public sealed class CollectionExpressionIDE0304Suppressor : DiagnosticSuppressor
+{
+    /// <inheritdoc/>
+    public override ImmutableArray<SuppressionDescriptor> SupportedSuppressions { get; } = [WinRTSuppressions.CollectionExpressionIDE0304];
+
+    /// <inheritdoc/>
+    public override void ReportSuppressions(SuppressionAnalysisContext context)
+    {
+        // Skip the logic if CsWinRT is not in 'auto' mode
+        if (!GeneratorExecutionContextHelper.IsCsWinRTAotOptimizerInAutoMode(context.Options.AnalyzerConfigOptionsProvider, context.Compilation))
+        {
+            return;
+        }
+
+        foreach (Diagnostic diagnostic in context.ReportedDiagnostics)
+        {
+            // The 'IDE0304' analyzer will add the location of the invocation expression in the additional locations set
+            if (diagnostic.AdditionalLocations is not [{ } invocationLocation, ..])
+            {
+                continue;
+            }
+
+            // Check the target invocation. The only thing we care about for this warning is whether the final invocation
+            // was being assigned to a concrete type (which is supported), or to a readonly interface type (which isn't).
+            SyntaxNode? syntaxNode = invocationLocation.SourceTree?.GetRoot(context.CancellationToken).FindNode(invocationLocation.SourceSpan);
+
+            if (CollectionExpressionIDE0305Suppressor.IsInvocationAssignedToUnsupportedInterfaceType(context, syntaxNode))
+            {
+                context.ReportSuppression(Suppression.Create(WinRTSuppressions.CollectionExpressionIDE0304, diagnostic));
+            }
+        }
+    }
+}
+
+#endif

src/Authoring/WinRT.SourceGenerator/CollectionExpressions/CollectionExpressionIDE0305Suppressor.cs

@@ -8,6 +8,7 @@
 using Microsoft.CodeAnalysis.Diagnostics;
 using Microsoft.CodeAnalysis.CSharp;
 using WinRT.SourceGenerator;
+using System.Diagnostics.CodeAnalysis;
 
 #nullable enable
 
@@ -57,6 +58,14 @@ public static bool IsInvocationAssignedToUnsupportedInterfaceType(SuppressionAna
         // Try to get the syntax node matching the location of the diagnostic
         SyntaxNode? syntaxNode = diagnostic.Location.SourceTree?.GetRoot(context.CancellationToken).FindNode(diagnostic.Location.SourceSpan);
 
+        return IsInvocationAssignedToUnsupportedInterfaceType(context, syntaxNode);
+    }
+
+    /// <summary>
+    /// Checks whether a given invocation is assigning to an unsupported interface type.
+    /// </summary>
+    public static bool IsInvocationAssignedToUnsupportedInterfaceType(SuppressionAnalysisContext context, [NotNullWhen(true)] SyntaxNode? syntaxNode)
+    {
         // We expect to have found an invocation expression (eg. 'ToList()')
         if (syntaxNode?.Kind() is not SyntaxKind.InvocationExpression)
         {

src/Authoring/WinRT.SourceGenerator/WinRT.SourceGenerator.projitems

@@ -17,6 +17,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)CollectionExpressions\CollectionExpressionAnalyzer.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CollectionExpressions\CollectionExpressionIDE0300Suppressor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CollectionExpressions\CollectionExpressionIDE0303Suppressor.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)CollectionExpressions\CollectionExpressionIDE0304Suppressor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CollectionExpressions\CollectionExpressionIDE0305Suppressor.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)CsWinRTDiagnosticStrings.Designer.cs">
       <DependentUpon>CsWinRTDiagnosticStrings.resx</DependentUpon>