From 314da0c0b6b7f0f2df1b4720a3a332eb724c295a Mon Sep 17 00:00:00 2001
From: Manodasan Wignarajah <mawign@microsoft.com>
Date: Sat, 7 Sep 2024 10:56:50 -0700
Subject: [PATCH] Detect when property expressions are used.

---
 src/Authoring/WinRT.SourceGenerator/AotOptimizer.cs |  9 +++++++++
 .../WinRT.SourceGenerator/WinRTAotCodeFixer.cs      | 13 +++++++++++++
 src/Tests/FunctionalTests/Collections/Program.cs    | 13 +++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/src/Authoring/WinRT.SourceGenerator/AotOptimizer.cs b/src/Authoring/WinRT.SourceGenerator/AotOptimizer.cs
index 1888f7eb5..0b473f14d 100644
--- a/src/Authoring/WinRT.SourceGenerator/AotOptimizer.cs
+++ b/src/Authoring/WinRT.SourceGenerator/AotOptimizer.cs
@@ -1136,6 +1136,15 @@ private static EquatableArray<VtableAttribute> GetVtableAttributesToAddOnLookupT
                         AddVtableAttributesForType(instantiatedType, namedType);
                     }
                 }
+                else if (propertyDeclaration.ExpressionBody != null)
+                {
+                    var leftSymbol = context.SemanticModel.GetSymbolInfo(propertyDeclaration.Type).Symbol;
+                    if (leftSymbol is INamedTypeSymbol namedType)
+                    {
+                        var instantiatedType = context.SemanticModel.GetTypeInfo(propertyDeclaration.ExpressionBody.Expression);
+                        AddVtableAttributesForType(instantiatedType, namedType);
+                    }
+                }
             }
             // Detect scenarios where the method or property being returned from is doing a box or cast of the type
             // in the return statement.
diff --git a/src/Authoring/WinRT.SourceGenerator/WinRTAotCodeFixer.cs b/src/Authoring/WinRT.SourceGenerator/WinRTAotCodeFixer.cs
index 5568b2aab..c06f6c167 100644
--- a/src/Authoring/WinRT.SourceGenerator/WinRTAotCodeFixer.cs
+++ b/src/Authoring/WinRT.SourceGenerator/WinRTAotCodeFixer.cs
@@ -232,6 +232,19 @@ public override void Initialize(AnalysisContext context)
                                     }
                                 }
                             }
+                            else if (propertyDeclaration.ExpressionBody != null)
+                            {
+                                var leftSymbol = context.SemanticModel.GetSymbolInfo(propertyDeclaration.Type).Symbol;
+                                if (leftSymbol is INamedTypeSymbol namedType)
+                                {
+                                    var instantiatedType = context.SemanticModel.GetTypeInfo(propertyDeclaration.ExpressionBody.Expression);
+                                    if (IsTypeOnLookupTable(instantiatedType, namedType, out var implementsOnlyCustomMappedInterface))
+                                    {
+                                        ReportEnableUnsafeDiagnostic(context.ReportDiagnostic, instantiatedType.Type, propertyDeclaration.GetLocation(), !implementsOnlyCustomMappedInterface);
+                                        return;
+                                    }
+                                }
+                            }
                         }
                         // Detect scenarios where the method or property being returned from is doing a box or cast of the type
                         // in the return statement.
diff --git a/src/Tests/FunctionalTests/Collections/Program.cs b/src/Tests/FunctionalTests/Collections/Program.cs
index 9f60c7800..ad8c5e73b 100644
--- a/src/Tests/FunctionalTests/Collections/Program.cs
+++ b/src/Tests/FunctionalTests/Collections/Program.cs
@@ -125,6 +125,9 @@
     return 101;
 }
 
+instance.BindableIterableProperty = CustomClass.DictionaryInstance;
+instance.BindableIterableProperty = CustomClass.DictionaryInstance2;
+
 var customObservableCollection = new CustomObservableCollection();
 instance.BindableIterableProperty = customObservableCollection;
 if (customObservableCollection != instance.BindableIterableProperty)
@@ -190,6 +193,16 @@ sealed partial class CustomClass : INotifyPropertyChanged
     public event PropertyChangedEventHandler PropertyChanged;
 
     public static IReadOnlyList<CustomClass> Instances { get; } = new CustomClass[] { };
+
+    public static IReadOnlyDictionary<string, CustomClass> DictionaryInstance => new Dictionary<string, CustomClass>();
+
+    public static IReadOnlyDictionary<int, CustomClass> DictionaryInstance2
+    {
+        get
+        {
+            return new Dictionary<int, CustomClass>();
+        }
+    }
 }
 
 sealed partial class CustomObservableCollection : System.Collections.ObjectModel.ObservableCollection<CustomClass>