Fix trimming analyzer missing diagnostics for method calls in field access expressions

src/tools/illink/src/ILLink.RoslynAnalyzer/TrimAnalysis/TrimAnalysisVisitor.cs

@@ -161,6 +161,11 @@ public override MultiValue VisitInstanceReference(IInstanceReferenceOperation in
 
         public override MultiValue VisitFieldReference(IFieldReferenceOperation fieldRef, StateValue state)
         {
+            // Visit the instance to ensure that method calls or other operations
+            // used as the instance are properly analyzed for diagnostics.
+            // For example: someMethod().Field should analyze someMethod().
+            Visit(fieldRef.Instance, state);
+
             var field = fieldRef.Field;
             switch (field.Name)
             {

src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/GetInterfaceDataFlow.cs

@@ -16,6 +16,7 @@ public static void Main()
         {
             GetInterface_Name.Test();
             GetInterface_Name_IgnoreCase.Test();
+            GetInterfaceMap_DataFlow.Test();
         }
 
         class GetInterface_Name
@@ -184,6 +185,50 @@ public static void Test()
             }
         }
 
+        class GetInterfaceMap_DataFlow
+        {
+            [ExpectedWarning("IL2072", nameof(Type.GetInterfaceMap))]
+            static void TestDirectCall()
+            {
+                // This should warn: @interface doesn't have the required annotations
+                var @interface = typeof(TestType).GetInterfaces()[0];
+                _ = typeof(TestType).GetInterfaceMap(@interface);
+            }
+
+            [ExpectedWarning("IL2072", nameof(Type.GetInterfaceMap))]
+            static void TestFieldAccess()
+            {
+                // This should also warn: @interface doesn't have the required annotations
+                // even though we're accessing a field on the return value.
+                // Regression test for https://github.com/dotnet/runtime/issues/117849
+                var @interface = typeof(TestType).GetInterfaces()[0];
+                _ = typeof(TestType).GetInterfaceMap(@interface).TargetMethods;
+            }
+
+            [ExpectedWarning("IL2072", nameof(Type.GetInterfaceMap))]
+            static void TestMultipleFieldAccess()
+            {
+                // Should warn even with multiple field/property accesses
+                var @interface = typeof(TestType).GetInterfaces()[0];
+                _ = typeof(TestType).GetInterfaceMap(@interface).TargetMethods.Length;
+            }
+
+            static void TestWithAnnotation([DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicMethods | DynamicallyAccessedMemberTypes.NonPublicMethods)] Type interfaceType)
+            {
+                // This should not warn: interfaceType has the required annotations
+                _ = typeof(TestType).GetInterfaceMap(interfaceType);
+                _ = typeof(TestType).GetInterfaceMap(interfaceType).TargetMethods;
+            }
+
+            public static void Test()
+            {
+                TestDirectCall();
+                TestFieldAccess();
+                TestMultipleFieldAccess();
+                TestWithAnnotation(null);
+            }
+        }
+
         interface ITestInterface
         {
         }