Address ILLink warning in InteropServices.JavaScript

src/libraries/System.Private.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Runtime.cs

@@ -2,10 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
-using System.Diagnostics;
 
 namespace System.Runtime.InteropServices.JavaScript
 {
@@ -19,6 +20,9 @@ public static class Runtime
         // No need to lock as it is thread safe.
         private static readonly ConditionalWeakTable<Delegate, JSObject> _weakDelegateTable = new ConditionalWeakTable<Delegate, JSObject>();
 
+        private const string TaskGetResultName = "get_Result";
+        private static readonly MethodInfo _taskGetResultMethodInfo = typeof(Task<>).GetMethod(TaskGetResultName)!;
+
         // <summary>
         // Execute the provided string in the JavaScript context
         // </summary>
@@ -350,8 +354,9 @@ void Complete()
                         }
                         else
                         {
-                            result = task_type.GetMethod("get_Result")?.Invoke(task, System.Array.Empty<object>());
+                            result = GetTaskResultMethodInfo(task_type)?.Invoke(task, null);
                         }
+
                         continuationObj.Invoke("resolve", result);
                     }
                     else
@@ -371,6 +376,30 @@ void Complete()
             }
         }
 
+        /// <summary>
+        /// Gets the MethodInfo for the Task{T}.Result property getter.
+        /// </summary>
+        /// <remarks>
+        /// This ensures the returned MethodInfo is strictly for the Task{T} type, and not
+        /// a "Result" property on some other class that derives from Task or a "new Result"
+        /// property on a class that derives from Task{T}.
+        ///
+        /// The reason for this restriction is to make this use of Reflection trim-compatible,
+        /// ensuring that trimming doesn't change the application's behavior.
+        /// </remarks>
+        [UnconditionalSuppressMessage("ReflectionAnalysis", "IL2070:UnrecognizedReflectionPattern",
+            Justification = "Task<T>.Result is preserved by the ILLinker because _taskGetResultMethodInfo was initialized with it.")]
+        private static MethodInfo? GetTaskResultMethodInfo(Type taskType)
+        {
+            MethodInfo? result = taskType.GetMethod(TaskGetResultName);
+            if (result != null && result.HasSameMetadataDefinitionAs(_taskGetResultMethodInfo))
+            {
+                return result;
+            }
+
+            return null;
+        }
+
         private static string ObjectToString(object o)
         {
             return o.ToString() ?? string.Empty;