Add IOperation feature flag to CSharp desktop TestOptions

src/Compilers/Test/Utilities/CSharp.Desktop/TestOptions.cs

@@ -14,6 +14,8 @@ public static class TestOptions
         public static readonly CSharpParseOptions Regular = new CSharpParseOptions(kind: SourceCodeKind.Regular, documentationMode: DocumentationMode.None);
         public static readonly CSharpParseOptions RegularWithDocumentationComments = new CSharpParseOptions(kind: SourceCodeKind.Regular, documentationMode: DocumentationMode.Diagnose);
 
+        public static readonly CSharpParseOptions RegularWithIOperationFeature = Regular.WithIOperationsFeature();
+
         private static readonly SmallDictionary<string, string> s_experimentalFeatures = new SmallDictionary<string, string>(); // no experimental features to enable
         public static readonly CSharpParseOptions ExperimentalParseOptions =
             new CSharpParseOptions(kind: SourceCodeKind.Regular, documentationMode: DocumentationMode.None, languageVersion: LanguageVersion.CSharp6).WithFeatures(s_experimentalFeatures);
@@ -53,5 +55,10 @@ public static CSharpParseOptions WithStrictFeature(this CSharpParseOptions optio
         {
             return options.WithFeature("strict", "true");
         }
+
+        public static CSharpParseOptions WithIOperationsFeature(this CSharpParseOptions options)
+        {
+            return options.WithFeature("IOperation", "true");
+        }
     }
 }