Suppressing inline temp refactoring on byref locals.

The feature needs to be properly implemented taking into account that variable is byref.
For now disabling this refactoring if variable happen to be byref to avoid crash as described in dotnet#8416

src/EditorFeatures/CSharpTest/CodeActions/InlineTemporary/InlineTemporaryTests.cs

@@ -5,11 +5,16 @@
 using Microsoft.CodeAnalysis.CSharp.CodeRefactorings.InlineTemporary;
 using Roslyn.Test.Utilities;
 using Xunit;
+using System.Collections.Generic;
 
 namespace Microsoft.CodeAnalysis.Editor.CSharp.UnitTests.CodeRefactorings.InlineTemporary
 {
     public class InlineTemporaryTests : AbstractCSharpCodeActionTest
     {
+        private static readonly Dictionary<string, string> s_experimentalFeatures = new Dictionary<string, string> { { "localFunctions", "true" }, { "refLocalsAndReturns", "true" } };
+        public static readonly CSharpParseOptions ExperimentalParseOptions =
+            new CSharpParseOptions(kind: SourceCodeKind.Regular, documentationMode: DocumentationMode.None, languageVersion: LanguageVersion.CSharp6).WithFeatures(s_experimentalFeatures);
+
         protected override object CreateCodeRefactoringProvider(Workspace workspace)
         {
             return new InlineTemporaryCodeRefactoringProvider();
@@ -62,6 +67,23 @@ public async Task NotOnField()
             await TestMissingAsync(@"class C { int [||]x = 42; void M() { System.Console.WriteLine(x); } }");
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsInlineTemporary)]
+        public async Task WithRefInitializer1()
+        {
+            await TestMissingAsync(@"
+class C
+{
+    ref int M()
+    {
+        int[] arr = new[] { 1, 2, 3 };
+        ref int [||]x = ref arr[2];
+        return ref x;
+    }
+}", 
+                // TODO: propagating features to the project is currently NYI
+                parseOptions: ExperimentalParseOptions);
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsInlineTemporary)]
         public async Task SingleStatement()
         {

src/Features/CSharp/Portable/CodeRefactorings/InlineTemporary/InlineTemporaryCodeRefactoringProvider.cs

@@ -69,6 +69,12 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
                 return;
             }
 
+            if (variableDeclarator.Initializer.RefKeyword.Kind() != SyntaxKind.None)
+            {
+                // TODO: inlining byref temps is NYI
+                return;
+            }
+
             if (localDeclarationStatement.ContainsDiagnostics)
             {
                 return;