Special casing for single line ternary expressions that without singleline comments in C#

src/EditorFeatures/CSharpTest/Diagnostics/Async/AddAwaitTests.cs

@@ -90,7 +90,7 @@ async Task<int> Test2()
         }
 
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
-        public void BadAsyncReturnOperand_WithTrailingTrivia1()
+        public void BadAsyncReturnOperand_ConditionalExpressionWithTrailingTrivia_SingleLine()
         {
             var initial =
 @"using System.Threading.Tasks;
@@ -114,14 +114,14 @@ class Program
 
     async Task<int> Test2()
     {
-        return await (true ? Test() /* true */ : Test()) /* false */;
+        return await (true ? Test() /* true */ : Test() /* false */);
     }
 }";
             Test(initial, expected, compareTokens: false);
         }
 
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
-        public void BadAsyncReturnOperand_WithTrailingTrivia2()
+        public void BadAsyncReturnOperand_ConditionalExpressionWithTrailingTrivia_Multiline()
         {
             var initial =
 @"using System.Threading.Tasks;
@@ -155,6 +155,136 @@ async Task<int> Test2()
             Test(initial, expected, compareTokens: false);
         }
 
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
+        public void BadAsyncReturnOperand_NullCoalescingExpressionWithTrailingTrivia_SingleLine()
+        {
+            var initial =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {[|
+        return null /* 0 */ ?? Test() /* 1 */;
+    |]}
+}";
+
+            var expected =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {
+        return await (null /* 0 */ ?? Test() /* 1 */);
+    }
+}";
+            Test(initial, expected, compareTokens: false);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
+        public void BadAsyncReturnOperand_NullCoalescingExpressionWithTrailingTrivia_Multiline()
+        {
+            var initial =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {[|
+        return null   // aaa
+            ?? Test() // bbb
+            ;
+    |]}
+}";
+
+            var expected =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {
+        return await (null   // aaa
+            ?? Test()) // bbb
+            ;
+    }
+}";
+            Test(initial, expected, compareTokens: false);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
+        public void BadAsyncReturnOperand_AsExpressionWithTrailingTrivia_SingleLine()
+        {
+            var initial =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test2()
+    {[|
+        return null /* 0 */ as Task<int> /* 1 */;
+    |]}
+}";
+
+            var expected =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {
+        return await (null /* 0 */ as Task<int> /* 1 */);
+    }
+}";
+            Test(initial, expected, compareTokens: false);
+        }
+
+        [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
+        public void BadAsyncReturnOperand_AsExpressionWithTrailingTrivia_Multiline()
+        {
+            var initial =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {[|
+        return null      // aaa
+            as Task<int> // bbb
+            ;
+    |]}
+}";
+
+            var expected =
+@"using System.Threading.Tasks;
+
+class Program
+{
+    async Task<int> Test() => 3;
+
+    async Task<int> Test2()
+    {
+        return await (null      // aaa
+            as Task<int>) // bbb
+            ;
+    }
+}";
+            Test(initial, expected, compareTokens: false);
+        }
+
         [Fact, Trait(Traits.Feature, Traits.Features.CodeActionsAddAwait)]
         public void TaskNotAwaited()
         {

src/Features/CSharp/Portable/CodeFixes/Async/CSharpAddAwaitCodeFixProvider.cs

@@ -148,6 +148,17 @@ private static bool IsInAsyncFunction(ExpressionSyntax expression)
 
         private static SyntaxNode ConvertToAwaitExpression(ExpressionSyntax expression)
         {
+            if ((expression is BinaryExpressionSyntax || expression is ConditionalExpressionSyntax) && expression.HasTrailingTrivia)
+            {
+                var expWithTrailing = expression.WithoutLeadingTrivia();
+                var span = expWithTrailing.GetLocation().GetLineSpan().Span;
+                if (span.Start.Line == span.End.Line && !expWithTrailing.DescendantTrivia().Any(trivia => trivia.IsKind(SyntaxKind.SingleLineCommentTrivia)))
+                {
+                    return SyntaxFactory.AwaitExpression(SyntaxFactory.ParenthesizedExpression(expWithTrailing))
+                                        .WithLeadingTrivia(expression.GetLeadingTrivia())
+                                        .WithAdditionalAnnotations(Formatter.Annotation, Simplifier.Annotation);
+                }
+            }
             return SyntaxFactory.AwaitExpression(expression.WithoutTrivia().Parenthesize())
                                 .WithTriviaFrom(expression)
                                 .WithAdditionalAnnotations(Formatter.Annotation, Simplifier.Annotation);