Expression trees: optional arguments

Author: cston

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -4062,6 +4062,7 @@ You should consider suppressing the warning only if you're sure that you don't w
     <value>Named argument '{0}' is used out-of-position but is followed by an unnamed argument</value>
   </data>
   <data name="ERR_DefaultValueUsedWithAttributes" xml:space="preserve">
+    <!-- PROTOTYPE: Should be "DefaultParameterValueAttribute". -->
     <value>Cannot specify default parameter value in conjunction with DefaultParameterAttribute or OptionalAttribute</value>
   </data>
   <data name="ERR_DefaultValueMustBeConstant" xml:space="preserve">

src/Compilers/CSharp/Portable/Lowering/DiagnosticsPass_ExpressionTrees.cs

@@ -328,14 +328,6 @@ private void VisitCall(
                 {
                     Error(ErrorCode.ERR_ExpressionTreeContainsIndexedProperty, node);
                 }
-                else if (hasDefaultArgument(arguments, defaultArguments))
-                {
-                    Error(ErrorCode.ERR_ExpressionTreeContainsOptionalArgument, node);
-                }
-                else if (!argumentNamesOpt.IsDefaultOrEmpty)
-                {
-                    Error(ErrorCode.ERR_ExpressionTreeContainsNamedArgument, node);
-                }
                 else if (IsComCallWithRefOmitted(method, arguments, argumentRefKindsOpt))
                 {
                     Error(ErrorCode.ERR_ComRefCallInExpressionTree, node);
@@ -353,19 +345,6 @@ private void VisitCall(
                     Error(ErrorCode.ERR_ExpressionTreeContainsAbstractStaticMemberAccess, node);
                 }
             }
-
-            static bool hasDefaultArgument(ImmutableArray<BoundExpression> arguments, BitVector defaultArguments)
-            {
-                for (int i = 0; i < arguments.Length; i++)
-                {
-                    if (defaultArguments[i])
-                    {
-                        return true;
-                    }
-                }
-
-                return false;
-            }
         }
 
         public override BoundNode Visit(BoundNode node)