Fix

Author: tmat

src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs

@@ -2514,7 +2514,6 @@ or ErrorCode.ERR_InstanceMemberWithUnnamedExtensionsParameter
                 or ErrorCode.ERR_InitInExtension
                 or ErrorCode.ERR_ModifierOnUnnamedReceiverParameter
                 or ErrorCode.ERR_ExtensionTypeNameDisallowed
-                or ErrorCode.ERR_ExpressionTreeContainsNamedArgumentOutOfPosition
                     => false,
             };
 #pragma warning restore CS8524 // The switch expression does not handle some values of its input type (it is not exhaustive) involving an unnamed enum value.