Expression trees: support optional arguments and named arguments in parameter order

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -4172,6 +4172,9 @@ You should consider suppressing the warning only if you're sure that you don't w
   <data name="ERR_ExpressionTreeContainsNamedArgument" xml:space="preserve">
     <value>An expression tree may not contain a named argument specification</value>
   </data>
+  <data name="ERR_ExpressionTreeContainsNamedArgumentOutOfPosition" xml:space="preserve">
+    <value>An expression tree may not contain a named argument specification out of position</value>
+  </data>
   <data name="ERR_ExpressionTreeContainsOptionalArgument" xml:space="preserve">
     <value>An expression tree may not contain a call or invocation that uses optional arguments</value>
   </data>

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

@@ -2397,6 +2397,7 @@ internal enum ErrorCode
         ERR_InitInExtension = 9304,
         ERR_ModifierOnUnnamedReceiverParameter = 9305,
         ERR_ExtensionTypeNameDisallowed = 9306,
+        ERR_ExpressionTreeContainsNamedArgumentOutOfPosition = 9307,
 
         // Note: you will need to do the following after adding errors:
         //  1) Update ErrorFacts.IsBuildOnlyDiagnostic (src/Compilers/CSharp/Portable/Errors/ErrorFacts.cs)

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

@@ -2513,6 +2513,7 @@ 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.

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

@@ -301,6 +301,7 @@ internal enum MessageID
         IDS_FeaturePartialEventsAndConstructors = MessageBase + 12852,
         IDS_FeatureExtensions = MessageBase + 12853,
         IDS_FeatureNullConditionalAssignment = MessageBase + 12854,
+        IDS_FeatureExpressionOptionalAndNamedArguments = MessageBase + 12855,
     }
 
     // Message IDs may refer to strings that need to be localized.
@@ -488,6 +489,7 @@ internal static LanguageVersion RequiredVersion(this MessageID feature)
                 case MessageID.IDS_FeaturePartialEventsAndConstructors:
                 case MessageID.IDS_FeatureExtensions:
                 case MessageID.IDS_FeatureNullConditionalAssignment:
+                case MessageID.IDS_FeatureExpressionOptionalAndNamedArguments:
                     return LanguageVersion.Preview;
 
                 // C# 13.0 features.

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

@@ -307,6 +307,7 @@ private void VisitCall(
             ImmutableArray<BoundExpression> arguments,
             ImmutableArray<RefKind> argumentRefKindsOpt,
             ImmutableArray<string> argumentNamesOpt,
+            ImmutableArray<int> argsToParamsOpt,
             BitVector defaultArguments,
             BoundNode node)
         {
@@ -328,14 +329,22 @@ private void VisitCall(
                 {
                     Error(ErrorCode.ERR_ExpressionTreeContainsIndexedProperty, node);
                 }
-                else if (hasDefaultArgument(arguments, defaultArguments))
+                else if (hasDefaultArgument(arguments, defaultArguments) &&
+                    !_compilation.IsFeatureEnabled(MessageID.IDS_FeatureExpressionOptionalAndNamedArguments))
                 {
                     Error(ErrorCode.ERR_ExpressionTreeContainsOptionalArgument, node);
                 }
-                else if (!argumentNamesOpt.IsDefaultOrEmpty)
+                else if (!argumentNamesOpt.IsDefaultOrEmpty &&
+                    !_compilation.IsFeatureEnabled(MessageID.IDS_FeatureExpressionOptionalAndNamedArguments))
                 {
                     Error(ErrorCode.ERR_ExpressionTreeContainsNamedArgument, node);
                 }
+                else if (!argumentNamesOpt.IsDefaultOrEmpty &&
+                    hasNamedArgumentOutOfOrder(argsToParamsOpt))
+                {
+                    Debug.Assert(_compilation.IsFeatureEnabled(MessageID.IDS_FeatureExpressionOptionalAndNamedArguments));
+                    Error(ErrorCode.ERR_ExpressionTreeContainsNamedArgumentOutOfPosition, node);
+                }
                 else if (IsComCallWithRefOmitted(method, arguments, argumentRefKindsOpt))
                 {
                     Error(ErrorCode.ERR_ComRefCallInExpressionTree, node);
@@ -366,6 +375,22 @@ static bool hasDefaultArgument(ImmutableArray<BoundExpression> arguments, BitVec
 
                 return false;
             }
+
+            static bool hasNamedArgumentOutOfOrder(ImmutableArray<int> argsToParamsOpt)
+            {
+                if (argsToParamsOpt.IsDefaultOrEmpty)
+                {
+                    return false;
+                }
+                for (int i = 0; i < argsToParamsOpt.Length; i++)
+                {
+                    if (argsToParamsOpt[i] != i)
+                    {
+                        return true;
+                    }
+                }
+                return false;
+            }
         }
 
         public override BoundNode Visit(BoundNode node)
@@ -474,7 +499,7 @@ public override BoundNode VisitCall(BoundCall node)
 
                 do
                 {
-                    VisitCall(node.Method, null, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.DefaultArguments, node);
+                    visitCall(node);
                     CheckReferenceToMethodIfLocalFunction(node, node.Method);
                     this.VisitList(node.Arguments);
                 }
@@ -484,14 +509,19 @@ public override BoundNode VisitCall(BoundCall node)
             }
             else
             {
-                VisitCall(node.Method, null, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.DefaultArguments, node);
+                visitCall(node);
                 CheckReceiverIfField(node.ReceiverOpt);
                 CheckReferenceToMethodIfLocalFunction(node, node.Method);
                 this.Visit(node.ReceiverOpt);
                 this.VisitList(node.Arguments);
             }
 
             return null;
+
+            void visitCall(BoundCall node)
+            {
+                VisitCall(node.Method, null, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.ArgsToParamsOpt, node.DefaultArguments, node);
+            }
         }
 
         /// <summary>
@@ -520,13 +550,13 @@ public override BoundNode VisitCollectionElementInitializer(BoundCollectionEleme
                 Error(ErrorCode.ERR_ExtensionCollectionElementInitializerInExpressionTree, node);
             }
 
-            VisitCall(node.AddMethod, null, node.Arguments, default(ImmutableArray<RefKind>), default(ImmutableArray<string>), node.DefaultArguments, node);
+            VisitCall(node.AddMethod, null, node.Arguments, default(ImmutableArray<RefKind>), default(ImmutableArray<string>), default(ImmutableArray<int>), node.DefaultArguments, node);
             return base.VisitCollectionElementInitializer(node);
         }
 
         public override BoundNode VisitObjectCreationExpression(BoundObjectCreationExpression node)
         {
-            VisitCall(node.Constructor, null, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.DefaultArguments, node);
+            VisitCall(node.Constructor, null, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.ArgsToParamsOpt, node.DefaultArguments, node);
             return base.VisitObjectCreationExpression(node);
         }
 
@@ -536,7 +566,7 @@ public override BoundNode VisitIndexerAccess(BoundIndexerAccess node)
             var method = indexer.GetOwnOrInheritedGetMethod() ?? indexer.GetOwnOrInheritedSetMethod();
             if ((object)method != null)
             {
-                VisitCall(method, indexer, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.DefaultArguments, node);
+                VisitCall(method, indexer, node.Arguments, node.ArgumentRefKindsOpt, node.ArgumentNamesOpt, node.ArgsToParamsOpt, node.DefaultArguments, node);
             }
             CheckReceiverIfField(node.ReceiverOpt);
             return base.VisitIndexerAccess(node);