Merge pull request #19674 from genlu/arglistFix

Fix crash when creating IArgument for `__arglist` argument

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_Call.cs

@@ -515,12 +515,31 @@ private static bool IsSafeForReordering(BoundExpression expression, RefKind kind
             //
             // If neither of those are the case then we can just take an early out.
 
-
-            if (CanSkipRewriting(arguments, methodOrIndexer, expanded, argsToParamsOpt, invokedAsExtensionMethod, out var isComReceiver))
-            {                                                                                  
+            if (CanSkipRewriting(arguments, methodOrIndexer, expanded, argsToParamsOpt, invokedAsExtensionMethod, out var _))
+            {
                 // In this case, the invocation is not in expanded form and there's no named argument provided.
                 // So we just return list of arguments as is.
-                return arguments.ZipAsArray(methodOrIndexer.GetParameters(), (a, p) => BoundCall.CreateArgumentOperation(ArgumentKind.Explicit, p, a));
+
+                ImmutableArray<ParameterSymbol> parameters = methodOrIndexer.GetParameters();
+                ArrayBuilder<IArgument> argumentsBuilder = ArrayBuilder<IArgument>.GetInstance(arguments.Length);
+
+                int i = 0;
+                for (; i < parameters.Length; ++i)
+                {
+                    argumentsBuilder.Add(BoundCall.CreateArgumentOperation(ArgumentKind.Explicit, parameters[i], arguments[i]));
+                }
+
+                // TODO: In case of __arglist, we will have more arguments than parameters, 
+                //       set the parameter to null for __arglist argument for now.
+                //       https://github.com/dotnet/roslyn/issues/19673
+                for (; i < arguments.Length; ++i)
+                {
+                    argumentsBuilder.Add(BoundCall.CreateArgumentOperation(ArgumentKind.Explicit, null, arguments[i]));
+                }
+
+                Debug.Assert(methodOrIndexer.GetIsVararg() ^ parameters.Length == arguments.Length);
+
+                return argumentsBuilder.ToImmutableAndFree();
             }                                                                                                                   
 
             return BuildArgumentsInEvaluationOrder(syntax, 
@@ -558,7 +577,7 @@ private static bool IsSafeForReordering(BoundExpression expression, RefKind kind
                                     ((MethodSymbol)methodOrIndexer).Parameters[0].Type as NamedTypeSymbol :
                                     methodOrIndexer.ContainingType;
 
-            isComReceiver = (object)receiverNamedType != null && receiverNamedType.IsComImport; 
+            isComReceiver = (object)receiverNamedType != null && receiverNamedType.IsComImport;
 
             return rewrittenArguments.Length == methodOrIndexer.GetParameterCount() &&
                 argsToParamsOpt.IsDefault &&

src/Compilers/CSharp/Test/Semantic/IOperation/IOperationTests_IArgument.cs

@@ -990,6 +990,45 @@ void M2(string x )
             VerifyOperationTreeAndDiagnosticsForTest<InvocationExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
         }
 
+        [Fact]
+        public void VarArgsCall()
+        {
+            string source = @"
+using System;
+
+public class P
+{
+    void M()
+    {
+        /*<bind>*/Console.Write(""{0} {1} {2} {3} {4}"", 1, 2, 3, 4, __arglist(5))/*</bind>*/;
+    }
+}
+";
+            string expectedOperationTree = @"
+IInvocationExpression (static void System.Console.Write(System.String format, System.Object arg0, System.Object arg1, System.Object arg2, System.Object arg3, __arglist)) (OperationKind.InvocationExpression, Type: System.Void) (Syntax: 'Console.Wri ... arglist(5))')
+  Arguments(6): IArgument (ArgumentKind.Explicit, Matching Parameter: format) (OperationKind.Argument) (Syntax: '""{0} {1} {2} {3} {4}""')
+      ILiteralExpression (OperationKind.LiteralExpression, Type: System.String, Constant: ""{0} {1} {2} {3} {4}"") (Syntax: '""{0} {1} {2} {3} {4}""')
+    IArgument (ArgumentKind.Explicit, Matching Parameter: arg0) (OperationKind.Argument) (Syntax: '1')
+      IConversionExpression (ConversionKind.Cast, Implicit) (OperationKind.ConversionExpression, Type: System.Object) (Syntax: '1')
+        ILiteralExpression (Text: 1) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 1) (Syntax: '1')
+    IArgument (ArgumentKind.Explicit, Matching Parameter: arg1) (OperationKind.Argument) (Syntax: '2')
+      IConversionExpression (ConversionKind.Cast, Implicit) (OperationKind.ConversionExpression, Type: System.Object) (Syntax: '2')
+        ILiteralExpression (Text: 2) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 2) (Syntax: '2')
+    IArgument (ArgumentKind.Explicit, Matching Parameter: arg2) (OperationKind.Argument) (Syntax: '3')
+      IConversionExpression (ConversionKind.Cast, Implicit) (OperationKind.ConversionExpression, Type: System.Object) (Syntax: '3')
+        ILiteralExpression (Text: 3) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 3) (Syntax: '3')
+    IArgument (ArgumentKind.Explicit, Matching Parameter: arg3) (OperationKind.Argument) (Syntax: '4')
+      IConversionExpression (ConversionKind.Cast, Implicit) (OperationKind.ConversionExpression, Type: System.Object) (Syntax: '4')
+        ILiteralExpression (Text: 4) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 4) (Syntax: '4')
+    IArgument (ArgumentKind.Explicit, Matching Parameter: null) (OperationKind.Argument, IsInvalid) (Syntax: '__arglist(5)')
+      IOperation:  (OperationKind.None) (Syntax: '__arglist(5)')
+        Children(1): ILiteralExpression (Text: 5) (OperationKind.LiteralExpression, Type: System.Int32, Constant: 5) (Syntax: '5')
+";
+            var expectedDiagnostics = DiagnosticDescription.None;
+
+            VerifyOperationTreeAndDiagnosticsForTest<InvocationExpressionSyntax>(source, expectedOperationTree, expectedDiagnostics);
+        }
+
         [Fact]
         public void InvalidConversionForDefaultArgument_InSource()
         {