Avoid stack overflow due to deep recursion on long chain of calls.

src/Compilers/CSharp/Portable/Binder/Binder_Invocation.cs

@@ -175,17 +175,67 @@ private BoundExpression BindInvocationExpression(
                 BindArgumentsAndNames(node.ArgumentList, diagnostics, analyzedArguments, allowArglist: false);
                 result = BindArgListOperator(node, diagnostics, analyzedArguments);
             }
+            else if (receiverIsInvocation(node, out InvocationExpressionSyntax nested))
+            {
+                var invocations = ArrayBuilder<InvocationExpressionSyntax>.GetInstance();
+
+                invocations.Push(node);
+                node = nested;
+                while (receiverIsInvocation(node, out nested))
+                {
+                    invocations.Push(node);
+                    node = nested;
+                }
+
+                BoundExpression boundExpression = BindMethodGroup(node.Expression, invoked: true, indexed: false, diagnostics: diagnostics);
+
+                while (true)
+                {
+                    result = bindArgumentsAndInvocation(node, boundExpression, analyzedArguments, diagnostics);
+                    nested = node;
+
+                    if (!invocations.TryPop(out node))
+                    {
+                        break;
+                    }
+
+                    Debug.Assert(node.Expression.Kind() is SyntaxKind.SimpleMemberAccessExpression);
+                    var memberAccess = (MemberAccessExpressionSyntax)node.Expression;
+                    analyzedArguments.Clear();
+                    VerifyUnchecked(nested, diagnostics, result); // BindExpression does this after calling BindExpressionInternal  
+                    boundExpression = BindMemberAccessWithBoundLeft(memberAccess, result, memberAccess.Name, memberAccess.OperatorToken, invoked: true, indexed: false, diagnostics);
+                }
+
+                invocations.Free();
+            }
             else
             {
                 BoundExpression boundExpression = BindMethodGroup(node.Expression, invoked: true, indexed: false, diagnostics: diagnostics);
+                result = bindArgumentsAndInvocation(node, boundExpression, analyzedArguments, diagnostics);
+            }
+
+            analyzedArguments.Free();
+            return result;
+
+            BoundExpression bindArgumentsAndInvocation(InvocationExpressionSyntax node, BoundExpression boundExpression, AnalyzedArguments analyzedArguments, BindingDiagnosticBag diagnostics)
+            {
                 boundExpression = CheckValue(boundExpression, BindValueKind.RValueOrMethodGroup, diagnostics);
                 string name = boundExpression.Kind == BoundKind.MethodGroup ? GetName(node.Expression) : null;
                 BindArgumentsAndNames(node.ArgumentList, diagnostics, analyzedArguments, allowArglist: true);
-                result = BindInvocationExpression(node, node.Expression, name, boundExpression, analyzedArguments, diagnostics);
+                return BindInvocationExpression(node, node.Expression, name, boundExpression, analyzedArguments, diagnostics);
             }
 
-            analyzedArguments.Free();
-            return result;
+            static bool receiverIsInvocation(InvocationExpressionSyntax node, out InvocationExpressionSyntax nested)
+            {
+                if (node.Expression is MemberAccessExpressionSyntax { Expression: InvocationExpressionSyntax receiver, RawKind: (int)SyntaxKind.SimpleMemberAccessExpression } && !receiver.MayBeNameofOperator())
+                {
+                    nested = receiver;
+                    return true;
+                }
+
+                nested = null;
+                return false;
+            }
         }
 
         private BoundExpression BindArgListOperator(InvocationExpressionSyntax node, BindingDiagnosticBag diagnostics, AnalyzedArguments analyzedArguments)

src/Compilers/CSharp/Portable/Binder/ExpressionVariableFinder.cs

@@ -65,15 +65,6 @@ protected void FindExpressionVariables(
             _variablesBuilder = save;
         }
 
-        public override void Visit(SyntaxNode node)
-        {
-            if (node != null)
-            {
-                // no stackguard
-                ((CSharpSyntaxNode)node).Accept(this);
-            }
-        }
-
         public override void VisitSwitchExpression(SwitchExpressionSyntax node)
         {
             Visit(node.GoverningExpression);
@@ -348,6 +339,50 @@ public override void VisitBinaryExpression(BinaryExpressionSyntax node)
             operands.Free();
         }
 
+        public override void VisitInvocationExpression(InvocationExpressionSyntax node)
+        {
+            if (receiverIsInvocation(node, out InvocationExpressionSyntax nested))
+            {
+                var invocations = ArrayBuilder<InvocationExpressionSyntax>.GetInstance();
+
+                invocations.Push(node);
+
+                node = nested;
+                while (receiverIsInvocation(node, out nested))
+                {
+                    invocations.Push(node);
+                    node = nested;
+                }
+
+                Visit(node.Expression);
+
+                do
+                {
+                    Visit(node.ArgumentList);
+                }
+                while (invocations.TryPop(out node));
+
+                invocations.Free();
+            }
+            else
+            {
+                Visit(node.Expression);
+                Visit(node.ArgumentList);
+            }
+
+            static bool receiverIsInvocation(InvocationExpressionSyntax node, out InvocationExpressionSyntax nested)
+            {
+                if (node.Expression is MemberAccessExpressionSyntax { Expression: InvocationExpressionSyntax receiver })
+                {
+                    nested = receiver;
+                    return true;
+                }
+
+                nested = null;
+                return false;
+            }
+        }
+
         public override void VisitDeclarationExpression(DeclarationExpressionSyntax node)
         {
             var argumentSyntax = node.Parent as ArgumentSyntax;

src/Compilers/CSharp/Portable/Binder/LocalBinderFactory.cs

@@ -12,6 +12,7 @@
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using ReferenceEqualityComparer = Roslyn.Utilities.ReferenceEqualityComparer;
 
 namespace Microsoft.CodeAnalysis.CSharp
@@ -240,9 +241,49 @@ public override void VisitInvocationExpression(InvocationExpressionSyntax node)
                 return;
             }
 
-            base.VisitInvocationExpression(node);
+            if (receiverIsInvocation(node, out InvocationExpressionSyntax? nested))
+            {
+                var invocations = ArrayBuilder<InvocationExpressionSyntax>.GetInstance();
+
+                invocations.Push(node);
+
+                node = nested;
+                while (receiverIsInvocation(node, out nested))
+                {
+                    invocations.Push(node);
+                    node = nested;
+                }
+
+                Visit(node.Expression);
+
+                do
+                {
+                    Visit(node.ArgumentList);
+                }
+                while (invocations.TryPop(out node!));
+
+                invocations.Free();
+            }
+            else
+            {
+                Visit(node.Expression);
+                Visit(node.ArgumentList);
+            }
+
             return;
 
+            static bool receiverIsInvocation(InvocationExpressionSyntax node, [NotNullWhen(true)] out InvocationExpressionSyntax? nested)
+            {
+                if (node.Expression is MemberAccessExpressionSyntax { Expression: InvocationExpressionSyntax receiver } && !receiver.MayBeNameofOperator())
+                {
+                    nested = receiver;
+                    return true;
+                }
+
+                nested = null;
+                return false;
+            }
+
             static Symbol getAttributeTarget(Binder current)
             {
                 Debug.Assert((current.Flags & BinderFlags.InContextualAttributeBinder) != 0);

src/Compilers/CSharp/Portable/Binder/RefSafetyAnalysis.cs

@@ -647,8 +647,6 @@ private void SetPatternLocalScopes(BoundObjectPattern pattern)
 
         private void VisitArgumentsAndGetArgumentPlaceholders(BoundExpression? receiverOpt, ImmutableArray<BoundExpression> arguments)
         {
-            Visit(receiverOpt);
-
             for (int i = 0; i < arguments.Length; i++)
             {
                 var arg = arguments[i];
@@ -663,7 +661,7 @@ private void VisitArgumentsAndGetArgumentPlaceholders(BoundExpression? receiverO
             }
         }
 
-        public override BoundNode? VisitCall(BoundCall node)
+        protected override void VisitArguments(BoundCall node)
         {
             VisitArgumentsAndGetArgumentPlaceholders(node.ReceiverOpt, node.Arguments);
 
@@ -682,7 +680,12 @@ private void VisitArgumentsAndGetArgumentPlaceholders(BoundExpression? receiverO
                     _diagnostics);
             }
 
-            return null;
+#if DEBUG
+            if (_visited is { } && _visited.Count <= MaxTrackVisited)
+            {
+                _visited.Add(node);
+            }
+#endif
         }
 
         private void GetInterpolatedStringPlaceholders(
@@ -786,6 +789,7 @@ private void VisitObjectCreationExpressionBase(BoundObjectCreationExpressionBase
 
         public override BoundNode? VisitIndexerAccess(BoundIndexerAccess node)
         {
+            Visit(node.ReceiverOpt);
             VisitArgumentsAndGetArgumentPlaceholders(node.ReceiverOpt, node.Arguments);
 
             if (!node.HasErrors)

src/Compilers/CSharp/Portable/BoundTree/BoundTreeWalker.cs

@@ -135,5 +135,52 @@ protected BoundTreeWalkerWithStackGuardWithoutRecursionOnTheLeftOfBinaryOperator
             rightOperands.Free();
             return null;
         }
+
+        public sealed override BoundNode? VisitCall(BoundCall node)
+        {
+            if (node.ReceiverOpt is BoundCall receiver1)
+            {
+                var calls = ArrayBuilder<BoundCall>.GetInstance();
+
+                calls.Push(node);
+
+                node = receiver1;
+                while (node.ReceiverOpt is BoundCall receiver2)
+                {
+                    calls.Push(node);
+                    node = receiver2;
+                }
+
+                VisitReceiver(node);
+
+                do
+                {
+                    VisitArguments(node);
+                }
+                while (calls.TryPop(out node!));
+
+                calls.Free();
+            }
+            else
+            {
+                VisitReceiver(node);
+                VisitArguments(node);
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        /// Called only for the first (in evaluation order) <see cref="BoundCall"/> in the chain.
+        /// </summary>
+        protected virtual void VisitReceiver(BoundCall node)
+        {
+            this.Visit(node.ReceiverOpt);
+        }
+
+        protected virtual void VisitArguments(BoundCall node)
+        {
+            this.VisitList(node.Arguments);
+        }
     }
 }

src/Compilers/CSharp/Portable/CodeGen/EmitAddress.cs

@@ -111,10 +111,8 @@ private LocalDefinition EmitAddress(BoundExpression expression, AddressKind addr
 
                 case BoundKind.Call:
                     var call = (BoundCall)expression;
-                    var methodRefKind = call.Method.RefKind;
 
-                    if (methodRefKind == RefKind.Ref ||
-                        (IsAnyReadOnly(addressKind) && methodRefKind == RefKind.RefReadOnly))
+                    if (UseCallResultAsAddress(call, addressKind))
                     {
                         EmitCallExpression(call, UseKind.UsedAsAddress);
                         break;
@@ -178,6 +176,13 @@ private LocalDefinition EmitAddress(BoundExpression expression, AddressKind addr
             return null;
         }
 
+        private static bool UseCallResultAsAddress(BoundCall call, AddressKind addressKind)
+        {
+            var methodRefKind = call.Method.RefKind;
+            return methodRefKind == RefKind.Ref ||
+                   (IsAnyReadOnly(addressKind) && methodRefKind == RefKind.RefReadOnly);
+        }
+
         private LocalDefinition EmitPassByCopyAddress(BoundPassByCopy passByCopyExpr, AddressKind addressKind)
         {
             // Normally we can just defer PassByCopy to the `default`,
@@ -505,7 +510,7 @@ private LocalDefinition EmitReceiverRef(BoundExpression receiver, AddressKind ad
                 return null;
             }
 
-            if (receiverType.TypeKind == TypeKind.TypeParameter)
+            if (BoxNonVerifierReferenceReceiver(receiverType, addressKind))
             {
                 //[Note: Constraints on a generic parameter only restrict the types that 
                 //the generic parameter may be instantiated with. Verification (see Partition III) 
@@ -514,26 +519,26 @@ private LocalDefinition EmitReceiverRef(BoundExpression receiver, AddressKind ad
                 //via the generic parameter unless it is first boxed (see Partition III) or 
                 //the callvirt instruction is prefixed with the constrained. prefix instruction 
                 //(see Partition III). end note]
-                if (addressKind == AddressKind.Constrained)
+                EmitExpression(receiver, used: true);
+                // conditional receivers are already boxed if needed when pushed
+                if (receiver.Kind != BoundKind.ConditionalReceiver)
                 {
-                    return EmitAddress(receiver, addressKind);
-                }
-                else
-                {
-                    EmitExpression(receiver, used: true);
-                    // conditional receivers are already boxed if needed when pushed
-                    if (receiver.Kind != BoundKind.ConditionalReceiver)
-                    {
-                        EmitBox(receiver.Type, receiver.Syntax);
-                    }
-                    return null;
+                    EmitBox(receiver.Type, receiver.Syntax);
                 }
+
+                return null;
             }
 
-            Debug.Assert(receiverType.IsVerifierValue());
+            Debug.Assert(receiverType.TypeKind == TypeKind.TypeParameter || receiverType.IsValueType);
             return EmitAddress(receiver, addressKind);
         }
 
+        private static bool BoxNonVerifierReferenceReceiver(TypeSymbol receiverType, AddressKind addressKind)
+        {
+            Debug.Assert(!receiverType.IsVerifierReference());
+            return receiverType.TypeKind == TypeKind.TypeParameter && addressKind != AddressKind.Constrained;
+        }
+
         /// <summary>
         /// May introduce a temp which it will return. (otherwise returns null)
         /// </summary>