Ensure that EventAssignmentOperation always has a non-null EventRefer…

src/Compilers/CSharp/Portable/Operations/CSharpOperationFactory.cs

@@ -464,7 +464,7 @@ private IEventReferenceOperation CreateBoundEventAccessOperation(BoundEventAcces
 
         private IEventAssignmentOperation CreateBoundEventAssignmentOperatorOperation(BoundEventAssignmentOperator boundEventAssignmentOperator)
         {
-            Lazy<IEventReferenceOperation> eventReference = new Lazy<IEventReferenceOperation>(() => CreateBoundEventAccessOperation(boundEventAssignmentOperator));
+            Lazy<IOperation> eventReference = new Lazy<IOperation>(() => CreateBoundEventAccessOperation(boundEventAssignmentOperator));
             Lazy<IOperation> handlerValue = new Lazy<IOperation>(() => Create(boundEventAssignmentOperator.Argument));
             SyntaxNode syntax = boundEventAssignmentOperator.Syntax;
             bool adds = boundEventAssignmentOperator.IsAddition;

src/Compilers/Core/Portable/Generated/Operations.xml.Generated.cs

@@ -1681,7 +1681,7 @@ public override IEnumerable<IOperation> Children
         /// <summary>
         /// Instance used to refer to the event being bound.
         /// </summary>
-        public abstract IEventReferenceOperation EventReference { get; }
+        public abstract IOperation EventReference { get; }
 
         /// <summary>
         /// Handler supplied for the event.
@@ -1702,14 +1702,14 @@ public override void Accept(OperationVisitor visitor)
     /// </summary>
     internal sealed partial class EventAssignmentOperation : BaseEventAssignmentOperation, IEventAssignmentOperation
     {
-        public EventAssignmentOperation(IEventReferenceOperation eventReference, IOperation handlerValue, bool adds, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
+        public EventAssignmentOperation(IOperation eventReference, IOperation handlerValue, bool adds, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
             base(adds, semanticModel, syntax, type, constantValue, isImplicit)
         {
             EventReference = SetParentOperation(eventReference, this);
             HandlerValue = SetParentOperation(handlerValue, this);
         }
 
-        public override IEventReferenceOperation EventReference { get; }
+        public override IOperation EventReference { get; }
         public override IOperation HandlerValue { get; }
     }
 
@@ -1718,17 +1718,17 @@ internal sealed partial class EventAssignmentOperation : BaseEventAssignmentOper
     /// </summary>
     internal sealed partial class LazyEventAssignmentOperation : BaseEventAssignmentOperation, IEventAssignmentOperation
     {
-        private readonly Lazy<IEventReferenceOperation> _lazyEventReference;
+        private readonly Lazy<IOperation> _lazyEventReference;
         private readonly Lazy<IOperation> _lazyHandlerValue;
 
-        public LazyEventAssignmentOperation(Lazy<IEventReferenceOperation> eventReference, Lazy<IOperation> handlerValue, bool adds, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
+        public LazyEventAssignmentOperation(Lazy<IOperation> eventReference, Lazy<IOperation> handlerValue, bool adds, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue, bool isImplicit) :
             base(adds, semanticModel, syntax, type, constantValue, isImplicit)
         {
             _lazyEventReference = eventReference ?? throw new System.ArgumentNullException(nameof(eventReference));
             _lazyHandlerValue = handlerValue ?? throw new System.ArgumentNullException(nameof(handlerValue));
         }
 
-        public override IEventReferenceOperation EventReference => SetParentOperation(_lazyEventReference.Value, this);
+        public override IOperation EventReference => SetParentOperation(_lazyEventReference.Value, this);
         public override IOperation HandlerValue => SetParentOperation(_lazyHandlerValue.Value, this);
     }
 

src/Compilers/Core/Portable/Operations/ControlFlowGraphBuilder.cs

@@ -5042,18 +5042,59 @@ private void VisitInitializer(IOperation rewrittenTarget, ISymbolInitializerOper
 
         public override IOperation VisitEventAssignment(IEventAssignmentOperation operation, int? captureIdForResult)
         {
-            var instance = operation.EventReference.Event.IsStatic ? null : operation.EventReference.Instance;
-            if (instance != null)
+            IOperation visitedEventReference, visitedHandler;
+
+            // Get the IEventReferenceOperation, digging through IParenthesizedOperation.
+            // Note that for error cases, the event reference might be an IInvalidOperation.
+            IEventReferenceOperation eventReference = getEventReference();
+            if (eventReference != null)
             {
-                _evalStack.Push(Visit(instance));
+                // Preserve the IEventReferenceOperation.
+                var eventReferenceInstance = eventReference.Event.IsStatic ? null : eventReference.Instance;
+                if (eventReferenceInstance != null)
+                {
+                    _evalStack.Push(Visit(eventReferenceInstance));
+                }
+
+                visitedHandler = Visit(operation.HandlerValue);
+
+                IOperation visitedInstance = eventReferenceInstance == null ? null : _evalStack.Pop();
+                visitedEventReference = new EventReferenceExpression(eventReference.Event, visitedInstance,
+                    semanticModel: null, operation.EventReference.Syntax, operation.EventReference.Type, operation.EventReference.ConstantValue, IsImplicit(operation.EventReference));
             }
+            else
+            {
+                Debug.Assert(operation.EventReference != null);
+                Debug.Assert(operation.EventReference.Kind == OperationKind.Invalid);
 
-            IOperation visitedHandler = Visit(operation.HandlerValue);
-            IOperation visitedInstance = instance == null ? null : _evalStack.Pop();
-            var visitedEventReference = new EventReferenceExpression(operation.EventReference.Event, visitedInstance,
-                semanticModel: null, operation.EventReference.Syntax, operation.EventReference.Type, operation.EventReference.ConstantValue, IsImplicit(operation.EventReference));
+                _evalStack.Push(Visit(operation.EventReference));
+                visitedHandler = Visit(operation.HandlerValue);
+                visitedEventReference = _evalStack.Pop();
+            }
+
             return new EventAssignmentOperation(visitedEventReference, visitedHandler, operation.Adds, semanticModel: null,
                 operation.Syntax, operation.Type, operation.ConstantValue, IsImplicit(operation));
+
+            IEventReferenceOperation getEventReference()
+            {
+                IOperation current = operation.EventReference;
+
+                while (true)
+                {
+                    switch (current.Kind)
+                    {
+                        case OperationKind.EventReference:
+                            return (IEventReferenceOperation)current;
+
+                        case OperationKind.Parenthesized:
+                            current = ((IParenthesizedOperation)current).Operand;
+                            continue;
+
+                        default:
+                            return null;
+                    }
+                }
+            }
         }
 
         public override IOperation VisitRaiseEvent(IRaiseEventOperation operation, int? captureIdForResult)

src/Compilers/Core/Portable/Operations/IEventAssignmentOperation.cs

@@ -19,7 +19,7 @@ public interface IEventAssignmentOperation : IOperation
         /// <summary>
         /// Reference to the event being bound.
         /// </summary>
-        IEventReferenceOperation EventReference { get; }
+        IOperation EventReference { get; }
 
         /// <summary>
         /// Handler supplied for the event.

src/Compilers/Core/Portable/PublicAPI.Shipped.txt

@@ -1402,7 +1402,6 @@ Microsoft.CodeAnalysis.Operations.IEmptyOperation
 Microsoft.CodeAnalysis.Operations.IEndOperation
 Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation
 Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation.Adds.get -> bool
-Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation.EventReference.get -> Microsoft.CodeAnalysis.Operations.IEventReferenceOperation
 Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation.HandlerValue.get -> Microsoft.CodeAnalysis.IOperation
 Microsoft.CodeAnalysis.Operations.IEventReferenceOperation
 Microsoft.CodeAnalysis.Operations.IEventReferenceOperation.Event.get -> Microsoft.CodeAnalysis.IEventSymbol

src/Compilers/Core/Portable/PublicAPI.Unshipped.txt

@@ -1,3 +1,4 @@
+*REMOVED*Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation.EventReference.get -> Microsoft.CodeAnalysis.Operations.IEventReferenceOperation
 Microsoft.CodeAnalysis.CompilationOptions.MetadataImportOptions.get -> Microsoft.CodeAnalysis.MetadataImportOptions
 Microsoft.CodeAnalysis.CompilationOptions.WithMetadataImportOptions(Microsoft.CodeAnalysis.MetadataImportOptions value) -> Microsoft.CodeAnalysis.CompilationOptions
 Microsoft.CodeAnalysis.Emit.EmitOptions.EmitOptions(bool metadataOnly = false, Microsoft.CodeAnalysis.Emit.DebugInformationFormat debugInformationFormat = (Microsoft.CodeAnalysis.Emit.DebugInformationFormat)0, string pdbFilePath = null, string outputNameOverride = null, int fileAlignment = 0, ulong baseAddress = 0, bool highEntropyVirtualAddressSpace = false, Microsoft.CodeAnalysis.SubsystemVersion subsystemVersion = default(Microsoft.CodeAnalysis.SubsystemVersion), string runtimeMetadataVersion = null, bool tolerateErrors = false, bool includePrivateMembers = true, System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Emit.InstrumentationKind> instrumentationKinds = default(System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.Emit.InstrumentationKind>), System.Security.Cryptography.HashAlgorithmName? pdbChecksumAlgorithm = null) -> void
@@ -80,6 +81,7 @@ Microsoft.CodeAnalysis.Operations.IConstructorBodyOperation.Initializer.get -> M
 Microsoft.CodeAnalysis.Operations.IConstructorBodyOperation.Locals.get -> System.Collections.Immutable.ImmutableArray<Microsoft.CodeAnalysis.ILocalSymbol>
 Microsoft.CodeAnalysis.Operations.IDiscardOperation
 Microsoft.CodeAnalysis.Operations.IDiscardOperation.DiscardSymbol.get -> Microsoft.CodeAnalysis.IDiscardSymbol
+Microsoft.CodeAnalysis.Operations.IEventAssignmentOperation.EventReference.get -> Microsoft.CodeAnalysis.IOperation
 Microsoft.CodeAnalysis.Operations.IFlowCaptureOperation
 Microsoft.CodeAnalysis.Operations.IFlowCaptureOperation.Id.get -> int
 Microsoft.CodeAnalysis.Operations.IFlowCaptureOperation.Value.get -> Microsoft.CodeAnalysis.IOperation

src/Compilers/Test/Utilities/VisualBasic/BasicTestBase.vb

@@ -826,9 +826,12 @@ Public MustInherit Class BasicTestBase
 
     Protected Shared Sub VerifyFlowGraphForTest(Of TSyntaxNode As SyntaxNode)(compilation As VisualBasicCompilation, expectedFlowGraph As String, Optional which As Integer = 0)
         Dim tree = compilation.SyntaxTrees(0)
-        Dim model = compilation.GetSemanticModel(tree)
         Dim syntaxNode As SyntaxNode = CompilationUtils.FindBindingText(Of TSyntaxNode)(compilation, tree.FilePath, which, prefixMatch:=True)
+        VerifyFlowGraph(compilation, syntaxNode, expectedFlowGraph)
+    End Sub
 
+    Protected Shared Sub VerifyFlowGraph(compilation As VisualBasicCompilation, syntaxNode As SyntaxNode, expectedFlowGraph As String)
+        Dim model = compilation.GetSemanticModel(syntaxNode.SyntaxTree)
         Dim graph As Operations.ControlFlowGraph = ControlFlowGraphVerifier.GetControlFlowGraph(syntaxNode, model)
         ControlFlowGraphVerifier.VerifyGraph(compilation, expectedFlowGraph, graph)
     End Sub
@@ -865,9 +868,9 @@ Public MustInherit Class BasicTestBase
         VerifyOperationTreeForTest(Of TSyntaxNode)(compilation, fileName, expectedOperationTree, which, additionalOperationTreeVerifier)
     End Sub
 
-    Friend Shared Sub VerifyFlowGraphAndDiagnosticsForTest(Of TSyntaxNode As SyntaxNode)(compilation As VisualBasicCompilation, expectedOperationTree As String, expectedDiagnostics As String, Optional which As Integer = 0)
+    Friend Shared Sub VerifyFlowGraphAndDiagnosticsForTest(Of TSyntaxNode As SyntaxNode)(compilation As VisualBasicCompilation, expectedFlowGraph As String, expectedDiagnostics As String, Optional which As Integer = 0)
         compilation.AssertTheseDiagnostics(FilterString(expectedDiagnostics))
-        VerifyFlowGraphForTest(Of TSyntaxNode)(compilation, expectedOperationTree, which)
+        VerifyFlowGraphForTest(Of TSyntaxNode)(compilation, expectedFlowGraph, which)
     End Sub
 
     Friend Shared Sub VerifyOperationTreeAndDiagnosticsForTest(Of TSyntaxNode As SyntaxNode)(
@@ -892,7 +895,7 @@ Public MustInherit Class BasicTestBase
 
     Friend Shared Sub VerifyFlowGraphAndDiagnosticsForTest(Of TSyntaxNode As SyntaxNode)(
         testSrc As String,
-        expectedOperationTree As String,
+        expectedFlowGraph As String,
         expectedDiagnostics As String,
         Optional compilationOptions As VisualBasicCompilationOptions = Nothing,
         Optional parseOptions As VisualBasicParseOptions = Nothing,
@@ -907,7 +910,7 @@ Public MustInherit Class BasicTestBase
         Dim references = defaultRefs.Concat({ValueTupleRef, SystemRuntimeFacadeRef})
         references = If(additionalReferences IsNot Nothing, references.Concat(additionalReferences), references)
         Dim compilation = CreateCompilationWithMscorlib45AndVBRuntime({syntaxTree}, references:=references, options:=If(compilationOptions, TestOptions.ReleaseDll))
-        VerifyFlowGraphAndDiagnosticsForTest(Of TSyntaxNode)(compilation, expectedOperationTree, expectedDiagnostics, which)
+        VerifyFlowGraphAndDiagnosticsForTest(Of TSyntaxNode)(compilation, expectedFlowGraph, expectedDiagnostics, which)
     End Sub
 
 

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory_Methods.vb

@@ -421,11 +421,11 @@ Namespace Microsoft.CodeAnalysis.Operations
         End Function
 
         Private Function GetAddRemoveHandlerStatementExpression(statement As BoundAddRemoveHandlerStatement) As IOperation
-            Dim eventAccess As BoundEventAccess = TryCast(statement.EventAccess, BoundEventAccess)
-            Dim eventReference = If(eventAccess Is Nothing, Nothing, CreateBoundEventAccessOperation(eventAccess))
+            Dim eventAccess As IOperation = Create(statement.EventAccess)
+            Dim handler As IOperation = Create(statement.Handler)
             Dim adds = statement.Kind = BoundKind.AddHandlerStatement
             Return New EventAssignmentOperation(
-                eventReference, Create(statement.Handler), adds:=adds, semanticModel:=_semanticModel, syntax:=statement.Syntax, type:=Nothing, constantValue:=Nothing, isImplicit:=True)
+                eventAccess, handler, adds:=adds, semanticModel:=_semanticModel, syntax:=statement.Syntax, type:=Nothing, constantValue:=Nothing, isImplicit:=True)
         End Function
 
 #Region "Conversions"