Address review comments

src/Compilers/CSharp/Test/Semantic/Diagnostics/OperationAnalyzerTests.cs

@@ -1125,7 +1125,7 @@ public override void M1()
                 );
         }
 
-        [Fact(Skip = "https://github.com/dotnet/roslyn/issues/18839")]
+        [Fact]
         public void EventAndMethodReferencesCSharp()
         {
             const string source = @"
@@ -1154,21 +1154,18 @@ private void Mumbler(object sender, System.EventArgs args)
             CreateCompilationWithMscorlib45(source, parseOptions: TestOptions.RegularWithIOperationFeature)
             .VerifyDiagnostics()
             .VerifyAnalyzerDiagnostics(new DiagnosticAnalyzer[] { new MemberReferenceAnalyzer() }, null, null, false,
+                // Bug: we are missing diagnostics of "MethodBindingDescriptor" here. https://github.com/dotnet/roslyn/issues/20095
                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "Mumble += new MumbleEventHandler(Mumbler)").WithLocation(10, 9),
-                // Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
-                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(10, 42),
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(10, 9),
                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "Mumble += (s, a) => {}").WithLocation(11, 9),
-                // Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(11, 9),
                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "Mumble += new MumbleEventHandler((s, a) => {})").WithLocation(12, 9),
-                // Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
-                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "(s, a) => {}").WithLocation(12, 42),   // Bug: this is not a method binding https://github.com/dotnet/roslyn/issues/8347
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(12, 9),
                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(13, 9),
                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(14, 20),
                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(15, 32),
                 Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "Mumble -= new MumbleEventHandler(Mumbler)").WithLocation(17, 9),
-                // Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
-                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(17, 42)
-                );
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(17, 9));
         }
 
         [Fact]

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

@@ -409,7 +409,7 @@ Namespace Microsoft.CodeAnalysis.Semantics
         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 adds = TypeOf statement Is BoundAddHandlerStatement
+            Dim adds = statement.Kind = BoundKind.AddHandlerStatement
             Return New EventAssignmentExpression(
                 eventReference, Create(statement.Handler), adds:=adds, syntax:=statement.Syntax, type:=Nothing, constantValue:=Nothing)
         End Function

src/Compilers/VisualBasic/Test/Semantic/Diagnostics/OperationAnalyzerTests.vb

@@ -1146,7 +1146,7 @@ End Class
                Diagnostic(ExplicitVsImplicitInstanceAnalyzer.ImplicitInstanceDescriptor.Id, "M2").WithLocation(15, 9))
         End Sub
 
-        <Fact(Skip:="https://github.com/dotnet/roslyn/issues/18839")>
+        <Fact>
         Public Sub EventAndMethodReferencesVisualBasic()
             Dim source = <compilation>
                              <file name="c.vb">
@@ -1178,17 +1178,19 @@ End Class
 
             Dim comp = CompilationUtils.CreateCompilationWithMscorlibAndVBRuntime(source, parseOptions:=TestOptions.RegularWithIOperationFeature)
             comp.VerifyDiagnostics()
-            comp.VerifyAnalyzerDiagnostics({New MemberReferenceAnalyzer}, Nothing, Nothing, False,
-                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "AddHandler Mumble, New MumbleEventHandler(AddressOf Mumbler)").WithLocation(7, 9),  ' Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
-                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(7, 51),
+            comp.VerifyAnalyzerDiagnostics({New MemberReferenceAnalyzer}, Nothing, Nothing, False,                 ' Bug: we are missing diagnostics of "MethodBindingDescriptor" here. https://github.com/dotnet/roslyn/issues/20095                           
+                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "AddHandler Mumble, New MumbleEventHandler(AddressOf Mumbler)").WithLocation(7, 9),
+                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(7, 20),
                  Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "AddHandler Mumble, New MumbleEventHandler(Sub(s As Object, a As System.EventArgs)
-                                                  End Sub)").WithLocation(8, 9),                                                                                    ' Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
+                                                  End Sub)").WithLocation(8, 9),
+                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(8, 20),
                  Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "AddHandler Mumble, Sub(s As Object, a As System.EventArgs)
-                           End Sub").WithLocation(10, 9),                                                                                                           ' Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
+                           End Sub").WithLocation(10, 9),
+                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(10, 20),
                  Diagnostic(MemberReferenceAnalyzer.FieldReferenceDescriptor.Id, "Mumble").WithLocation(12, 20),   ' Bug: This should be an event reference. https://github.com/dotnet/roslyn/issues/8345
-                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(14, 39),
-                 Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "RemoveHandler Mumble, AddressOf Mumbler").WithLocation(16, 9),                    ' Bug: Missing a EventReferenceExpression here https://github.com/dotnet/roslyn/issues/8346
-                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(16, 31))
+                 Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "RemoveHandler Mumble, AddressOf Mumbler").WithLocation(16, 9),
+                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(16, 23)
+            )
         End Sub
 
         <Fact>

src/Test/Utilities/Portable/Diagnostics/OperationTestAnalyzer.cs

@@ -1060,13 +1060,9 @@ public sealed override void Initialize(AnalysisContext context)
                      IEventAssignmentExpression eventAssignment = (IEventAssignmentExpression)operationContext.Operation;
                      operationContext.ReportDiagnostic(Diagnostic.Create(eventAssignment.Adds ? HandlerAddedDescriptor : HandlerRemovedDescriptor, operationContext.Operation.Syntax.GetLocation()));
 
-                     if (eventAssignment.EventReference?.Event == null)
+                     if (eventAssignment.EventReference?.Event == null && eventAssignment.HasErrors(operationContext.Compilation, operationContext.CancellationToken))
                      {
-                         if (eventAssignment.EventReference?.Instance == null && eventAssignment.HasErrors(operationContext.Compilation, operationContext.CancellationToken))
-                         {
-                             // report inside after checking for null to make sure it does't crash.
-                             operationContext.ReportDiagnostic(Diagnostic.Create(InvalidEventDescriptor, eventAssignment.Syntax.GetLocation()));
-                         }
+                         operationContext.ReportDiagnostic(Diagnostic.Create(InvalidEventDescriptor, eventAssignment.Syntax.GetLocation()));
                      }
                  },
                  OperationKind.EventAssignmentExpression);