Reimplement IOperation's Descendants extension methods using OperationWalker

And fixed some test failure caused by this.

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

@@ -135,9 +135,7 @@ public void M1(int z)
                 Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Bexley").WithLocation(7, 17),
                 Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "M1(y + d)").WithLocation(10, 9),
                 Diagnostic(BadStuffTestAnalyzer.InvalidStatementDescriptor.Id, "goto;").WithLocation(11, 9),
-                Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "goto;").WithLocation(11, 9),
-                Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "").WithLocation(11, 13),
-                Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "").WithLocation(11, 13)
+                Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "goto;").WithLocation(11, 9)
                 );
         }
 
@@ -1092,6 +1090,7 @@ class C
     public void OnMumble(System.EventArgs args)
     {
         Mumble += new MumbleEventHandler(Mumbler);
+        Mumble += (s, a) => {};
         Mumble(this, args);
         object o = Mumble;
         MumbleEventHandler d = Mumbler;
@@ -1108,11 +1107,12 @@ private void Mumbler(object sender, System.EventArgs args)
             .VerifyAnalyzerDiagnostics(new DiagnosticAnalyzer[] { new MemberReferenceAnalyzer() }, null, null, false,
                 Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "Mumble += new MumbleEventHandler(Mumbler)").WithLocation(10, 9),
                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(10, 42),
-                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(11, 9),
-                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(12, 20),
-                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(13, 32),
-                Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "Mumble -= new MumbleEventHandler(Mumbler)").WithLocation(15, 9),
-                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(15, 42)
+                Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "Mumble += (s, a) => {}").WithLocation(11, 9),
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(12, 9),
+                Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(13, 20),
+                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(14, 32),
+                Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "Mumble -= new MumbleEventHandler(Mumbler)").WithLocation(16, 9),
+                Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "Mumbler").WithLocation(16, 42)
                 );
         }
         

src/Compilers/Core/Portable/Compilation/OperationExtensions.cs

@@ -16,28 +16,27 @@ public static class OperationExtensions
     {
         public static IEnumerable<IOperation> Descendants(this IOperation operation)
         {
-            var searchable = operation as IOperationSearchable;
-            if (searchable != null)
-            {
-                return searchable.Descendants();
-            }
-            else
+            if (operation == null)
             {
                 return SpecializedCollections.EmptyEnumerable<IOperation>();
             }
+            var list = new List<IOperation>();
+            var collector = new OperationCollector(list);
+            collector.Visit(operation);
+            list.RemoveAt(0);
+            return list;
         }
 
         public static IEnumerable<IOperation> DescendantsAndSelf(this IOperation operation)
         {
-            var searchable = operation as IOperationSearchable;
-            if (searchable != null)
-            {
-                return searchable.DescendantsAndSelf();
-            }
-            else
+            if (operation == null)
             {
                 return SpecializedCollections.EmptyEnumerable<IOperation>();
             }
+            var list = new List<IOperation>();
+            var collector = new OperationCollector(list);
+            collector.Visit(operation);
+            return list;
         }
 
         public static IOperation GetRootOperation(this ISymbol symbol, CancellationToken cancellationToken = default(CancellationToken))
@@ -52,6 +51,25 @@ public static IOperation GetRootOperation(this ISymbol symbol, CancellationToken
                 return null;
             }
         }
+
+        private sealed class OperationCollector : OperationWalker
+        {
+            private readonly List<IOperation> _list;
+
+            public OperationCollector(List<IOperation> list)
+            {
+                _list = list;
+            }
+
+            public override void Visit(IOperation operation)
+            {
+                if (operation != null)
+                {
+                    _list.Add(operation);
+                }
+                base.Visit(operation);
+            }
+        }
     }
 
     internal interface ISymbolWithOperation

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

@@ -123,18 +123,12 @@ End Class
             comp.VerifyAnalyzerDiagnostics({New BadStuffTestAnalyzer}, Nothing, Nothing, False,
                                            Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "Framitz()").WithLocation(3, 9),
                                            Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Framitz()").WithLocation(3, 9),
-                                           Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "Framitz").WithLocation(3, 9),
-                                           Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Framitz").WithLocation(3, 9),
                                            Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "Bexley()").WithLocation(4, 28),
                                            Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Bexley()").WithLocation(4, 28),
-                                           Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "Bexley").WithLocation(4, 28),
-                                           Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Bexley").WithLocation(4, 28),
                                            Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "M1(d)").WithLocation(7, 9),
                                            Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "M1(d)").WithLocation(7, 9),
                                            Diagnostic(BadStuffTestAnalyzer.InvalidStatementDescriptor.Id, "Goto").WithLocation(8, 9),
-                                           Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Goto").WithLocation(8, 9),
-                                           Diagnostic(BadStuffTestAnalyzer.InvalidExpressionDescriptor.Id, "").WithLocation(8, 13),
-                                           Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "").WithLocation(8, 13))
+                                           Diagnostic(BadStuffTestAnalyzer.IsInvalidDescriptor.Id, "Goto").WithLocation(8, 9))
         End Sub
 
         <Fact>
@@ -1145,6 +1139,8 @@ Class C
 
     Public Sub OnMumble(args As System.EventArgs)
         AddHandler Mumble, New MumbleEventHandler(AddressOf Mumbler)
+        AddHandler Mumble, New MumbleEventHandler(Sub(s As Object, a As System.EventArgs)
+                                                  End Sub)
         RaiseEvent Mumble(Me, args)
         ' Dim o As object = AddressOf Mumble
         Dim d As MumbleEventHandler = AddressOf Mumbler
@@ -1163,13 +1159,13 @@ End Class
             comp.VerifyDiagnostics()
             comp.VerifyAnalyzerDiagnostics({New MemberReferenceAnalyzer}, Nothing, Nothing, False,
                  Diagnostic(MemberReferenceAnalyzer.HandlerAddedDescriptor.Id, "AddHandler Mumble, New MumbleEventHandler(AddressOf Mumbler)").WithLocation(7, 9),
-                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(7, 20),
                  Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(7, 51),
-                 Diagnostic(MemberReferenceAnalyzer.FieldReferenceDescriptor.Id, "Mumble").WithLocation(8, 20),
-                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(10, 39),
-                 Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "RemoveHandler Mumble, AddressOf Mumbler").WithLocation(12, 9),
-                 Diagnostic(MemberReferenceAnalyzer.EventReferenceDescriptor.Id, "Mumble").WithLocation(12, 23),
-                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(12, 31))
+                 Diagnostic("HandlerAdded", "AddHandler Mumble, New MumbleEventHandler(Sub(s As Object, a As System.EventArgs)
+                                                  End Sub)").WithLocation(8, 9),
+                 Diagnostic(MemberReferenceAnalyzer.FieldReferenceDescriptor.Id, "Mumble").WithLocation(10, 20),
+                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(12, 39),
+                 Diagnostic(MemberReferenceAnalyzer.HandlerRemovedDescriptor.Id, "RemoveHandler Mumble, AddressOf Mumbler").WithLocation(14, 9),
+                 Diagnostic(MemberReferenceAnalyzer.MethodBindingDescriptor.Id, "AddressOf Mumbler").WithLocation(14, 31))
         End Sub
 
         <Fact>