Merge pull request #41959 from CyrusNajmabadi/simplifyImplementAbstract

Share more code between Implement-Abstract-Class and Implement-Interface

src/EditorFeatures/CSharpTest/ImplementAbstractClass/ImplementAbstractClassTests.cs

@@ -1822,5 +1822,29 @@ public override void M<T>()
     }
 }");
         }
+
+        [Fact]
+        public async Task NothingOfferedWhenInheritanceIsPreventedByInternalAbstractMember()
+        {
+            await TestMissingAsync(
+@"<Workspace>
+    <Project Language=""C#"" AssemblyName=""Assembly1"" CommonReferences=""true"">
+        <Document>
+public abstract class Base
+{
+    internal abstract void Method();
+}
+        </Document>
+    </Project>
+    <Project Language=""C#"" AssemblyName=""Assembly2"" CommonReferences=""true"">
+        <Document>
+class [|Derived|] : Base
+{
+    Base inner;
+}
+        </Document>
+    </Project>
+</Workspace>");
+        }
     }
 }

src/EditorFeatures/CSharpTest/ImplementInterface/ImplementInterfaceTests.cs

@@ -1825,18 +1825,18 @@ public int Count
     {
         get
         {
-            return ((IReadOnlyList<int>)field).Count;
+            return ((IReadOnlyCollection<int>)field).Count;
         }
     }
 
     public IEnumerator<int> GetEnumerator()
     {
-        return ((IReadOnlyList<int>)field).GetEnumerator();
+        return ((IEnumerable<int>)field).GetEnumerator();
     }
 
     IEnumerator IEnumerable.GetEnumerator()
     {
-        return ((IReadOnlyList<int>)field).GetEnumerator();
+        return field.GetEnumerator();
     }
 }",
 index: 1);
@@ -1870,7 +1870,7 @@ public int Count
     {
         get
         {
-            return ((IReadOnlyList<int>)field).Count;
+            return ((IReadOnlyCollection<int>)field).Count;
         }
     }
 
@@ -1878,12 +1878,12 @@ public int Count
 
     public IEnumerator<int> GetEnumerator()
     {
-        return ((IReadOnlyList<int>)field).GetEnumerator();
+        return ((IEnumerable<int>)field).GetEnumerator();
     }
 
     IEnumerator IEnumerable.GetEnumerator()
     {
-        return ((IReadOnlyList<int>)field).GetEnumerator();
+        return field.GetEnumerator();
     }
 }",
 index: 1);
@@ -6668,7 +6668,7 @@ public int Count
     {
         get
         {
-            return ((IList<object>)innerList).Count;
+            return ((ICollection<object>)innerList).Count;
         }
     }
 
@@ -6676,33 +6676,33 @@ public bool IsReadOnly
     {
         get
         {
-            return ((IList<object>)innerList).IsReadOnly;
+            return ((ICollection<object>)innerList).IsReadOnly;
         }
     }
 
     public void Add(object item)
     {
-        ((IList<object>)innerList).Add(item);
+        ((ICollection<object>)innerList).Add(item);
     }
 
     public void Clear()
     {
-        ((IList<object>)innerList).Clear();
+        ((ICollection<object>)innerList).Clear();
     }
 
     public bool Contains(object item)
     {
-        return ((IList<object>)innerList).Contains(item);
+        return ((ICollection<object>)innerList).Contains(item);
     }
 
     public void CopyTo(object[] array, int arrayIndex)
     {
-        ((IList<object>)innerList).CopyTo(array, arrayIndex);
+        ((ICollection<object>)innerList).CopyTo(array, arrayIndex);
     }
 
     public IEnumerator<object> GetEnumerator()
     {
-        return ((IList<object>)innerList).GetEnumerator();
+        return ((IEnumerable<object>)innerList).GetEnumerator();
     }
 
     public int IndexOf(object item)
@@ -6717,7 +6717,7 @@ public void Insert(int index, object item)
 
     public bool Remove(object item)
     {
-        return ((IList<object>)innerList).Remove(item);
+        return ((ICollection<object>)innerList).Remove(item);
     }
 
     public void RemoveAt(int index)
@@ -6727,7 +6727,7 @@ public void RemoveAt(int index)
 
     IEnumerator IEnumerable.GetEnumerator()
     {
-        return ((IList<object>)innerList).GetEnumerator();
+        return ((IEnumerable)innerList).GetEnumerator();
     }
 }",
 index: 1);

src/EditorFeatures/VisualBasicTest/ImplementInterface/ImplementInterfaceTests.vb

@@ -967,16 +967,16 @@ Class A
 
     Public ReadOnly Property Count As Integer Implements IReadOnlyCollection(Of Integer).Count
         Get
-            Return DirectCast(field, IReadOnlyList(Of Integer)).Count
+            Return DirectCast(field, IReadOnlyCollection(Of Integer)).Count
         End Get
     End Property
 
     Public Function GetEnumerator() As IEnumerator(Of Integer) Implements IEnumerable(Of Integer).GetEnumerator
-        Return DirectCast(field, IReadOnlyList(Of Integer)).GetEnumerator()
+        Return DirectCast(field, IEnumerable(Of Integer)).GetEnumerator()
     End Function
 
     Private Function IEnumerable_GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator
-        Return DirectCast(field, IReadOnlyList(Of Integer)).GetEnumerator()
+        Return field.GetEnumerator()
     End Function
 End Class",
 index:=1)
@@ -1004,18 +1004,18 @@ Class A
 
     Public ReadOnly Property Count As Integer Implements IReadOnlyCollection(Of Integer).Count
         Get
-            Return DirectCast(field, IReadOnlyList(Of Integer)).Count
+            Return DirectCast(field, IReadOnlyCollection(Of Integer)).Count
         End Get
     End Property
 
     Private Property field As Integer()
 
     Public Function GetEnumerator() As IEnumerator(Of Integer) Implements IEnumerable(Of Integer).GetEnumerator
-        Return DirectCast(field, IReadOnlyList(Of Integer)).GetEnumerator()
+        Return DirectCast(field, IEnumerable(Of Integer)).GetEnumerator()
     End Function
 
     Private Function IEnumerable_GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator
-        Return DirectCast(field, IReadOnlyList(Of Integer)).GetEnumerator()
+        Return field.GetEnumerator()
     End Function
 End Class",
 index:=1)
@@ -4483,13 +4483,13 @@ Class Program(Of T)
 
     Public ReadOnly Property Count As Integer Implements ICollection(Of Object).Count
         Get
-            Return DirectCast(innerList, IList(Of Object)).Count
+            Return DirectCast(innerList, ICollection(Of Object)).Count
         End Get
     End Property
 
     Public ReadOnly Property IsReadOnly As Boolean Implements ICollection(Of Object).IsReadOnly
         Get
-            Return DirectCast(innerList, IList(Of Object)).IsReadOnly
+            Return DirectCast(innerList, ICollection(Of Object)).IsReadOnly
         End Get
     End Property
 
@@ -4502,15 +4502,15 @@ Class Program(Of T)
     End Sub
 
     Public Sub Add(item As Object) Implements ICollection(Of Object).Add
-        DirectCast(innerList, IList(Of Object)).Add(item)
+        DirectCast(innerList, ICollection(Of Object)).Add(item)
     End Sub
 
     Public Sub Clear() Implements ICollection(Of Object).Clear
-        DirectCast(innerList, IList(Of Object)).Clear()
+        DirectCast(innerList, ICollection(Of Object)).Clear()
     End Sub
 
     Public Sub CopyTo(array() As Object, arrayIndex As Integer) Implements ICollection(Of Object).CopyTo
-        DirectCast(innerList, IList(Of Object)).CopyTo(array, arrayIndex)
+        DirectCast(innerList, ICollection(Of Object)).CopyTo(array, arrayIndex)
     End Sub
 
     Public Function IndexOf(item As Object) As Integer Implements IList(Of Object).IndexOf
@@ -4518,19 +4518,19 @@ Class Program(Of T)
     End Function
 
     Public Function Contains(item As Object) As Boolean Implements ICollection(Of Object).Contains
-        Return DirectCast(innerList, IList(Of Object)).Contains(item)
+        Return DirectCast(innerList, ICollection(Of Object)).Contains(item)
     End Function
 
     Public Function Remove(item As Object) As Boolean Implements ICollection(Of Object).Remove
-        Return DirectCast(innerList, IList(Of Object)).Remove(item)
+        Return DirectCast(innerList, ICollection(Of Object)).Remove(item)
     End Function
 
     Public Function GetEnumerator() As IEnumerator(Of Object) Implements IEnumerable(Of Object).GetEnumerator
-        Return DirectCast(innerList, IList(Of Object)).GetEnumerator()
+        Return DirectCast(innerList, IEnumerable(Of Object)).GetEnumerator()
     End Function
 
     Private Function IEnumerable_GetEnumerator() As IEnumerator Implements IEnumerable.GetEnumerator
-        Return DirectCast(innerList, IList(Of Object)).GetEnumerator()
+        Return DirectCast(innerList, IEnumerable).GetEnumerator()
     End Function
 End Class",
 index:=1)

src/Features/Core/Portable/FeaturesResources.resx

@@ -1732,12 +1732,6 @@ This version used in: {2}</value>
   <data name="Implement_implicitly" xml:space="preserve">
     <value>Implement implicitly</value>
   </data>
-  <data name="Implement all interfaces explicitly" xml:space="preserve">
-    <value>Implement all interfaces explicitly</value>
-  </data>
-  <data name="Implement explicitly" xml:space="preserve">
-    <value>Implement explicitly</value>
-  </data>
   <data name="Implement_0_explicitly" xml:space="preserve">
     <value>Implement '{0}' explicitly</value>
   </data>
@@ -1753,4 +1747,13 @@ This version used in: {2}</value>
   <data name="Value_colon" xml:space="preserve">
     <value>Value:</value>
   </data>
+  <data name="Implement_through_0" xml:space="preserve">
+    <value>Implement through '{0}'</value>
+  </data>
+  <data name="Implement_all_interfaces_explicitly" xml:space="preserve">
+    <value>Implement all interfaces explicitly</value>
+  </data>
+  <data name="Implement_explicitly" xml:space="preserve">
+    <value>Implement explicitly</value>
+  </data>
 </root>
\ No newline at end of file

src/Features/Core/Portable/ImplementAbstractClass/AbstractImplementAbstractClassCodeFixProvider.cs

@@ -19,8 +19,8 @@ internal abstract class AbstractImplementAbstractClassCodeFixProvider<TClassNode
     {
         public sealed override ImmutableArray<string> FixableDiagnosticIds { get; }
 
-        public sealed override FixAllProvider GetFixAllProvider() =>
-            WellKnownFixAllProviders.BatchFixer;
+        public sealed override FixAllProvider GetFixAllProvider()
+            => WellKnownFixAllProviders.BatchFixer;
 
         protected AbstractImplementAbstractClassCodeFixProvider(string diagnosticId)
             => FixableDiagnosticIds = ImmutableArray.Create(diagnosticId);
@@ -44,10 +44,11 @@ public sealed override async Task RegisterCodeFixesAsync(CodeFixContext context)
             if (data == null)
                 return;
 
-            var abstractClassType = data.ClassType.BaseType!;
+            var abstractClassType = data.AbstractClassType;
             var id = GetCodeActionId(abstractClassType.ContainingAssembly.Name, abstractClassType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat));
             context.RegisterCodeFix(
                 new MyCodeAction(
+                    FeaturesResources.Implement_abstract_class,
                     c => data.ImplementAbstractClassAsync(c), id),
                 context.Diagnostics);
         }
@@ -57,8 +58,8 @@ private static string GetCodeActionId(string assemblyName, string abstractTypeFu
 
         private class MyCodeAction : CodeAction.DocumentChangeAction
         {
-            public MyCodeAction(Func<CancellationToken, Task<Document>> createChangedDocument, string id)
-                : base(FeaturesResources.Implement_abstract_class, createChangedDocument, id)
+            public MyCodeAction(string title, Func<CancellationToken, Task<Document>> createChangedDocument, string id)
+                : base(title, createChangedDocument, id)
             {
             }
         }

src/Features/Core/Portable/ImplementAbstractClass/ImplementAbstractClassData.cs

@@ -4,6 +4,8 @@
 
 #nullable enable
 
+using System;
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
@@ -24,14 +26,16 @@ internal class ImplementAbstractClassData
         private readonly ImmutableArray<(INamedTypeSymbol type, ImmutableArray<ISymbol> members)> _unimplementedMembers;
 
         public readonly INamedTypeSymbol ClassType;
+        public readonly INamedTypeSymbol AbstractClassType;
 
         public ImplementAbstractClassData(
-            Document document, SyntaxNode classNode, INamedTypeSymbol classType,
+            Document document, SyntaxNode classNode, INamedTypeSymbol classType, INamedTypeSymbol abstractClassType,
             ImmutableArray<(INamedTypeSymbol type, ImmutableArray<ISymbol> members)> unimplementedMembers)
         {
             _document = document;
             _classNode = classNode;
             ClassType = classType;
+            AbstractClassType = abstractClassType;
             _unimplementedMembers = unimplementedMembers;
         }
 
@@ -57,7 +61,7 @@ internal class ImplementAbstractClassData
             if (unimplementedMembers.IsEmpty)
                 return null;
 
-            return new ImplementAbstractClassData(document, classNode, classType, unimplementedMembers);
+            return new ImplementAbstractClassData(document, classNode, classType, abstractClassType, unimplementedMembers);
         }
 
         public static async Task<Document?> TryImplementAbstractClassAsync(Document document, SyntaxNode classNode, CancellationToken cancellationToken)
@@ -129,18 +133,18 @@ public async Task<Document> ImplementAbstractClassAsync(CancellationToken cancel
             {
                 IMethodSymbol method => GenerateMethod(compilation, method, modifiers, accessibility),
                 IPropertySymbol property => GenerateProperty(compilation, property, modifiers, accessibility, propertyGenerationBehavior),
-                IEventSymbol @event => CodeGenerationSymbolFactory.CreateEventSymbol(
-                    @event, accessibility: accessibility, modifiers: modifiers),
+                IEventSymbol @event => GenerateEvent(@event, accessibility, modifiers),
                 _ => null,
             };
         }
 
         private ISymbol GenerateMethod(
-            Compilation compilation, IMethodSymbol method, DeclarationModifiers modifiers, Accessibility accessibility)
+            Compilation compilation, IMethodSymbol method,
+            DeclarationModifiers modifiers, Accessibility accessibility)
         {
             var syntaxFacts = _document.GetRequiredLanguageService<ISyntaxFactsService>();
-            var syntaxFactory = _document.GetRequiredLanguageService<SyntaxGenerator>();
-            var throwingBody = syntaxFactory.CreateThrowNotImplementedStatementBlock(compilation);
+            var generator = _document.GetRequiredLanguageService<SyntaxGenerator>();
+            var body = generator.CreateThrowNotImplementedStatement(compilation);
 
             method = method.EnsureNonConflictingNames(this.ClassType, syntaxFacts);
 
@@ -148,7 +152,7 @@ public async Task<Document> ImplementAbstractClassAsync(CancellationToken cancel
                 method,
                 accessibility: accessibility,
                 modifiers: modifiers,
-                statements: throwingBody);
+                statements: ImmutableArray.Create(body));
         }
 
         private IPropertySymbol GenerateProperty(
@@ -164,18 +168,16 @@ public async Task<Document> ImplementAbstractClassAsync(CancellationToken cancel
                 propertyGenerationBehavior = ImplementTypePropertyGenerationBehavior.PreferThrowingProperties;
             }
 
-            var syntaxFactory = _document.GetLanguageService<SyntaxGenerator>();
-
-            var accessorBody = propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties
-                ? default
-                : syntaxFactory.CreateThrowNotImplementedStatementBlock(compilation);
+            var generator = _document.GetRequiredLanguageService<SyntaxGenerator>();
+            var preferAutoProperties = propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties;
 
             var getMethod = ShouldGenerateAccessor(property.GetMethod)
                 ? CodeGenerationSymbolFactory.CreateAccessorSymbol(
                     property.GetMethod,
                     attributes: default,
                     accessibility: property.GetMethod.ComputeResultantAccessibility(this.ClassType),
-                    statements: accessorBody)
+                    statements: generator.GetGetAccessorStatements(
+                        compilation, property, throughMember: null, preferAutoProperties))
                 : null;
 
             var setMethod = ShouldGenerateAccessor(property.SetMethod)
@@ -183,7 +185,8 @@ public async Task<Document> ImplementAbstractClassAsync(CancellationToken cancel
                     property.SetMethod,
                     attributes: default,
                     accessibility: property.SetMethod.ComputeResultantAccessibility(this.ClassType),
-                    statements: accessorBody)
+                    statements: generator.GetSetAccessorStatements(
+                        compilation, property, throughMember: null, preferAutoProperties))
                 : null;
 
             return CodeGenerationSymbolFactory.CreatePropertySymbol(
@@ -194,6 +197,14 @@ public async Task<Document> ImplementAbstractClassAsync(CancellationToken cancel
                 setMethod: setMethod);
         }
 
+        private IEventSymbol GenerateEvent(
+            IEventSymbol @event, Accessibility accessibility, DeclarationModifiers modifiers)
+        {
+            var generator = _document.GetRequiredLanguageService<SyntaxGenerator>();
+            return CodeGenerationSymbolFactory.CreateEventSymbol(
+                @event, accessibility: accessibility, modifiers: modifiers);
+        }
+
         private bool ShouldGenerateAccessor(IMethodSymbol? method)
             => method != null && this.ClassType.FindImplementationForAbstractMember(method) == null;
     }

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.CodeAction.cs

@@ -99,7 +99,7 @@ public override string Title
                     }
                     else if (ThroughMember != null)
                     {
-                        return string.Format(FeaturesResources.Implement_interface_through_0, GetDescription(ThroughMember));
+                        return string.Format(FeaturesResources.Implement_interface_through_0, ThroughMember.Name);
                     }
                     else
                     {
@@ -144,14 +144,6 @@ public override string Title
 
             public override string EquivalenceKey => _equivalenceKey;
 
-            private static string GetDescription(ISymbol throughMember)
-                => throughMember switch
-                {
-                    IFieldSymbol field => field.Name,
-                    IPropertySymbol property => property.Name,
-                    _ => throw new InvalidOperationException(),
-                };
-
             protected override Task<Document> GetChangedDocumentAsync(CancellationToken cancellationToken)
             {
                 return GetUpdatedDocumentAsync(cancellationToken);
@@ -390,44 +382,42 @@ private static bool IsUnexpressibleTypeParameter(ITypeParameterSymbol typeParame
                     ? Accessibility.Public
                     : Accessibility.Private;
 
-                switch (member)
+                return member switch
                 {
-                    case IMethodSymbol method:
-                        return GenerateMethod(compilation, method, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, cancellationToken);
-
-                    case IPropertySymbol property:
-                        return GenerateProperty(compilation, property, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, propertyGenerationBehavior, cancellationToken);
-
-                    case IEventSymbol @event:
-                        var accessor = CodeGenerationSymbolFactory.CreateAccessorSymbol(
-                            attributes: default,
-                            accessibility: Accessibility.NotApplicable,
-                            statements: factory.CreateThrowNotImplementedStatementBlock(compilation));
-
-                        return CodeGenerationSymbolFactory.CreateEventSymbol(
-                            @event,
-                            accessibility: accessibility,
-                            modifiers: modifiers,
-                            explicitInterfaceImplementations: useExplicitInterfaceSymbol ? ImmutableArray.Create(@event) : default,
-                            name: memberName,
-                            addMethod: GetAddOrRemoveMethod(generateInvisibly, accessor, memberName, factory.AddEventHandler),
-                            removeMethod: GetAddOrRemoveMethod(generateInvisibly, accessor, memberName, factory.RemoveEventHandler));
-                }
+                    IMethodSymbol method => GenerateMethod(compilation, method, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName),
+                    IPropertySymbol property => GenerateProperty(compilation, property, accessibility, modifiers, generateAbstractly, useExplicitInterfaceSymbol, memberName, propertyGenerationBehavior, cancellationToken),
+                    IEventSymbol @event => GenerateEvent(compilation, memberName, generateInvisibly, factory, modifiers, useExplicitInterfaceSymbol, accessibility, @event),
+                    _ => null,
+                };
+            }
 
-                return null;
+            private ISymbol GenerateEvent(Compilation compilation, string memberName, bool generateInvisibly, SyntaxGenerator factory, DeclarationModifiers modifiers, bool useExplicitInterfaceSymbol, Accessibility accessibility, IEventSymbol @event)
+            {
+                var accessor = CodeGenerationSymbolFactory.CreateAccessorSymbol(
+                    attributes: default,
+                    accessibility: Accessibility.NotApplicable,
+                    statements: factory.CreateThrowNotImplementedStatementBlock(compilation));
+
+                return CodeGenerationSymbolFactory.CreateEventSymbol(
+                    @event,
+                    accessibility: accessibility,
+                    modifiers: modifiers,
+                    explicitInterfaceImplementations: useExplicitInterfaceSymbol ? ImmutableArray.Create(@event) : default,
+                    name: memberName,
+                    addMethod: GetAddOrRemoveMethod(@event, generateInvisibly, accessor, memberName, factory.AddEventHandler),
+                    removeMethod: GetAddOrRemoveMethod(@event, generateInvisibly, accessor, memberName, factory.RemoveEventHandler));
             }
 
-            private IMethodSymbol GetAddOrRemoveMethod(bool generateInvisibly,
-                                                       IMethodSymbol accessor,
-                                                       string memberName,
-                                                       Func<SyntaxNode, SyntaxNode, SyntaxNode> createAddOrRemoveHandler)
+            private IMethodSymbol GetAddOrRemoveMethod(
+                IEventSymbol @event, bool generateInvisibly, IMethodSymbol accessor, string memberName,
+                Func<SyntaxNode, SyntaxNode, SyntaxNode> createAddOrRemoveHandler)
             {
                 if (ThroughMember != null)
                 {
-                    var factory = Document.GetLanguageService<SyntaxGenerator>();
-                    var throughExpression = CreateThroughExpression(factory);
-                    var statement = factory.ExpressionStatement(createAddOrRemoveHandler(
-                        factory.MemberAccessExpression(throughExpression, memberName), factory.IdentifierName("value")));
+                    var generator = Document.GetRequiredLanguageService<SyntaxGenerator>();
+                    var throughExpression = generator.CreateDelegateThroughExpression(@event, ThroughMember);
+                    var statement = generator.ExpressionStatement(createAddOrRemoveHandler(
+                        generator.MemberAccessExpression(throughExpression, memberName), generator.IdentifierName("value")));
 
                     return CodeGenerationSymbolFactory.CreateAccessorSymbol(
                            attributes: default,
@@ -438,80 +428,6 @@ private static bool IsUnexpressibleTypeParameter(ITypeParameterSymbol typeParame
                 return generateInvisibly ? accessor : null;
             }
 
-            private SyntaxNode CreateThroughExpression(SyntaxGenerator generator)
-            {
-                var through = ThroughMember.IsStatic
-                        ? GenerateName(generator, State.ClassOrStructType.IsGenericType)
-                        : generator.ThisExpression();
-
-                through = generator.MemberAccessExpression(
-                    through, generator.IdentifierName(ThroughMember.Name));
-
-                var throughMemberType = ThroughMember.GetMemberType();
-                if ((State.InterfaceTypes != null) && (throughMemberType != null))
-                {
-                    // In the case of 'implement interface through field / property' , we need to know what
-                    // interface we are implementing so that we can insert casts to this interface on every
-                    // usage of the field in the generated code. Without these casts we would end up generating
-                    // code that fails compilation in certain situations.
-                    // 
-                    // For example consider the following code.
-                    //      class C : IReadOnlyList<int> { int[] field; }
-                    // When applying the 'implement interface through field' code fix in the above example,
-                    // we need to generate the following code to implement the Count property on IReadOnlyList<int>
-                    //      class C : IReadOnlyList<int> { int[] field; int Count { get { ((IReadOnlyList<int>)field).Count; } ...}
-                    // as opposed to the following code which will fail to compile (because the array field
-                    // doesn't have a property named .Count) -
-                    //      class C : IReadOnlyList<int> { int[] field; int Count { get { field.Count; } ...}
-                    //
-                    // The 'InterfaceTypes' property on the state object always contains only one item
-                    // in the case of C# i.e. it will contain exactly the interface we are trying to implement.
-                    // This is also the case most of the time in the case of VB, except in certain error conditions
-                    // (recursive / circular cases) where the span of the squiggle for the corresponding 
-                    // diagnostic (BC30149) changes and 'InterfaceTypes' ends up including all interfaces
-                    // in the Implements clause. For the purposes of inserting the above cast, we ignore the
-                    // uncommon case and optimize for the common one - in other words, we only apply the cast
-                    // in cases where we can unambiguously figure out which interface we are trying to implement.
-                    var interfaceBeingImplemented = State.InterfaceTypes.SingleOrDefault();
-                    if (interfaceBeingImplemented != null)
-                    {
-                        if (!throughMemberType.Equals(interfaceBeingImplemented))
-                        {
-                            through = generator.CastExpression(interfaceBeingImplemented,
-                                through.WithAdditionalAnnotations(Simplifier.Annotation));
-                        }
-                        else if (!ThroughMember.IsStatic &&
-                            ThroughMember is IPropertySymbol throughMemberProperty &&
-                            throughMemberProperty.ExplicitInterfaceImplementations.Any())
-                        {
-                            // If we are implementing through an explicitly implemented property, we need to cast 'this' to
-                            // the explicitly implemented interface type before calling the member, as in:
-                            //       ((IA)this).Prop.Member();
-                            //
-                            var explicitlyImplementedProperty = throughMemberProperty.ExplicitInterfaceImplementations[0];
-
-                            var explicitImplementationCast = generator.CastExpression(
-                                explicitlyImplementedProperty.ContainingType,
-                                generator.ThisExpression());
-
-                            through = generator.MemberAccessExpression(explicitImplementationCast,
-                                generator.IdentifierName(explicitlyImplementedProperty.Name));
-
-                            through = through.WithAdditionalAnnotations(Simplifier.Annotation);
-                        }
-                    }
-                }
-
-                return through.WithAdditionalAnnotations(Simplifier.Annotation);
-            }
-
-            private SyntaxNode GenerateName(SyntaxGenerator factory, bool isGenericType)
-            {
-                return isGenericType
-                    ? factory.GenericName(State.ClassOrStructType.Name, State.ClassOrStructType.TypeArguments)
-                    : factory.IdentifierName(State.ClassOrStructType.Name);
-            }
-
             private bool HasNameConflict(
                 ISymbol member,
                 string memberName,

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.CodeAction_Method.cs

@@ -23,8 +23,7 @@ internal partial class ImplementInterfaceCodeAction
                 DeclarationModifiers modifiers,
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
-                string memberName,
-                CancellationToken cancellationToken)
+                string memberName)
             {
                 var syntaxFacts = Document.GetLanguageService<ISyntaxFactsService>();
 
@@ -46,37 +45,11 @@ internal partial class ImplementInterfaceCodeAction
             }
 
             private SyntaxNode CreateStatement(Compilation compilation, IMethodSymbol method)
-            {
-                if (ThroughMember == null)
-                {
-                    var factory = Document.GetLanguageService<SyntaxGenerator>();
-                    return factory.CreateThrowNotImplementedStatement(compilation);
-                }
-                else
-                {
-                    return CreateDelegationStatement(method);
-                }
-            }
-
-            private SyntaxNode CreateDelegationStatement(
-                IMethodSymbol method)
             {
                 var factory = Document.GetLanguageService<SyntaxGenerator>();
-                var through = CreateThroughExpression(factory);
-
-                var memberName = method.IsGenericMethod
-                    ? factory.GenericName(method.Name, method.TypeArguments.OfType<ITypeSymbol>().ToList())
-                    : factory.IdentifierName(method.Name);
-
-                through = factory.MemberAccessExpression(
-                    through, memberName);
-
-                var arguments = factory.CreateArguments(method.Parameters.As<IParameterSymbol>());
-                var invocationExpression = factory.InvocationExpression(through, arguments);
-
-                return method.ReturnsVoid
-                    ? factory.ExpressionStatement(invocationExpression)
-                    : factory.ReturnStatement(invocationExpression);
+                return ThroughMember == null
+                    ? factory.CreateThrowNotImplementedStatement(compilation)
+                    : factory.GenerateDelegateThroughMemberStatement(method, ThroughMember);
             }
         }
     }

src/Features/Core/Portable/ImplementInterface/AbstractImplementInterfaceService.CodeAction_Property.cs

@@ -38,11 +38,11 @@ internal partial class ImplementInterfaceCodeAction
 
                 var getAccessor = GenerateGetAccessor(
                     compilation, property, accessibility, generateAbstractly, useExplicitInterfaceSymbol,
-                    propertyGenerationBehavior, attributesToRemove, cancellationToken);
+                    propertyGenerationBehavior, attributesToRemove);
 
                 var setAccessor = GenerateSetAccessor(
                     compilation, property, accessibility, generateAbstractly, useExplicitInterfaceSymbol,
-                    propertyGenerationBehavior, attributesToRemove, cancellationToken);
+                    propertyGenerationBehavior, attributesToRemove);
 
                 var syntaxFacts = Document.Project.LanguageServices.GetRequiredService<ISyntaxFactsService>();
 
@@ -54,7 +54,6 @@ internal partial class ImplementInterfaceCodeAction
 
                 updatedProperty = updatedProperty.RemoveInaccessibleAttributesAndAttributesOfTypes(compilation.Assembly, attributesToRemove);
 
-                // TODO(cyrusn): Delegate through throughMember if it's non-null.
                 return CodeGenerationSymbolFactory.CreatePropertySymbol(
                     updatedProperty,
                     accessibility: accessibility,
@@ -84,8 +83,7 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
                 ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
-                INamedTypeSymbol[] attributesToRemove,
-                CancellationToken cancellationToken)
+                INamedTypeSymbol[] attributesToRemove)
             {
                 if (property.SetMethod == null)
                 {
@@ -118,8 +116,7 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 bool generateAbstractly,
                 bool useExplicitInterfaceSymbol,
                 ImplementTypePropertyGenerationBehavior propertyGenerationBehavior,
-                INamedTypeSymbol[] attributesToRemove,
-                CancellationToken cancellationToken)
+                INamedTypeSymbol[] attributesToRemove)
             {
                 if (property.GetMethod == null)
                 {
@@ -146,40 +143,11 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 ImplementTypePropertyGenerationBehavior propertyGenerationBehavior)
             {
                 if (generateAbstractly)
-                {
                     return default;
-                }
-
-                var factory = Document.Project.LanguageServices.GetRequiredService<SyntaxGenerator>();
-                if (ThroughMember != null)
-                {
-                    var throughExpression = CreateThroughExpression(factory);
-                    SyntaxNode expression;
-
-                    if (property.IsIndexer)
-                    {
-                        expression = throughExpression;
-                    }
-                    else
-                    {
-                        expression = factory.MemberAccessExpression(
-                                                throughExpression, factory.IdentifierName(property.Name));
-                    }
-
-                    if (property.Parameters.Length > 0)
-                    {
-                        var arguments = factory.CreateArguments(property.Parameters.As<IParameterSymbol>());
-                        expression = factory.ElementAccessExpression(expression, arguments);
-                    }
-
-                    expression = factory.AssignmentStatement(expression, factory.IdentifierName("value"));
-
-                    return ImmutableArray.Create(factory.ExpressionStatement(expression));
-                }
 
-                return propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties
-                    ? default
-                    : factory.CreateThrowNotImplementedStatementBlock(compilation);
+                var generator = Document.GetRequiredLanguageService<SyntaxGenerator>();
+                return generator.GetSetAccessorStatements(compilation, property, this.ThroughMember,
+                    propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties);
             }
 
             private ImmutableArray<SyntaxNode> GetGetAccessorStatements(
@@ -189,38 +157,11 @@ private INamedTypeSymbol[] AttributesToRemove(Compilation compilation)
                 ImplementTypePropertyGenerationBehavior propertyGenerationBehavior)
             {
                 if (generateAbstractly)
-                {
                     return default;
-                }
-
-                var factory = Document.Project.LanguageServices.GetRequiredService<SyntaxGenerator>();
-                if (ThroughMember != null)
-                {
-                    var throughExpression = CreateThroughExpression(factory);
-                    SyntaxNode expression;
-
-                    if (property.IsIndexer)
-                    {
-                        expression = throughExpression;
-                    }
-                    else
-                    {
-                        expression = factory.MemberAccessExpression(
-                                                throughExpression, factory.IdentifierName(property.Name));
-                    }
-
-                    if (property.Parameters.Length > 0)
-                    {
-                        var arguments = factory.CreateArguments(property.Parameters.As<IParameterSymbol>());
-                        expression = factory.ElementAccessExpression(expression, arguments);
-                    }
-
-                    return ImmutableArray.Create(factory.ReturnStatement(expression));
-                }
 
-                return propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties
-                    ? default
-                    : factory.CreateThrowNotImplementedStatementBlock(compilation);
+                var generator = Document.Project.LanguageServices.GetRequiredService<SyntaxGenerator>();
+                return generator.GetGetAccessorStatements(compilation, property, ThroughMember,
+                    propertyGenerationBehavior == ImplementTypePropertyGenerationBehavior.PreferAutoProperties);
             }
         }
     }

src/Features/Core/Portable/xlf/FeaturesResources.cs.xlf

@@ -277,16 +277,6 @@
         <target state="translated">Implementace GetHashCode se dá zjednodušit.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Implementovat všechna rozhraní explicitně</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Implementovat explicitně</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Implementovat rozhraní {0} explicitně</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Implementovat všechna rozhraní implicitně</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implementovat implicitně</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Odsadit všechny argumenty</target>

src/Features/Core/Portable/xlf/FeaturesResources.de.xlf

@@ -277,16 +277,6 @@
         <target state="translated">Die Implementierung von "GetHashCode" kann vereinfacht werden.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Alle Schnittstellen explizit implementieren</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Explizit implementieren</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">"{0}" explizit implementieren</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Alle Schnittstellen implizit implementieren</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implizit implementieren</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Alle Argumente einrücken</target>

src/Features/Core/Portable/xlf/FeaturesResources.es.xlf

@@ -277,16 +277,6 @@
         <target state="translated">La implementación de "GetHashCode" se puede simplificar.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Implementar todas las interfaces de forma explícita</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Implementar de forma explícita</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Implementar "{0}" de forma explícita</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Implementar todas las interfaces de forma implícita</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implementar de forma implícita</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Aplicar sangría a todos los argumentos</target>

src/Features/Core/Portable/xlf/FeaturesResources.fr.xlf

@@ -277,16 +277,6 @@
         <target state="translated">L'implémentation de 'GetHashCode' peut être simplifiée</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Implémenter toutes les interfaces explicitement</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Implémenter explicitement</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Implémenter '{0}' explicitement</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Implémenter toutes les interfaces implicitement</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implémenter implicitement</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Mettre en retrait tous les arguments</target>

src/Features/Core/Portable/xlf/FeaturesResources.it.xlf

@@ -277,16 +277,6 @@
         <target state="translated">L'implementazione di 'GetHashCode' può essere semplificata</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Implementa tutte le interfacce in modo esplicito</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Implementa in modo esplicito</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Implementa '{0}' in modo esplicito</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Implementa tutte le interfacce in modo implicito</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implementa in modo implicito</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Imposta rientro per tutti gli argomenti</target>

src/Features/Core/Portable/xlf/FeaturesResources.ja.xlf

@@ -277,16 +277,6 @@
         <target state="translated">'GetHashCode' の実装を簡略化できます</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">すべてのインターフェイスを明示的に実装する</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">明示的に実装する</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">'{0}' を明示的に実装する</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">すべてのインターフェイスを暗黙的に実装する</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">暗黙的に実装する</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">すべての引数にインデントを設定します</target>

src/Features/Core/Portable/xlf/FeaturesResources.ko.xlf

@@ -277,16 +277,6 @@
         <target state="translated">'GetHashCode' 구현이 간소화될 수 있습니다.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">모든 인터페이스를 명시적으로 구현</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">명시적으로 구현</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">'{0}'을(를) 명시적으로 구현</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">모든 인터페이스를 암시적으로 구현</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">암시적으로 구현</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">모든 인수 들여쓰기</target>

src/Features/Core/Portable/xlf/FeaturesResources.pl.xlf

@@ -277,16 +277,6 @@
         <target state="translated">Implementację „GetHashCode” można uprościć</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Jawnie zaimplementuj wszystkie interfejsy</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Zaimplementuj jawnie</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Jawnie zaimplementuj interfejs „{0}”</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Niejawnie zaimplementuj wszystkie interfejsy</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Zaimplementuj niejawnie</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Dodaj wcięcie dla wszystkich argumentów</target>

src/Features/Core/Portable/xlf/FeaturesResources.pt-BR.xlf

@@ -277,16 +277,6 @@
         <target state="translated">A implementação de 'GetHashCode' pode ser simplificada</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Implementar todas as interfaces explicitamente</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Implementar explicitamente</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Implementar '{0}' explicitamente</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Implementar todas as interfaces implicitamente</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Implementar implicitamente</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Recuar todos os argumentos</target>

src/Features/Core/Portable/xlf/FeaturesResources.ru.xlf

@@ -277,16 +277,6 @@
         <target state="translated">Реализацию "GetHashCode" можно упростить.</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Реализовать все интерфейсы явно</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Реализовать явно</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">Реализовать "{0}" явно</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Реализовать все интерфейсы неявно</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Реализовать неявно</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Добавить отступы для всех аргументов</target>

src/Features/Core/Portable/xlf/FeaturesResources.tr.xlf

@@ -277,16 +277,6 @@
         <target state="translated">'GetHashCode' uygulaması basitleştirilebilir</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">Tüm arabirimleri açıkça uygula</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">Açıkça uygula</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">'{0}' öğesini açıkça uygula</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">Tüm arabirimleri örtük olarak uygula</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">Örtük olarak uygula</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">Tüm bağımsız değişkenleri girintile</target>

src/Features/Core/Portable/xlf/FeaturesResources.zh-Hans.xlf

@@ -277,16 +277,6 @@
         <target state="translated">可简化 "GetHashCode" 实现</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">显式实现所有接口</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">显式实现</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">显式实现 "{0}"</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">隐式实现所有接口</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">隐式实现</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">缩进所有参数</target>

src/Features/Core/Portable/xlf/FeaturesResources.zh-Hant.xlf

@@ -277,16 +277,6 @@
         <target state="translated">'GetHashCode' 實作可簡化</target>
         <note />
       </trans-unit>
-      <trans-unit id="Implement all interfaces explicitly">
-        <source>Implement all interfaces explicitly</source>
-        <target state="translated">明確實作所有介面</target>
-        <note />
-      </trans-unit>
-      <trans-unit id="Implement explicitly">
-        <source>Implement explicitly</source>
-        <target state="translated">明確實作</target>
-        <note />
-      </trans-unit>
       <trans-unit id="Implement_0_explicitly">
         <source>Implement '{0}' explicitly</source>
         <target state="translated">明確實作 '{0}'</target>
@@ -302,16 +292,31 @@
         <target state="new">Implement abstract class</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_all_interfaces_explicitly">
+        <source>Implement all interfaces explicitly</source>
+        <target state="new">Implement all interfaces explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_all_interfaces_implicitly">
         <source>Implement all interfaces implicitly</source>
         <target state="translated">隱含實作所有介面</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_explicitly">
+        <source>Implement explicitly</source>
+        <target state="new">Implement explicitly</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Implement_implicitly">
         <source>Implement implicitly</source>
         <target state="translated">隱含實作</target>
         <note />
       </trans-unit>
+      <trans-unit id="Implement_through_0">
+        <source>Implement through '{0}'</source>
+        <target state="new">Implement through '{0}'</target>
+        <note />
+      </trans-unit>
       <trans-unit id="Indent_all_arguments">
         <source>Indent all arguments</source>
         <target state="translated">將所有引數縮排</target>

src/Workspaces/Core/Portable/Shared/Extensions/SyntaxGeneratorExtensions.cs

@@ -545,5 +545,155 @@ private static DeclarationModifiers GetOverrideModifiers(ISymbol symbol)
                         : ImmutableArray.Create(codeFactory.ReturnStatement(body)));
             }
         }
+
+        /// <summary>
+        /// Generates a call to a method *through* an existing field or property symbol.
+        /// </summary>
+        /// <returns></returns>
+        public static SyntaxNode GenerateDelegateThroughMemberStatement(
+            this SyntaxGenerator generator, IMethodSymbol method, ISymbol throughMember)
+        {
+            var through = CreateDelegateThroughExpression(generator, method, throughMember);
+
+            var memberName = method.IsGenericMethod
+                ? generator.GenericName(method.Name, method.TypeArguments)
+                : generator.IdentifierName(method.Name);
+
+            through = generator.MemberAccessExpression(through, memberName);
+
+            var arguments = generator.CreateArguments(method.Parameters.As<IParameterSymbol>());
+            var invocationExpression = generator.InvocationExpression(through, arguments);
+
+            return method.ReturnsVoid
+                ? generator.ExpressionStatement(invocationExpression)
+                : generator.ReturnStatement(invocationExpression);
+        }
+
+        public static SyntaxNode CreateDelegateThroughExpression(
+            this SyntaxGenerator generator, ISymbol member, ISymbol throughMember)
+        {
+            var through = throughMember.IsStatic
+                ? GenerateContainerName(generator, throughMember)
+                : generator.ThisExpression();
+
+            through = generator.MemberAccessExpression(
+                through, generator.IdentifierName(throughMember.Name));
+
+            var throughMemberType = throughMember.GetMemberType();
+            if (member.ContainingType.IsInterfaceType() && throughMemberType != null)
+            {
+                // In the case of 'implement interface through field / property', we need to know what
+                // interface we are implementing so that we can insert casts to this interface on every
+                // usage of the field in the generated code. Without these casts we would end up generating
+                // code that fails compilation in certain situations.
+                // 
+                // For example consider the following code.
+                //      class C : IReadOnlyList<int> { int[] field; }
+                // When applying the 'implement interface through field' code fix in the above example,
+                // we need to generate the following code to implement the Count property on IReadOnlyList<int>
+                //      class C : IReadOnlyList<int> { int[] field; int Count { get { ((IReadOnlyList<int>)field).Count; } ...}
+                // as opposed to the following code which will fail to compile (because the array field
+                // doesn't have a property named .Count) -
+                //      class C : IReadOnlyList<int> { int[] field; int Count { get { field.Count; } ...}
+                //
+                // The 'InterfaceTypes' property on the state object always contains only one item
+                // in the case of C# i.e. it will contain exactly the interface we are trying to implement.
+                // This is also the case most of the time in the case of VB, except in certain error conditions
+                // (recursive / circular cases) where the span of the squiggle for the corresponding 
+                // diagnostic (BC30149) changes and 'InterfaceTypes' ends up including all interfaces
+                // in the Implements clause. For the purposes of inserting the above cast, we ignore the
+                // uncommon case and optimize for the common one - in other words, we only apply the cast
+                // in cases where we can unambiguously figure out which interface we are trying to implement.
+                var interfaceBeingImplemented = member.ContainingType;
+                if (!throughMemberType.Equals(interfaceBeingImplemented))
+                {
+                    through = generator.CastExpression(interfaceBeingImplemented,
+                        through.WithAdditionalAnnotations(Simplifier.Annotation));
+                }
+                else if (!throughMember.IsStatic &&
+                    throughMember is IPropertySymbol throughMemberProperty &&
+                    throughMemberProperty.ExplicitInterfaceImplementations.Any())
+                {
+                    // If we are implementing through an explicitly implemented property, we need to cast 'this' to
+                    // the explicitly implemented interface type before calling the member, as in:
+                    //       ((IA)this).Prop.Member();
+                    //
+                    var explicitlyImplementedProperty = throughMemberProperty.ExplicitInterfaceImplementations[0];
+
+                    var explicitImplementationCast = generator.CastExpression(
+                        explicitlyImplementedProperty.ContainingType,
+                        generator.ThisExpression());
+
+                    through = generator.MemberAccessExpression(explicitImplementationCast,
+                        generator.IdentifierName(explicitlyImplementedProperty.Name));
+
+                    through = through.WithAdditionalAnnotations(Simplifier.Annotation);
+                }
+            }
+
+            return through.WithAdditionalAnnotations(Simplifier.Annotation);
+
+            // local functions
+
+            static SyntaxNode GenerateContainerName(SyntaxGenerator factory, ISymbol throughMember)
+            {
+                var classOrStructType = throughMember.ContainingType;
+                return classOrStructType.IsGenericType
+                    ? factory.GenericName(classOrStructType.Name, classOrStructType.TypeArguments)
+                    : factory.IdentifierName(classOrStructType.Name);
+            }
+        }
+
+        public static ImmutableArray<SyntaxNode> GetGetAccessorStatements(
+            this SyntaxGenerator generator, Compilation compilation,
+            IPropertySymbol property, ISymbol throughMember, bool preferAutoProperties)
+        {
+            if (throughMember != null)
+            {
+                var throughExpression = CreateDelegateThroughExpression(generator, property, throughMember);
+                var expression = property.IsIndexer
+                    ? throughExpression
+                    : generator.MemberAccessExpression(
+                        throughExpression, generator.IdentifierName(property.Name));
+
+                if (property.Parameters.Length > 0)
+                {
+                    var arguments = generator.CreateArguments(property.Parameters.As<IParameterSymbol>());
+                    expression = generator.ElementAccessExpression(expression, arguments);
+                }
+
+                return ImmutableArray.Create(generator.ReturnStatement(expression));
+            }
+
+            return preferAutoProperties ? default : generator.CreateThrowNotImplementedStatementBlock(compilation);
+        }
+
+        public static ImmutableArray<SyntaxNode> GetSetAccessorStatements(
+            this SyntaxGenerator generator, Compilation compilation,
+            IPropertySymbol property, ISymbol throughMember, bool preferAutoProperties)
+        {
+            if (throughMember != null)
+            {
+                var throughExpression = CreateDelegateThroughExpression(generator, property, throughMember);
+                var expression = property.IsIndexer
+                    ? throughExpression
+                    : generator.MemberAccessExpression(
+                        throughExpression, generator.IdentifierName(property.Name));
+
+                if (property.Parameters.Length > 0)
+                {
+                    var arguments = generator.CreateArguments(property.Parameters.As<IParameterSymbol>());
+                    expression = generator.ElementAccessExpression(expression, arguments);
+                }
+
+                expression = generator.AssignmentStatement(expression, generator.IdentifierName("value"));
+
+                return ImmutableArray.Create(generator.ExpressionStatement(expression));
+            }
+
+            return preferAutoProperties
+                ? default
+                : generator.CreateThrowNotImplementedStatementBlock(compilation);
+        }
     }
 }