Have goto def go to implemented interface members if on an implementation already

src/EditorFeatures/Core/EditorFeaturesResources.resx

@@ -938,4 +938,7 @@ Do you want to proceed?</value>
   <data name="Removal_of_document_not_supported" xml:space="preserve">
     <value>Removal of document not supported</value>
   </data>
-</root>
+  <data name="_0_implemented_members" xml:space="preserve">
+    <value>'{0}' implemented members</value>
+  </data>
+</root>
\ No newline at end of file

src/EditorFeatures/Core/GoToDefinition/AbstractGoToDefinitionService.cs

@@ -4,9 +4,11 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.Editor.FindUsages;
 using Microsoft.CodeAnalysis.Editor.Host;
 using Microsoft.CodeAnalysis.LanguageServices;
 using Microsoft.CodeAnalysis.Navigation;
@@ -52,9 +54,11 @@ public bool TryGoToDefinition(Document document, int position, CancellationToken
             var symbolService = document.GetLanguageService<IGoToDefinitionSymbolService>();
             var (symbol, _) = symbolService.GetSymbolAndBoundSpanAsync(document, position, includeType: true, cancellationToken).WaitAndGetResult(cancellationToken);
             if (symbol is null)
-            {
                 return false;
-            }
+
+            var remapped = TryRemapIfAlreadyOnDefinition(document, position, symbol, cancellationToken);
+            if (remapped)
+                return true;
 
             var isThirdPartyNavigationAllowed = IsThirdPartyNavigationAllowed(symbol, position, document, cancellationToken);
 
@@ -62,10 +66,47 @@ public bool TryGoToDefinition(Document document, int position, CancellationToken
                 document.Project,
                 _streamingPresenter.Value,
                 thirdPartyNavigationAllowed: isThirdPartyNavigationAllowed,
-                throwOnHiddenDefinition: true,
                 cancellationToken: cancellationToken);
         }
 
+        private bool TryRemapIfAlreadyOnDefinition(
+            Document document, int position, 
+            ISymbol symbol, CancellationToken cancellationToken)
+        {
+            var project = document.Project;
+            var solution = project.Solution;
+
+            // if the symbol only has a single source location, and we're already on it,
+            // try to see if there's a better symbol we could navigate to.
+            var sourceLocations = symbol.Locations.WhereAsArray(loc => loc.IsInSource);
+            if (sourceLocations.Length != 1)
+                return false;
+
+            var definitionLocation = sourceLocations[0];
+            if (!definitionLocation.SourceSpan.IntersectsWith(position))
+                return false;
+
+            var definitionTree = definitionLocation.SourceTree;
+            var definitionDocument = solution.GetDocument(definitionTree);
+            if (definitionDocument != document)
+                return false;
+
+            // Ok, found a match.  Look for better symbols we could show results for instead.
+            var interfaceImpls = symbol.ExplicitOrImplicitInterfaceImplementations();
+            if (interfaceImpls.Length == 0)
+                return false;
+
+            var definitions = interfaceImpls.SelectMany(
+                i => GoToDefinitionHelpers.GetDefinitions(
+                    i, project, thirdPartyNavigationAllowed: false, cancellationToken)).ToImmutableArray();
+
+            var title = string.Format(EditorFeaturesResources._0_implemented_members,
+                FindUsagesHelpers.GetDisplayName(symbol));
+
+            return _streamingPresenter.Value.TryNavigateToOrPresentItemsAsync(
+                solution.Workspace, title, definitions).WaitAndGetResult(cancellationToken);
+        }
+
         private static bool IsThirdPartyNavigationAllowed(ISymbol symbolToNavigateTo, int caretPosition, Document document, CancellationToken cancellationToken)
         {
             var syntaxRoot = document.GetSyntaxRootSynchronously(cancellationToken);

src/EditorFeatures/Core/GoToDefinition/GoToDefinitionHelpers.cs

@@ -99,8 +99,7 @@ internal static class GoToDefinitionHelpers
             Project project,
             IStreamingFindUsagesPresenter streamingPresenter,
             CancellationToken cancellationToken,
-            bool thirdPartyNavigationAllowed = true,
-            bool throwOnHiddenDefinition = false)
+            bool thirdPartyNavigationAllowed = true)
         {
             var definitions = GetDefinitions(symbol, project, thirdPartyNavigationAllowed, cancellationToken);
 

src/EditorFeatures/Core/xlf/EditorFeaturesResources.cs.xlf

@@ -402,6 +402,11 @@
         <target state="translated">Vyřeší se tento počet konfliktů: {0}.</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">Počet nevyřešených konfliktů: {0}</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.de.xlf

@@ -402,6 +402,11 @@
         <target state="translated">{0} Konflikt(e) werden gelöst</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} nicht lösbare Konflikt(s)</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.es.xlf

@@ -402,6 +402,11 @@
         <target state="translated">Se va(n) a resolver {0} conflicto(s)</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} conflicto(s) sin solución</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.fr.xlf

@@ -402,6 +402,11 @@
         <target state="translated">{0} conflit(s) seront résolus</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} conflit(s) ne pouvant pas être résolu(s)</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.it.xlf

@@ -402,6 +402,11 @@
         <target state="translated">Verranno risolti {0} conflitti</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} conflitti non risolti</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ja.xlf

@@ -402,6 +402,11 @@
         <target state="translated">{0} 個の競合が解決されます</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">未解決の競合 {0}</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ko.xlf

@@ -402,6 +402,11 @@
         <target state="translated">충돌 {0}개가 해결됩니다.</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">해결할 수 없는 충돌 {0}개</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pl.xlf

@@ -402,6 +402,11 @@
         <target state="translated">Następująca liczba konfliktów zostanie rozwiązana: {0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">Liczba nierozwiązanych konfliktów: {0}</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.pt-BR.xlf

@@ -402,6 +402,11 @@
         <target state="translated">{0} conflito(s) será(ão) resolvido(s)</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} conflito(s) não solucionável(is)</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.ru.xlf

@@ -402,6 +402,11 @@
         <target state="translated">Конфликтов будет разрешено: {0}</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} неразрешимые конфликты</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.tr.xlf

@@ -402,6 +402,11 @@
         <target state="translated">{0} çakışmaları çözümlenecek</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} çözümlenemeyen çakışma</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hans.xlf

@@ -402,6 +402,11 @@
         <target state="translated">将解决 {0} 个冲突</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">{0} 个无法解决的冲突</target>

src/EditorFeatures/Core/xlf/EditorFeaturesResources.zh-Hant.xlf

@@ -402,6 +402,11 @@
         <target state="translated">將解決 {0} 項衝突</target>
         <note />
       </trans-unit>
+      <trans-unit id="_0_implemented_members">
+        <source>'{0}' implemented members</source>
+        <target state="new">'{0}' implemented members</target>
+        <note />
+      </trans-unit>
       <trans-unit id="_0_unresolvable_conflict_s">
         <source>{0} unresolvable conflict(s)</source>
         <target state="translated">有 {0} 個未解決的衝突</target>

src/EditorFeatures/Test2/GoToDefinition/GoToDefinitionTests.vb

@@ -962,6 +962,75 @@ class C
             Test(workspace)
         End Sub
 
+        <WorkItem(41870, "https://github.com/dotnet/roslyn/issues/41870")>
+        <WpfFact, Trait(Traits.Feature, Traits.Features.GoToDefinition)>
+        Public Sub TestCSharpGoToImplementedInterfaceMemberFromImpl1()
+            Dim workspace =
+<Workspace>
+    <Project Language="C#" CommonReferences="true">
+        <Document>
+interface IFoo1 { void [|Bar|](); }
+
+class Foo : IFoo1
+{
+    public void $$Bar()
+    {
+
+    }
+}
+        </Document>
+    </Project>
+</Workspace>
+
+            Test(workspace)
+        End Sub
+
+        <WorkItem(41870, "https://github.com/dotnet/roslyn/issues/41870")>
+        <WpfFact, Trait(Traits.Feature, Traits.Features.GoToDefinition)>
+        Public Sub TestCSharpGoToImplementedInterfaceMemberFromImpl2()
+            Dim workspace =
+<Workspace>
+    <Project Language="C#" CommonReferences="true">
+        <Document>
+interface IFoo1 { void [|Bar|](); }
+
+class Foo : IFoo1
+{
+    void IFoo1.$$Bar()
+    {
+
+    }
+}
+        </Document>
+    </Project>
+</Workspace>
+
+            Test(workspace)
+        End Sub
+
+        <WorkItem(41870, "https://github.com/dotnet/roslyn/issues/41870")>
+        <WpfFact, Trait(Traits.Feature, Traits.Features.GoToDefinition)>
+        Public Sub TestCSharpGoToImplementedInterfaceMemberFromImpl3()
+            Dim workspace =
+<Workspace>
+    <Project Language="C#" CommonReferences="true">
+        <Document>
+interface IFoo1 { void [|Bar|](); }
+interface IFoo2 { void [|Bar|](); }
+
+class Foo : IFoo1, IFoo2
+{
+    public void $$Bar()
+    {
+
+    }
+}
+        </Document>
+    </Project>
+</Workspace>
+
+            Test(workspace)
+        End Sub
 #End Region
 
 #Region "CSharp TupleTests"

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/ISymbolExtensions.cs

@@ -106,6 +106,9 @@ public static ImmutableArray<ISymbol> ExplicitInterfaceImplementations(this ISym
 
         public static ImmutableArray<ISymbol> ExplicitOrImplicitInterfaceImplementations(this ISymbol symbol)
         {
+            if (symbol.Kind != SymbolKind.Method && symbol.Kind != SymbolKind.Property && symbol.Kind != SymbolKind.Event)
+                return ImmutableArray<ISymbol>.Empty;
+
             var containingType = symbol.ContainingType;
             var query = from iface in containingType.AllInterfaces
                         from interfaceMember in iface.GetMembers()