Merge pull request #18829 from rchande/fix18006

Include generic interfaces in implements clause completion

src/EditorFeatures/VisualBasicTest/Completion/CompletionProviders/ImplementsClauseCompletionProviderTests.vb

@@ -739,5 +739,60 @@ Class B
 
             Await VerifyNoItemsExistAsync(text)
         End Function
+
+        <WorkItem(18006, "https://github.com/dotnet/roslyn/issues/18006")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function ShowGenericTypes() As Task
+            Dim text = <text>Interface I(Of T)
+    Sub Foo()
+End Interface
+
+Class B
+    Implements I(Of Integer)
+
+    Public Sub Foo() Implements $$
+
+   </text>.Value
+
+            Await VerifyItemExistsAsync(text, "I(Of Integer)")
+        End Function
+
+        <WorkItem(18006, "https://github.com/dotnet/roslyn/issues/18006")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function ShowGenericTypes2() As Task
+            Dim text = <text>Interface I(Of T)
+    Sub Foo()
+End Interface
+
+Class B(Of T)
+    Implements I(Of T)
+
+    Public Sub Foo() Implements $$
+    End Sub
+End Class
+
+   </text>.Value
+
+            Await VerifyItemExistsAsync(text, "I(Of T)")
+        End Function
+
+        <WorkItem(18006, "https://github.com/dotnet/roslyn/issues/18006")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Async Function ShowGenericTypes3() As Task
+            Dim text = <text>Interface I(Of T)
+    Sub Foo()
+End Interface
+
+Class B(Of T)
+    Implements I(Of Integer)
+
+    Public Sub Foo() Implements  
+    End Sub
+End Class
+
+   </text>.Value
+
+            Await VerifyItemExistsAsync(text, "I(Of T)")
+        End Function
     End Class
 End Namespace
\ No newline at end of file

src/Features/VisualBasic/Portable/Completion/CompletionProviders/ImplementsClauseCompletionProvider.vb

@@ -162,7 +162,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
             End If
 
             Dim interfaceWithUnimplementedMembers = containingType.GetAllUnimplementedMembersInThis(containingType.Interfaces, AddressOf interfaceMemberGetter, cancellationToken) _
-                                                .Where(Function(i) i.Item2.Any(Function(s) MatchesMemberKind(s, kind))) _
+                                                .Where(Function(i) i.Item2.Any(Function(interfaceOrContainer) MatchesMemberKind(interfaceOrContainer, kind))) _
                                                 .Select(Function(i) i.Item1)
 
             Dim interfacesAndContainers = New HashSet(Of ISymbol)(interfaceWithUnimplementedMembers)
@@ -170,9 +170,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Completion.Providers
                 AddAliasesAndContainers(i, interfacesAndContainers, node, semanticModel)
             Next
 
-            Dim symbols = semanticModel.LookupSymbols(position)
+            Dim symbols = New HashSet(Of ISymbol)(semanticModel.LookupSymbols(position))
+            Dim availableInterfacesAndContainers = interfacesAndContainers.Where(
+                Function(interfaceOrContainer) symbols.Contains(interfaceOrContainer.OriginalDefinition)).ToImmutableArray()
 
-            Dim result = TryAddGlobalTo(interfacesAndContainers.Intersect(symbols.ToArray()).ToImmutableArray())
+            Dim result = TryAddGlobalTo(availableInterfacesAndContainers)
 
             ' Even if there's not anything left to implement, we'll show the list of interfaces, 
             ' the global namespace, and the project root namespace (if any), as long as the class implements something.