Merge pull request #5554 from rchande/unlistdelegates

Unlist delegates from the VB completion list

Fixes https://github.com/dotnet/roslyn/issues/4208

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

@@ -6688,6 +6688,24 @@ Imports System
 Imports System.Collections.Generic
 Imports System.Linq
 
+Module Program
+    Sub Main(args As String())
+        Dim x = $$
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemIsAbsent(text, "Func(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemFuncExcludedInStatementContext()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
 Module Program
     Sub Main(args As String())
         $$
@@ -6784,6 +6802,129 @@ End Module
             VerifyItemExists(text, "Delegate")
         End Sub
 
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionExcludedInExpressionContext1()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Sub Main(args As String())
+        args.Select($$)
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemIsAbsent(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionExcludedInExpressionContext2()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Sub Main(args As String())
+        Dim x = $$
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemIsAbsent(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionExcludedInStatementContext()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Sub Main(args As String())
+        $$
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemIsAbsent(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionIncludedInGetType()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Sub Main(args As String())
+        GetType($$)
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemExists(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionIncludedInTypeOf()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Sub Main(args As String())
+        Dim s = TypeOf args Is $$
+    End Sub
+End Module
+]]></code>.Value
+            VerifyItemExists(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionIncludedInReturnTypeContext()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Function x() as $$
+    End Function
+End Module
+]]></code>.Value
+            VerifyItemExists(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
+        <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
+        <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
+        Public Sub SystemActionIncludedInFieldTypeContext()
+            Dim text =
+<code><![CDATA[
+Imports System
+Imports System.Collections.Generic
+Imports System.Linq
+
+Module Program
+    Dim x as $$
+End Module
+]]></code>.Value
+            VerifyItemExists(text, "Action(Of " & s_unicodeEllipsis & ")")
+        End Sub
+
         <WorkItem(4428, "https://github.com/dotnet/roslyn/issues/4428")>
         <Fact, Trait(Traits.Feature, Traits.Features.Completion)>
         Public Sub SystemDelegateInExpressionContext()

src/Workspaces/VisualBasic/Portable/Recommendations/VisualBasicRecommendationService.vb

@@ -138,24 +138,23 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Recommendations
             ' "Func(Of" tends to get in the way of typing "Function". Exclude System.Func from expression
             ' contexts, except within GetType
             If Not context.TargetToken.IsKind(SyntaxKind.OpenParenToken) OrElse
-               Not context.TargetToken.Parent.IsKind(SyntaxKind.GetTypeExpression) Then
+                    Not context.TargetToken.Parent.IsKind(SyntaxKind.GetTypeExpression) Then
 
-                symbols = symbols.Where(Function(s) Not IsSystemFunc(s))
+                symbols = symbols.Where(Function(s) Not IsInEligibleDelegate(s))
             End If
 
+
             ' Hide backing fields and events
             Return symbols.Where(Function(s) FilterEventsAndGeneratedSymbols(Nothing, s))
         End Function
 
-        Private Function IsSystemFunc(s As ISymbol) As Boolean
-            Dim namedTypeSymbol = TryCast(s, INamedTypeSymbol)
-            Return namedTypeSymbol IsNot Nothing AndAlso
-                    namedTypeSymbol.Name = "Func" AndAlso
-                    namedTypeSymbol.GetArity() > 0 AndAlso
-                    namedTypeSymbol.ContainingNamespace IsNot Nothing AndAlso
-                    namedTypeSymbol.ContainingNamespace.Name = "System" AndAlso
-                    namedTypeSymbol.ContainingNamespace.ContainingNamespace.IsGlobalNamespace
+        Private Function IsInEligibleDelegate(s As ISymbol) As Boolean
+            If s.IsDelegateType() Then
+                Dim typeSymbol = DirectCast(s, ITypeSymbol)
+                Return typeSymbol.SpecialType <> SpecialType.System_Delegate
+            End If
 
+            Return False
         End Function
 
         Private Function GetSymbolsForQualifiedNameSyntax(