VB: Don't offer IntroduceVar for Nothing Literals

This is VB side change for internal bug 909152, similar to commit
287c94ab for C#

src/EditorFeatures/VisualBasicTest/CodeActions/IntroduceVariable/IntroduceVariableTests.vb

@@ -794,11 +794,10 @@ index:=1)
         End Sub
 
         <WorkItem(543529)>
+        <WorkItem(909152)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsIntroduceVariable)>
         Public Sub TestInStatementlessConstructorParameter()
-            Test(
-NewLines("Class C1 \n Sub New(Optional ByRef x As String = [|Nothing|]) \n End Sub \n End Class"),
-NewLines("Class C1 \n Private Const {|Rename:P|} As String = Nothing \n Sub New(Optional ByRef x As String = P) \n End Sub \n End Class"))
+            TestMissing(NewLines("Class C1 \n Sub New(Optional ByRef x As String = [|Nothing|]) \n End Sub \n End Class"))
         End Sub
 
         <WorkItem(543650)>
@@ -910,12 +909,10 @@ NewLines("Module M \n Sub Main() \n Dim x = <[|x|]/> \n End Sub \n End Module"))
         End Sub
 
         <WorkItem(545262)>
+        <WorkItem(909152)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsIntroduceVariable)>
         Public Sub TestInTernaryConditional()
-            Test(
-NewLines("Module Program \n Sub Main(args As String()) \n Dim p As Object = Nothing \n Dim Obj1 = If(New With {.a = True}.a, p, [|Nothing|]) \n End Sub \n End Module"),
-NewLines("Module Program \n Sub Main(args As String()) \n Dim p As Object = Nothing \n Const {|Rename:P1|} As Object = Nothing \n Dim Obj1 = If(New With {.a = True}.a, p, P1) \n End Sub \n End Module"),
-index:=2)
+            TestMissing(NewLines("Module Program \n Sub Main(args As String()) \n Dim p As Object = Nothing \n Dim Obj1 = If(New With {.a = True}.a, p, [|Nothing|]) \n End Sub \n End Module"))
         End Sub
 
         <WorkItem(545316)>
@@ -1401,6 +1398,24 @@ End Module
             Test(code, expected, index:=3, compareTokens:=False)
         End Sub
 
+        <WorkItem(909152)>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsIntroduceVariable)>
+        Public Sub TestMissingOnNothingLiteral()
+            TestMissing(
+<File>
+Imports System
+Module Program
+    Sub Main(args As String())
+        Main([|Nothing|])
+        M(Nothing)
+    End Sub
+
+    Sub M(i As Integer)
+    End Sub
+End Module
+</File>)
+        End Sub
+
         <WorkItem(1065661)>
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsIntroduceVariable)>
         Public Sub TestIntroduceVariableTextDoesntSpanLines()

src/Features/CSharp/IntroduceVariable/CSharpIntroduceVariableService.cs

@@ -109,7 +109,7 @@ protected override bool CanIntroduceVariableFor(ExpressionSyntax expression)
             }
 
             // (b) For Null Literals, as AllOccurences could introduce semantic errors.
-            if (expression is LiteralExpressionSyntax && ((LiteralExpressionSyntax)expression).IsKind(SyntaxKind.NullLiteralExpression))
+            if (expression.IsKind(SyntaxKind.NullLiteralExpression))
             {
                 return false;
             }

src/Features/VisualBasic/IntroduceVariable/VisualBasicIntroduceVariableService.vb

@@ -77,6 +77,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.IntroduceVariable
                 Return False
             End If
 
+            ' For Nothing Literals, AllOccurences could introduce semantic errors.
+            If expression.IsKind(SyntaxKind.NothingLiteralExpression) Then
+                Return False
+            End If
+
             Return True
         End Function