VB side of do-not-simplify-nameof if it changes semantics.

src/EditorFeatures/VisualBasicTest/Diagnostics/SimplifyTypeNames/SimplifyTypeNamesTests.vb

@@ -120,6 +120,94 @@ Module Program
 End Module")
         End Function
 
+        <WorkItem(21449, "https://github.com/dotnet/roslyn/issues/21449")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsSimplifyTypeNames)>
+        Public Async Function DoNotChangeToAliasInNameOfIfItChangesNameOfName() As Task
+            Await TestInRegularAndScript1Async(
+"Imports System
+Imports Foo = SimplifyInsideNameof.Program
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof([|SimplifyInsideNameof.Program|]))
+    end sub
+  end class
+end namespace",
+"Imports System
+Imports Foo = SimplifyInsideNameof.Program
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof(Program))
+    end sub
+  end class
+end namespace")
+        End Function
+
+        <WorkItem(21449, "https://github.com/dotnet/roslyn/issues/21449")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsSimplifyTypeNames)>
+        Public Async Function DoChangeToAliasInNameOfIfItDoesNotAffectName1() As Task
+            Await TestInRegularAndScriptAsync(
+"Imports System
+Imports Goo = SimplifyInsideNameof.Program
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof([|SimplifyInsideNameof.Program|].Main))
+    end sub
+  end class
+end namespace",
+"Imports System
+Imports Goo = SimplifyInsideNameof.Program
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof(Goo.Main))
+    end sub
+  end class
+end namespace")
+        End Function
+
+        <WorkItem(21449, "https://github.com/dotnet/roslyn/issues/21449")>
+        <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsSimplifyTypeNames)>
+        Public Async Function DoChangeToAliasInNameOfIfItDoesNotAffectName2() As Task
+            Await TestInRegularAndScriptAsync(
+"Imports System
+Imports Goo = N.Goo
+
+namespace N
+    class Goo
+    end class
+end namespace
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof([|N.Goo|]))
+    end sub
+  end class
+end namespace",
+"Imports System
+Imports Goo = N.Goo
+
+namespace N
+    class Goo
+    end class
+end namespace
+
+namespace SimplifyInsideNameof
+  class Program
+    shared sub Main()
+      Console.WriteLine(nameof(Goo))
+    end sub
+  end class
+end namespace")
+        End Function
+
         <Fact, Trait(Traits.Feature, Traits.Features.CodeActionsSimplifyTypeNames)>
         Public Async Function TestWithCursorAtBeginning() As Task
             Await TestInRegularAndScriptAsync(

src/Workspaces/VisualBasic/Portable/Extensions/ExpressionSyntaxExtensions.vb

@@ -1761,6 +1761,21 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
         ' It's possible there is another symbol with the same name as the alias that binds first
         Private Function ValidateAliasForTarget(aliasReplacement As IAliasSymbol, semanticModel As SemanticModel, node As ExpressionSyntax, symbol As ISymbol) As Boolean
             Dim aliasName = aliasReplacement.Name
+
+            ' If we're the argument of a NameOf(X.Y) call, then we can't simplify to an
+            ' alias unless the alias has the same name as us (i.e. 'Y').
+            If node.IsNameOfArgumentExpression() Then
+                Dim nameofValueOpt = semanticModel.GetConstantValue(node.Parent.Parent.Parent)
+                If Not nameofValueOpt.HasValue Then
+                    Return False
+                End If
+
+                Dim existingValue = TryCast(nameofValueOpt.Value, String)
+                If existingValue Is Nothing OrElse existingValue <> aliasName Then
+                    Return False
+                End If
+            End If
+
             Dim boundSymbols = semanticModel.LookupNamespacesAndTypes(node.SpanStart, name:=aliasName)
             If boundSymbols.Length = 1 Then
                 Dim boundAlias = TryCast(boundSymbols(0), IAliasSymbol)
@@ -1776,6 +1791,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Extensions
             Return False
         End Function
 
+        <Extension>
+        Public Function IsNameOfArgumentExpression(expression As ExpressionSyntax) As Boolean
+            Return expression.IsParentKind(SyntaxKind.NameOfExpression)
+        End Function
+
         <Extension()>
         Private Function CanReplaceWithReducedName(
             name As NameSyntax,