Address review comments

src/Compilers/CSharp/Portable/Operations/CSharpArgument.cs

@@ -5,7 +5,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp
 {
-    internal abstract class BaseCSharpArgument : BaseArgument, IArgument
+    internal abstract class BaseCSharpArgument : BaseArgument
     {
         public BaseCSharpArgument(ArgumentKind argumentKind, IParameterSymbol parameter, SemanticModel semanticModel, SyntaxNode syntax, ITypeSymbol type, Optional<object> constantValue) :
             base(argumentKind, parameter, semanticModel, syntax, type, constantValue)

src/Compilers/VisualBasic/Portable/Operations/VisualBasicArgument.vb

@@ -19,13 +19,13 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
 
         Public Overrides ReadOnly Property InConversion As [Optional](Of CommonConversion)
             Get
-                Return If(InConversionInternal = Nothing, New [Optional](Of CommonConversion)(), InConversionInternal.ToCommonConversion())
+                Return If(InConversionInternal.Exists, InConversionInternal.ToCommonConversion(), New [Optional](Of CommonConversion)())
             End Get
         End Property
 
         Public Overrides ReadOnly Property OutConversion As [Optional](Of CommonConversion)
             Get
-                Return If(OutConversionInternal = Nothing, New [Optional](Of CommonConversion)(), OutConversionInternal.ToCommonConversion())
+                Return If(OutConversionInternal.Exists, OutConversionInternal.ToCommonConversion(), New [Optional](Of CommonConversion)())
             End Get
         End Property
     End Class

src/Compilers/VisualBasic/Portable/Operations/VisualBasicOperationFactory_Methods.vb

@@ -74,11 +74,12 @@ Namespace Microsoft.CodeAnalysis.Semantics
         Private Function CreateConversion(expression As BoundExpression) As Conversion
             If expression.Kind = BoundKind.Conversion Then
                 Dim conversion = DirectCast(expression, BoundConversion)
+                Dim conversionKind = conversion.ConversionKind
                 Dim method As MethodSymbol = Nothing
-                If conversion.Operand.Kind = BoundKind.UserDefinedConversion Then
+                If conversionKind.HasFlag(VisualBasic.ConversionKind.UserDefined) AndAlso conversion.Operand.Kind = BoundKind.UserDefinedConversion Then
                     method = DirectCast(conversion.Operand, BoundUserDefinedConversion).Call.Method
                 End If
-                Return New Conversion(KeyValuePair.Create(conversion.ConversionKind, method))
+                Return New Conversion(KeyValuePair.Create(conversionKind, method))
             End If
             Return New Conversion(Nothing) 'NoConversion
         End Function

src/Compilers/VisualBasic/Portable/VisualBasicExtensions.vb

@@ -1384,7 +1384,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         ''' </summary>
         ''' <param name="argument">The argument to get original info from.</param>
         ''' <returns>The underlying <see cref="Conversion"/> of the InConversion.</returns>
-        ''' <exception cref="InvalidCastException">If the <see cref="IArgument"/> was not created from Visual Basic code.</exception>
+        ''' <exception cref="ArgumentException">If the <see cref="IArgument"/> was not created from Visual Basic code.</exception>
         <Extension>
         Public Function GetInConversion(argument As IArgument) As Conversion
             Dim basicArgument = TryCast(argument, BaseVisualBasicArgument)
@@ -1402,7 +1402,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic
         ''' </summary>
         ''' <param name="argument">The argument to get original info from.</param>
         ''' <returns>The underlying <see cref="Conversion"/> of the OutConversion.</returns>
-        ''' <exception cref="InvalidCastException">If the <see cref="IArgument"/> was not created from Visual Basic code.</exception>
+        ''' <exception cref="ArgumentException">If the <see cref="IArgument"/> was not created from Visual Basic code.</exception>
         <Extension>
         Public Function GetOutConversion(argument As IArgument) As Conversion
             Dim basicArgument = TryCast(argument, BaseVisualBasicArgument)

src/Compilers/VisualBasic/Test/Semantic/IOperation/IOperationTests_IArgument.vb

@@ -758,8 +758,6 @@ BC30272: 'y' is not a parameter of 'Public Sub M2(x As Integer)'.
             VerifyOperationTreeAndDiagnosticsForTest(Of InvocationExpressionSyntax)(source, expectedOperationTree, expectedDiagnostics)
         End Sub
 
-
-
         <CompilerTrait(CompilerFeature.IOperation)>
         <Fact>
         Public Sub InOutConversion()