Making conditional access operators in VB not experimental.

***NO_CI***
 (changeset 1342366)

Src/Compilers/VisualBasic/Portable/Parser/ParseExpression.vb

@@ -387,7 +387,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax
                         ' This looks like ?. or ?! 
 
                         Dim qToken = DirectCast(start, PunctuationSyntax)
-                        AssertLanguageFeature(ERRID.FEATUREID_NullPropagatingOperator, qToken)
+                        qToken = AssertLanguageFeature(ERRID.FEATUREID_NullPropagatingOperator, qToken)
 
                         GetNextToken()
                         term = SyntaxFactory.ConditionalAccessExpression(term, qToken, ParsePostFixExpression(RedimOrNewParent, term:=Nothing))
@@ -453,7 +453,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax
                     ' This looks like ?. ?! or ?(
 
                     Dim qToken = DirectCast([Next], PunctuationSyntax)
-                    AssertLanguageFeature(ERRID.FEATUREID_NullPropagatingOperator, qToken)
 
                     GetNextToken()
 
@@ -481,11 +480,6 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax
         End Function
 
         Private Function CanStartConsequenceExpression(kind As SyntaxKind, qualified As Boolean) As Boolean
-
-            If _scanner.Options.LanguageVersion <> LanguageVersion.Experimental Then
-                Return False
-            End If
-
             Return kind = SyntaxKind.DotToken OrElse kind = SyntaxKind.ExclamationToken OrElse (qualified AndAlso kind = SyntaxKind.OpenParenToken)
         End Function
 

Src/Compilers/VisualBasic/Portable/Parser/ParseScan.vb

@@ -344,7 +344,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax
                 Not m_EvaluatingConditionCompilationExpression Then
 
                 If Not NextLineStartsWithStatementTerminator() Then
-                    If Not AssertLanguageFeature(ERRID.FEATUREID_LineContinuation, CurrentToken) Then
+                    If Not AssertLanguageFeature(ERRID.FEATUREID_LineContinuation) Then
                         Return False
                     End If
 

Src/Compilers/VisualBasic/Portable/Parser/Parser.vb

@@ -2395,7 +2395,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Syntax.InternalSyntax
         Private Function ParseObjectCollectionInitializer(fromKeyword As KeywordSyntax) As ObjectCollectionInitializerSyntax
             Debug.Assert(fromKeyword IsNot Nothing)
 
-            AssertLanguageFeature(ERRID.FEATUREID_CollectionInitializers, fromKeyword)
+            fromKeyword = AssertLanguageFeature(ERRID.FEATUREID_CollectionInitializers, fromKeyword)
 
             ' Allow implicit line continuation after FROM (dev10_508839) but only if followed by "{". 
             ' This is to avoid reporting an error at the beginning of then next line and then skipping the next statement.
@@ -4061,7 +4061,7 @@ checkNullable:
 
                 If CurrentToken.Kind = SyntaxKind.InKeyword Then
                     optionalVarianceModifier = DirectCast(CurrentToken, KeywordSyntax)
-                    AssertLanguageFeature(ERRID.FEATUREID_CoContraVariance, CurrentToken)
+                    optionalVarianceModifier = AssertLanguageFeature(ERRID.FEATUREID_CoContraVariance, optionalVarianceModifier)
                     GetNextToken()
 
                 Else
@@ -4079,7 +4079,7 @@ checkNullable:
                             name = id
                             optionalVarianceModifier = Nothing
                         Else
-                            AssertLanguageFeature(ERRID.FEATUREID_CoContraVariance, CurrentToken)
+                            outKeyword = AssertLanguageFeature(ERRID.FEATUREID_CoContraVariance, outKeyword)
                             optionalVarianceModifier = outKeyword
                         End If
                     End If
@@ -5790,15 +5790,28 @@ checkNullable:
             _currentToken = Nothing
         End Sub
 
-        ' .Parser::AssertLanguageFeature( [ unsigned feature ] [ _Inout_ Token* ErrorLocationToken ] )
+        ''' <summary>
+        ''' returns true if feature is available
+        ''' </summary>
         Private Function AssertLanguageFeature(
-            feature As ERRID,
-            ErrorLocationToken As SyntaxToken
+            feature As ERRID
         ) As Boolean
 
+            Return True
+        End Function
+
+        ''' <summary>
+        ''' Attaches an error to the node if feature is not available
+        ''' </summary>
+        Private Function AssertLanguageFeature(Of T As VisualBasicSyntaxNode)(
+            feature As ERRID,
+            node As T
+        ) As T
+
             ' If we are targeting the latest version of the compiler, all features are fair game
 
-            Return True
+            Return node
+
 #If MUSTCONVERT Then
      If m_CompilingLanguageVersion = LANGUAGE_CURRENT Then
                 Return True
@@ -5819,7 +5832,6 @@ checkNullable:
                 ReportSyntaxErrorForLanguageFeature(ERRID.ERR_LanguageVersion, ErrorLocationToken, feature, wszVersion)
             End If
 #End If
-            Return False
         End Function
 
         '============ Methods to test properties of NodeKind. ====================