Update usage string for VBC and update checklist for new LangVersion

src/Compilers/CSharp/Portable/CSharpResources.resx

@@ -4467,7 +4467,7 @@ To remove the warning, you can use /reference instead (set the Embed Interop Typ
  /define:<symbol list>         Define conditional compilation symbol(s) (Short 
                                form: /d)
  /langversion:<string>         Specify language version mode: ISO-1, ISO-2, 3, 
-                               4, 5, 6, Default, or Latest
+                               4, 5, 6, 7, 7.1, Default, or Latest
 
                         - SECURITY -
  /delaysign[+|-]               Delay-sign the assembly using only the public 

src/Compilers/CSharp/Portable/Symbols/Tuples/TupleTypeSymbol.cs

@@ -55,9 +55,9 @@ internal sealed class TupleTypeSymbol : WrappedNamedTypeSymbol
         internal const string RestFieldName = "Rest";
 
         private TupleTypeSymbol(Location locationOpt, NamedTypeSymbol underlyingType, ImmutableArray<Location> elementLocations,
-            ImmutableArray<string> elementNames, ImmutableArray<TypeSymbol> elementTypes, ImmutableArray<bool> inferredNamesPositions)
+            ImmutableArray<string> elementNames, ImmutableArray<TypeSymbol> elementTypes, ImmutableArray<bool> errorPositions)
             : this(locationOpt == null ? ImmutableArray<Location>.Empty : ImmutableArray.Create(locationOpt),
-                  underlyingType, elementLocations, elementNames, elementTypes, inferredNamesPositions)
+                  underlyingType, elementLocations, elementNames, elementTypes, errorPositions)
         {
         }
 

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -1392,6 +1392,32 @@ public void LanguageVersion_TryParseDisplayString(string input, bool success, La
             LanguageVersionAdded_Canary();
         }
 
+        [Fact]
+        public void LanguageVersion_CommandLineUsage()
+        {
+            var expected = Enum.GetValues(typeof(LanguageVersion)).Cast<LanguageVersion>()
+                .Where(v => v != LanguageVersion.CSharp1 && v != LanguageVersion.CSharp2)
+                .Select(v => v.ToDisplayString());
+            string help = CSharpResources.IDS_CSCHelp;
+
+            var rangeStart = help.IndexOf("/langversion");
+            var rangeEnd = help.IndexOf("/delaysign");
+            Assert.True(rangeEnd > rangeStart);
+
+            string helpRange = help.Substring(rangeStart, rangeEnd - rangeStart).ToLowerInvariant();
+            var acceptableSurroundingChar = new[] { '\r', '\n', ',' , ' '};
+            foreach (var version in expected)
+            {
+                var foundIndex = helpRange.IndexOf(version);
+                Assert.True(foundIndex > 0, $"Missing version '{version}'");
+                Assert.True(Array.IndexOf(acceptableSurroundingChar, helpRange[foundIndex - 1]) >= 0);
+                Assert.True(Array.IndexOf(acceptableSurroundingChar, helpRange[foundIndex + version.Length]) >= 0);
+            }
+
+            // The canary check is a reminder that this test needs to be updated when a language version is added
+            LanguageVersionAdded_Canary();
+        }
+
         [Fact]
         [WorkItem(546961, "http://vstfdevdiv:8080/DevDiv2/DevDiv/_workitems/edit/546961")]
         public void Define()

src/Compilers/CSharp/Test/Emit/CodeGen/CodeGenTupleTest.cs

@@ -3838,7 +3838,8 @@ int M()
             var model = compilation.GetSemanticModel(tree);
             var nodes = tree.GetCompilationUnitRoot().DescendantNodes();
 
-            // PROTOTYPE(tuple-names) The type for int? was not picked up
+            // The type for int? was not picked up
+            // Follow-up issue: https://github.com/dotnet/roslyn/issues/19144
             var yTuple = nodes.OfType<TupleExpressionSyntax>().ElementAt(0);
             Assert.Equal("(? e, (System.Int32 e, System.Int32, System.Int32, System.Int32))",
                 model.GetTypeInfo(yTuple).Type.ToTestDisplayString());

src/Compilers/VisualBasic/Portable/Symbols/Tuples/TupleFieldSymbol.vb

@@ -13,15 +13,15 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
     Friend Class TupleFieldSymbol
         Inherits WrappedFieldSymbol
 
-        Protected _containingTuple As TupleTypeSymbol
+        Protected ReadOnly _containingTuple As TupleTypeSymbol
 
         ''' <summary>
         ''' If this field represents a tuple element with index X, the field contains
         '''  2X      if this field represents a Default-named element
         '''  2X + 1  if this field represents a Friendly-named element
         ''' Otherwise, (-1 - [index in members array]);
         ''' </summary>
-        Private _tupleElementIndex As Integer
+        Private ReadOnly _tupleElementIndex As Integer
 
         Public Overrides ReadOnly Property IsTupleField As Boolean
             Get
@@ -123,7 +123,7 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
     Friend Class TupleElementFieldSymbol
         Inherits TupleFieldSymbol
 
-        Private _locations As ImmutableArray(Of Location)
+        Private ReadOnly _locations As ImmutableArray(Of Location)
 
         ' default tuple elements like Item1 Or Item20 could be provided by the user or
         ' otherwise implicitly declared by compiler
@@ -209,8 +209,8 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.Symbols
     Friend NotInheritable Class TupleVirtualElementFieldSymbol
         Inherits TupleElementFieldSymbol
 
-        Private _name As String
-        Private _cannotUse As Boolean ' With LanguageVersion 15, we will produce named elements that should not be used
+        Private ReadOnly _name As String
+        Private ReadOnly _cannotUse As Boolean ' With LanguageVersion 15, we will produce named elements that should not be used
 
         Public Sub New(container As TupleTypeSymbol,
                        underlyingField As FieldSymbol,

src/Compilers/VisualBasic/Portable/VBResources.resx

@@ -5130,7 +5130,7 @@
                                   import_list:namespace,...
 /langversion:<number>             Specify language version: 
                                   9|9.0|10|10.0|11|11.0|12|12.0|14|14.0|15|
-                                  15.0|default|latest
+                                  15.0|15.3|default|latest
 /optionexplicit[+|-]              Require explicit declaration of variables.
 /optioninfer[+|-]                 Allow type inference of variables.
 /rootnamespace:<string>           Specifies the root Namespace for all type 

src/Compilers/VisualBasic/Test/CommandLine/CommandLineTests.vb

@@ -1616,14 +1616,17 @@ End Module").Path
         <Fact>
         Public Sub LanguageVersionAdded_Canary()
             ' When a new version is added, this test will break. This list must be checked:
+            ' - update the command-line error for bad /langver flag (<see cref="ERRID.IDS_VBCHelp"/>)
             ' - update the "UpgradeProject" codefixer
             ' - update the IDE drop-down for selecting Language Version
+            ' - update legacy project system to pass Language Version from MSBuild to IDE (see CVbcMSBuildHostObject::SetLanguageVersion)
             ' - update all the tests that call this canary
             ' - update the command-line documentation (CommandLine.md)
             AssertEx.SetEqual({"default", "9", "10", "11", "12", "14", "15", "15.3", "latest"},
                 System.Enum.GetValues(GetType(LanguageVersion)).Cast(Of LanguageVersion)().Select(Function(v) v.ToDisplayString()))
             ' For minor versions, the format should be "x.y", such as "15.3"
         End Sub
+
         <Fact>
         Public Sub LanguageVersion_GetErrorCode()
             Dim versions = System.Enum.GetValues(GetType(LanguageVersion)).
@@ -1693,6 +1696,29 @@ End Module").Path
             LanguageVersionAdded_Canary()
         End Sub
 
+        <Fact>
+        Public Sub LanguageVersion_CommandLineUsage()
+            Dim expected = [Enum].GetValues(GetType(LanguageVersion)).Cast(Of LanguageVersion)().Select(Function(v) v.ToDisplayString())
+            Dim help = VBResources.IDS_VBCHelp
+
+            Dim rangeStart = help.IndexOf("/langversion")
+            Dim rangeEnd = help.IndexOf("/optionexplicit")
+            Assert.True(rangeEnd > rangeStart)
+
+            Dim helpRange = help.Substring(rangeStart, rangeEnd - rangeStart).ToLowerInvariant()
+            Dim acceptableSurroundingChar = {CChar(vbCr), CChar(vbLf), "|"c, " "c}
+
+            For Each v In expected
+                Dim foundIndex = helpRange.IndexOf(v)
+                Assert.True(foundIndex > 0, $"Missing version '{v}'")
+                Assert.True(Array.IndexOf(acceptableSurroundingChar, helpRange(foundIndex - 1)) >= 0)
+                Assert.True(Array.IndexOf(acceptableSurroundingChar, helpRange(foundIndex + v.Length)) >= 0)
+            Next
+
+            ' The canary check is a reminder that this test needs to be updated when a language version is added
+            LanguageVersionAdded_Canary()
+        End Sub
+
         <Fact>
         Public Sub TestDefine()
             TestDefines({"/D:a=True,b=1", "a.vb"},