Ensure that Language Version support flows to Parser (#6891)

* update testing

* Ensure Lange Feature can be used from the parser

* remove comments on tests

* repair tests.fs

fcs/FSharp.Compiler.Service/FSharp.Compiler.Service.fsproj

@@ -78,6 +78,12 @@
     <Compile Include="$(FSharpSourcesRoot)/fsharp/sr.fs">
       <Link>ErrorText/sr.fs</Link>
     </Compile>
+    <Compile Include="$(FSharpSourcesRoot)/fsharp/LanguageFeatures.fsi">
+      <Link>Driver\LanguageFeatures.fsi</Link>
+    </Compile>
+    <Compile Include="$(FSharpSourcesRoot)/fsharp/LanguageFeatures.fs">
+      <Link>Driver\LanguageFeatures.fs</Link>
+    </Compile>
     <Compile Include="$(FSharpSourcesRoot)/utils/prim-lexing.fsi">
       <Link>LexYaccRuntime/prim-lexing.fsi</Link>
     </Compile>

src/fsharp/CompileOps.fs

@@ -28,6 +28,7 @@ open FSharp.Compiler.AttributeChecking
 open FSharp.Compiler.ConstraintSolver
 open FSharp.Compiler.DiagnosticMessage
 open FSharp.Compiler.ErrorLogger
+open FSharp.Compiler.Features
 open FSharp.Compiler.Import
 open FSharp.Compiler.Infos
 open FSharp.Compiler.Lexhelp
@@ -1735,7 +1736,7 @@ let CollectDiagnostic (implicitIncludeDir, showFullPaths, flattenErrors, errorSt
                     let os = System.Text.StringBuilder()
                     OutputPhasedDiagnostic os err flattenErrors suggestNames
                     errors.Add( Diagnostic.Short(isError, os.ToString()) )
-        
+
             relatedErrors |> List.iter OutputRelatedError
 
         match err with
@@ -1834,82 +1835,6 @@ let ComputeMakePathAbsolute implicitIncludeDir (path: string) =
     with 
         :? System.ArgumentException -> path  
 
-
-//------------------------------------------------------------------------------------------------------------------
-// Language version command line switch
-//------------------------------------------------------------------------------------------------------------------
-// Add your features to this List - in code use languageVersion.SupportsFeature(LanguageFeatures.yourFeature) 
-// a return value of false means your feature is not supported by the user's language selection
-// All new language features added from now on must be protected by this.
-// Note:
-//   *  The fslang design process will require a decision about feature name and whether it is required.
-//   *  When a feature is assigned a release language, we will scrub the code of feature references and apply
-//      the Release Language version.
-
-/// LanguageFeature enumeration
-[<RequireQualifiedAccess>]
-type LanguageFeature =
-    | LanguageVersion46 = 0
-    | LanguageVersion47 = 1
-    | Nullness = 1000
-    | ScriptingPackageManagement = 1001
-
-/// LanguageVersion management
-type LanguageVersion (specifiedVersion) =
-
-    // When we increment language versions here preview is higher than current RTM version
-    static let languageVersion46 = 4.6m
-    static let languageVersion47 = 4.7m
-
-    static let previewVersion = languageVersion47       // Language version when preview specified
-    static let defaultVersion = languageVersion46       // Language version when default specified
-    static let latestVersion = defaultVersion           // Language version when latest specified
-    static let latestMajorVersion = languageVersion46   // Language version when latestmajor specified
-
-    static let validOptions = [| "preview"; "default"; "latest"; "latestmajor" |]
-    static let languageVersions = set [| latestVersion |]
-
-    static let features = dict [|
-        // Add new LanguageVersions here ...
-        LanguageFeature.LanguageVersion47, 4.7m
-        LanguageFeature.LanguageVersion46, 4.6m
-        LanguageFeature.Nullness, previewVersion
-        LanguageFeature.ScriptingPackageManagement, previewVersion
-        // Add new LanguageFeatures here ...
-        |]
-
-    static let dumpAllowedValues () =
-        printfn "%s" (FSComp.SR.optsSupportedLangVersions())
-        for v in validOptions do printfn "%s" v
-        for v in languageVersions |> Seq.sort do
-            let label = if v = defaultVersion || v = latestVersion then "(Default)" else ""
-            printf "%M %s" v label
-        exit 0
-        0m
-
-    let specified =
-        match specifiedVersion with
-        | "?" -> dumpAllowedValues()
-        | "preview" -> previewVersion
-        | "default" -> latestVersion
-        | "latest" -> latestVersion
-        | "latestmajor" -> latestMajorVersion
-        | _ ->
-            let raiseError () = error(Error(FSComp.SR.optsUnrecognizedLanguageVersion specifiedVersion, rangeCmdArgs))
-            match Decimal.TryParse(specifiedVersion) with
-            | true, v ->
-                if languageVersions.Contains(v) then v
-                else raiseError (); 0m
-            | _ ->
-                raiseError ()
-                0m
-
-    /// Check if this feature is supported by the selected langversion
-    member __.SupportsFeature featureId =
-        match features.TryGetValue featureId with
-        | true, v -> v <= specified
-        | false, _ -> false
-
 //----------------------------------------------------------------------------
 // Configuration
 //----------------------------------------------------------------------------
@@ -3556,8 +3481,8 @@ let ParseOneInputFile (tcConfig: TcConfig, lexResourceManager, conditionalCompil
        if List.exists (Filename.checkSuffix lower) (FSharpSigFileSuffixes@FSharpImplFileSuffixes) then  
             if not(FileSystem.SafeExists filename) then
                 error(Error(FSComp.SR.buildCouldNotFindSourceFile filename, rangeStartup))
-            // bug 3155: if the file name is indirect, use a full path
-            let lexbuf = UnicodeLexing.UnicodeFileAsLexbuf(filename, tcConfig.inputCodePage, retryLocked) 
+            let isFeatureSupported featureId = tcConfig.langVersion.SupportsFeature featureId
+            let lexbuf = UnicodeLexing.UnicodeFileAsLexbuf(isFeatureSupported, filename, tcConfig.inputCodePage, retryLocked) 
             ParseOneInputLexbuf(tcConfig, lexResourceManager, conditionalCompilationDefines, lexbuf, filename, isLastCompiland, errorLogger)
        else error(Error(FSComp.SR.buildInvalidSourceFileExtension(SanitizeFileName filename tcConfig.implicitIncludeDir), rangeStartup))
     with e -> (* errorR(Failure("parse failed")); *) errorRecovery e rangeStartup; None 
@@ -5080,11 +5005,13 @@ module private ScriptPreprocessClosure =
             | CodeContext.CompilationAndEvaluation -> ["INTERACTIVE"]
             | CodeContext.Compilation -> ["COMPILED"]
             | CodeContext.Editing -> "EDITING" :: (if IsScript filename then ["INTERACTIVE"] else ["COMPILED"])
-        let lexbuf = UnicodeLexing.SourceTextAsLexbuf(sourceText) 
-
+
+        let isFeatureSupported featureId = tcConfig.langVersion.SupportsFeature featureId
+        let lexbuf = UnicodeLexing.SourceTextAsLexbuf(isFeatureSupported, sourceText) 
+
         let isLastCompiland = (IsScript filename), tcConfig.target.IsExe        // The root compiland is last in the list of compilands.
         ParseOneInputLexbuf (tcConfig, lexResourceManager, defines, lexbuf, filename, isLastCompiland, errorLogger) 
-          
+
     /// Create a TcConfig for load closure starting from a single .fsx file
     let CreateScriptTextTcConfig 
            (legacyReferenceResolver, defaultFSharpBinariesDir, 

src/fsharp/CompileOps.fsi

@@ -16,6 +16,7 @@ open FSharp.Compiler.TypeChecker
 open FSharp.Compiler.Range
 open FSharp.Compiler.Ast
 open FSharp.Compiler.ErrorLogger
+open FSharp.Compiler.Features
 open FSharp.Compiler.Tast
 open FSharp.Compiler.TcGlobals
 open FSharp.Compiler.Text
@@ -217,19 +218,6 @@ type ICompilationThread =
     /// Enqueue work to be done on a compilation thread.
     abstract EnqueueWork: (CompilationThreadToken -> unit) -> unit
 
-/// LanguageFeature enumeration
-[<RequireQualifiedAccess>]
-type LanguageFeature =
-    | LanguageVersion46 = 0
-    | LanguageVersion47 = 1
-    | Nullness = 1000
-    | ScriptingPackageManagement = 1001
-
-/// LanguageVersion management
-type LanguageVersion =
-    new: string -> LanguageVersion
-    member SupportsFeature: LanguageFeature-> bool
-
 [<RequireQualifiedAccess>]
 type CompilerTarget = 
     | WinExe 

src/fsharp/CompileOptions.fs

@@ -17,6 +17,7 @@ open FSharp.Compiler.TcGlobals
 open FSharp.Compiler.Tast
 open FSharp.Compiler.Tastops 
 open FSharp.Compiler.ErrorLogger
+open FSharp.Compiler.Features
 open FSharp.Compiler.Lib
 open FSharp.Compiler.Range
 open FSharp.Compiler.IlxGen
@@ -813,13 +814,27 @@ let codeGenerationFlags isFsi (tcConfigB: TcConfigBuilder) =
 //----------------------
 
 let defineSymbol tcConfigB s = tcConfigB.conditionalCompilationDefines <- s :: tcConfigB.conditionalCompilationDefines
-      
+
 let mlCompatibilityFlag (tcConfigB: TcConfigBuilder) = 
     CompilerOption
        ("mlcompatibility", tagNone,
         OptionUnit (fun () -> tcConfigB.mlCompatibility<-true; tcConfigB.TurnWarningOff(rangeCmdArgs, "62")), None,
         Some (FSComp.SR.optsMlcompatibility()))
 
+/// LanguageVersion management
+let setLanguageVersion (specifiedVersion) =
+
+    let languageVersion = new LanguageVersion(specifiedVersion)
+    let dumpAllowedValues () =
+        printfn "%s" (FSComp.SR.optsSupportedLangVersions())
+        for v in languageVersion.ValidOptions do printfn "%s" v
+        for v in languageVersion.ValidVersions do printfn "%s" v
+        exit 0
+
+    if specifiedVersion = "?" then dumpAllowedValues ()
+    if not (languageVersion.ContainsVersion specifiedVersion) then error(Error(FSComp.SR.optsUnrecognizedLanguageVersion specifiedVersion, rangeCmdArgs))
+    languageVersion
+
 let languageFlags tcConfigB =
     [
         // -langversion:?                Display the allowed values for language version
@@ -828,7 +843,7 @@ let languageFlags tcConfigB =
         //                               'latest' (latest version, including minor versions),
         //                               'preview' (features for preview)
         //                               or specific versions like '4.7'
-        CompilerOption("langversion", tagLangVersionValues, OptionString (fun switch -> tcConfigB.langVersion <- LanguageVersion(switch)), None, Some (FSComp.SR.optsLangVersion()))
+        CompilerOption("langversion", tagLangVersionValues, OptionString (fun switch -> tcConfigB.langVersion <- setLanguageVersion(switch)), None, Some (FSComp.SR.optsLangVersion()))
 
         CompilerOption("checked", tagNone, OptionSwitch (fun switch -> tcConfigB.checkOverflow <- (switch = OptionSwitch.On)), None, Some (FSComp.SR.optsChecked()))
         CompilerOption("define", tagString, OptionString (defineSymbol tcConfigB), None, Some (FSComp.SR.optsDefine()))

src/fsharp/FSComp.txt

@@ -421,6 +421,7 @@ parsAttributesMustComeBeforeVal,"Attributes should be placed before 'val'"
 568,parsAllEnumFieldsRequireValues,"All enum fields must be given values"
 569,parsInlineAssemblyCannotHaveVisibilityDeclarations,"Accessibility modifiers are not permitted on inline assembly code types"
 571,parsUnexpectedIdentifier,"Unexpected identifier: '%s'"
+10,parsUnexpectedSymbolDot,"Unexpected symbol '.' in member definition. Expected 'with', '=' or other token."
 572,parsUnionCasesCannotHaveVisibilityDeclarations,"Accessibility modifiers are not permitted on union cases. Use 'type U = internal ...' or 'type U = private ...' to give an accessibility to the whole representation."
 573,parsEnumFieldsCannotHaveVisibilityDeclarations,"Accessibility modifiers are not permitted on enumeration fields"
 parsConsiderUsingSeparateRecordType,"Consider using a separate record type instead"

src/fsharp/FSharp.Build/Fsc.fs

@@ -108,7 +108,7 @@ type public Fsc () as this =
             for item in embeddedFiles do
                 builder.AppendSwitchIfNotNull("--embed:", item.ItemSpec)
         builder.AppendSwitchIfNotNull("--sourcelink:", sourceLink)
-        builder.AppendSwitchIfNotNull("--langVersion:", langVersion)
+        builder.AppendSwitchIfNotNull("--langversion:", langVersion)
         // NoFramework
         if noFramework then
             builder.AppendSwitch("--noframework")

src/fsharp/FSharp.Compiler.Private/FSharp.Compiler.Private.fsproj

@@ -86,6 +86,12 @@
     <Compile Include="..\sr.fs">
       <Link>ErrorText\sr.fs</Link>
     </Compile>
+    <Compile Include="..\LanguageFeatures.fsi">
+      <Link>Driver\LanguageFeatures.fsi</Link>
+    </Compile>
+    <Compile Include="..\LanguageFeatures.fs">
+      <Link>Driver\LanguageFeatures.fs</Link>
+    </Compile>
     <Compile Include="..\..\utils\prim-lexing.fsi">
       <Link>LexYaccRuntime\prim-lexing.fsi</Link>
     </Compile>

src/fsharp/LanguageFeatures.fs

@@ -0,0 +1,90 @@
+// Copyright (c) Microsoft Corporation. All Rights Reserved. See License.txt in the project root for license information.
+
+/// Coordinating compiler operations - configuration, loading initial context, reporting errors etc.
+module internal FSharp.Compiler.Features
+
+open System
+
+//------------------------------------------------------------------------------------------------------------------
+// Language version command line switch
+//------------------------------------------------------------------------------------------------------------------
+// Add your features to this List - in code use languageVersion.SupportsFeature(LanguageFeatures.yourFeature) 
+// a return value of false means your feature is not supported by the user's language selection
+// All new language features added from now on must be protected by this.
+// Note:
+//   *  The fslang design process will require a decision about feature name and whether it is required.
+//   *  When a feature is assigned a release language, we will scrub the code of feature references and apply
+//      the Release Language version.
+
+/// LanguageFeature enumeration
+[<RequireQualifiedAccess>]
+type LanguageFeature =
+    | LanguageVersion46 = 0
+    | LanguageVersion47 = 1
+    | SingleUnderscorePattern = 2
+    | Nullness = 1000
+    | ScriptingPackageManagement = 1001
+
+/// LanguageVersion management
+type LanguageVersion (specifiedVersion) =
+
+    // When we increment language versions here preview is higher than current RTM version
+    static let languageVersion46 = 4.6m
+    static let languageVersion47 = 4.7m
+
+    static let previewVersion = languageVersion47       // Language version when preview specified
+    static let defaultVersion = languageVersion46       // Language version when default specified
+    static let latestVersion = defaultVersion           // Language version when latest specified
+    static let latestMajorVersion = languageVersion46   // Language version when latestmajor specified
+
+    static let validOptions = [| "preview"; "default"; "latest"; "latestmajor" |]
+    static let languageVersions = set [| latestVersion |]
+
+    static let features = dict [|
+        // Add new LanguageVersions here ...
+        LanguageFeature.LanguageVersion47, 4.7m
+        LanguageFeature.LanguageVersion46, 4.6m
+        LanguageFeature.Nullness, previewVersion
+        LanguageFeature.ScriptingPackageManagement, previewVersion
+        LanguageFeature.SingleUnderscorePattern, previewVersion
+
+        // Add new LanguageFeatures here ...
+        |]
+
+    let specified =
+        match specifiedVersion with
+        | "?" -> 0m
+        | "preview" -> previewVersion
+        | "default" -> latestVersion
+        | "latest" -> latestVersion
+        | "latestmajor" -> latestMajorVersion
+        | _ ->
+            match Decimal.TryParse(specifiedVersion) with
+            | true, v -> v
+            | _ -> 0m
+
+    /// Check if this feature is supported by the selected langversion
+    member __.SupportsFeature featureId =
+        match features.TryGetValue featureId with
+        | true, v -> v <= specified
+        | false, _ -> false
+
+    /// Does the languageVersion support this version string
+    member __.ContainsVersion version =
+        match version with
+        | "?" | "preview" | "default" | "latest" | "latestmajor" -> true
+        | _ -> 
+            match Decimal.TryParse(specifiedVersion) with
+            | true, v -> languageVersions.Contains v
+            | _ -> false
+
+    /// Get a list of valid strings for help text
+    member __.ValidOptions = validOptions
+
+    /// Get a list of valid versions for help text
+    member __.ValidVersions = [|
+        for v in languageVersions |> Seq.sort do
+            let label = if v = defaultVersion || v = latestVersion then "(Default)" else ""
+            yield sprintf "%M %s" v label
+            |]
+

src/fsharp/LanguageFeatures.fsi

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+/// Coordinating compiler operations - configuration, loading initial context, reporting errors etc.
+module internal FSharp.Compiler.Features
+
+/// LanguageFeature enumeration
+[<RequireQualifiedAccess>]
+type LanguageFeature =
+    | LanguageVersion46 = 0
+    | LanguageVersion47 = 1
+    | SingleUnderscorePattern = 2
+    | Nullness = 1000
+    | ScriptingPackageManagement = 1001
+
+/// LanguageVersion management
+type LanguageVersion =
+
+    /// Create a LanguageVersion management object
+    new: string -> LanguageVersion
+
+    /// Get the list of valid versions
+    member ContainsVersion: string -> bool
+
+    /// Does the specified LanguageVersion support the specified feature
+    member SupportsFeature: LanguageFeature -> bool
+
+    /// Get the list of valid versions
+    member ValidVersions: string array
+
+    /// Get the list of valid options
+    member ValidOptions: string array