Non-functional code fix improvements

vsintegration/src/FSharp.Editor/CodeFixes/AddInstanceMemberParameter.fs

@@ -29,4 +29,4 @@ type internal AddInstanceMemberParameterCodeFixProvider() =
                     Changes = [ TextChange(TextSpan(context.Span.Start, 0), "x.") ]
                 }
 
-            CancellableTask.singleton (Some codeFix)
+            CancellableTask.singleton (ValueSome codeFix)

vsintegration/src/FSharp.Editor/CodeFixes/AddMissingEqualsToTypeDefinition.fs

@@ -30,18 +30,18 @@ type internal AddMissingEqualsToTypeDefinitionCodeFixProvider() =
 
                 // this should eliminate 99.9% of germs
                 if not <| message.Contains "=" then
-                    return None
+                    return ValueNone
                 else
 
                     let! range = context.GetErrorRangeAsync()
                     let! parseResults = context.Document.GetFSharpParseResultsAsync(nameof AddMissingEqualsToTypeDefinitionCodeFixProvider)
 
                     if not <| parseResults.IsPositionWithinTypeDefinition range.Start then
-                        return None
+                        return ValueNone
 
                     else
                         return
-                            Some
+                            ValueSome
                                 {
                                     Name = CodeFix.AddMissingEqualsToTypeDefinition
                                     Message = title

vsintegration/src/FSharp.Editor/CodeFixes/AddMissingFunKeyword.fs

@@ -36,7 +36,7 @@ type internal AddMissingFunKeywordCodeFixProvider [<ImportingConstructor>] () =
                 let! textOfError = context.GetSquigglyTextAsync()
 
                 if textOfError <> "->" then
-                    return None
+                    return ValueNone
                 else
                     let! cancellationToken = CancellableTask.getCurrentCancellationToken ()
                     let document = context.Document
@@ -61,9 +61,10 @@ type internal AddMissingFunKeywordCodeFixProvider [<ImportingConstructor>] () =
                             strictIndentation,
                             cancellationToken
                         )
-                        |> Option.bind (fun intendedArgLexerSymbol ->
-                            RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, intendedArgLexerSymbol.Range))
-                        |> Option.map (fun intendedArgSpan ->
+                        |> ValueOption.ofOption
+                        |> ValueOption.map (fun intendedArgLexerSymbol ->
+                            RoslynHelpers.FSharpRangeToTextSpan(sourceText, intendedArgLexerSymbol.Range))
+                        |> ValueOption.map (fun intendedArgSpan ->
                             {
                                 Name = CodeFix.AddMissingFunKeyword
                                 Message = title

vsintegration/src/FSharp.Editor/CodeFixes/AddMissingRecToMutuallyRecFunctions.fs

@@ -54,9 +54,10 @@ type internal AddMissingRecToMutuallyRecFunctionsCodeFixProvider [<ImportingCons
                         strictIndentation,
                         cancellationToken
                     )
-                    |> Option.bind (fun funcLexerSymbol -> RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, funcLexerSymbol.Range))
-                    |> Option.map (fun funcNameSpan -> sourceText.GetSubText(funcNameSpan).ToString())
-                    |> Option.map (fun funcName ->
+                    |> ValueOption.ofOption
+                    |> ValueOption.map (fun funcLexerSymbol -> RoslynHelpers.FSharpRangeToTextSpan(sourceText, funcLexerSymbol.Range))
+                    |> ValueOption.map (fun funcNameSpan -> sourceText.GetSubText(funcNameSpan).ToString())
+                    |> ValueOption.map (fun funcName ->
                         {
                             Name = CodeFix.AddMissingRecToMutuallyRecFunctions
                             Message = String.Format(titleFormat, funcName)

vsintegration/src/FSharp.Editor/CodeFixes/AddNewKeywordToDisposableConstructorInvocation.fs

@@ -25,7 +25,7 @@ type internal AddNewKeywordCodeFixProvider() =
     interface IFSharpCodeFixProvider with
         member _.GetCodeFixIfAppliesAsync context =
             CancellableTask.singleton (
-                Some
+                ValueSome
                     {
                         Name = CodeFix.AddNewKeyword
                         Message = title

vsintegration/src/FSharp.Editor/CodeFixes/ChangePrefixNegationToInfixSubtraction.fs

@@ -37,10 +37,10 @@ type internal ChangePrefixNegationToInfixSubtractionCodeFixProvider() =
                 let pos = findNextNonWhitespacePos sourceText (context.Span.End + 1)
 
                 if sourceText[pos] <> '-' then
-                    return None
+                    return ValueNone
                 else
                     return
-                        Some
+                        ValueSome
                             {
                                 Name = CodeFix.ChangePrefixNegationToInfixSubtraction
                                 Message = title

vsintegration/src/FSharp.Editor/CodeFixes/ChangeRefCellDerefToNotExpression.fs

@@ -30,8 +30,9 @@ type internal ChangeRefCellDerefToNotExpressionCodeFixProvider [<ImportingConstr
 
                 return
                     parseResults.TryRangeOfRefCellDereferenceContainingPos errorRange.Start
-                    |> Option.bind (fun range -> RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, range))
-                    |> Option.map (fun span ->
+                    |> ValueOption.ofOption
+                    |> ValueOption.map (fun range -> RoslynHelpers.FSharpRangeToTextSpan(sourceText, range))
+                    |> ValueOption.map (fun span ->
                         {
                             Name = CodeFix.ChangeRefCellDerefToNotExpression
                             Message = title

vsintegration/src/FSharp.Editor/CodeFixes/ChangeToUpcast.fs

@@ -52,7 +52,7 @@ type internal ChangeToUpcastCodeFixProvider() =
                             Changes = changes
                         }
 
-                    return Some codeFix
+                    return ValueSome codeFix
                 else
-                    return None
+                    return ValueNone
             }

vsintegration/src/FSharp.Editor/CodeFixes/CodeFixHelpers.fs

@@ -15,8 +15,40 @@ open Microsoft.CodeAnalysis.CodeFixes
 open Microsoft.CodeAnalysis.CodeActions
 open Microsoft.VisualStudio.FSharp.Editor.Telemetry
 
+open FSharp.Compiler.Symbols
+open FSharp.Compiler.Syntax
+
 open CancellableTasks
 
+module internal UnusedCodeFixHelper =
+    let getUnusedSymbol textSpan (document: Document) (sourceText: SourceText) codeFixName =
+        let ident = sourceText.ToString textSpan
+
+        // Prefixing operators and backticked identifiers does not make sense.
+        // We have to use the additional check for backticks
+        if PrettyNaming.IsIdentifierName ident then
+            cancellableTask {
+                let! lexerSymbol =
+                    document.TryFindFSharpLexerSymbolAsync(textSpan.Start, SymbolLookupKind.Greedy, false, false, CodeFix.RenameUnusedValue)
+
+                let m = RoslynHelpers.TextSpanToFSharpRange(document.FilePath, textSpan, sourceText)
+
+                let lineText = (sourceText.Lines.GetLineFromPosition textSpan.Start).ToString()
+
+                let! _, checkResults = document.GetFSharpParseAndCheckResultsAsync codeFixName
+
+                return
+                    lexerSymbol
+                    |> Option.bind (fun symbol -> checkResults.GetSymbolUseAtLocation(m.StartLine, m.EndColumn, lineText, symbol.FullIsland))
+                    |> ValueOption.ofOption
+                    |> ValueOption.bind (fun symbolUse ->
+                        match symbolUse.Symbol with
+                        | :? FSharpMemberOrFunctionOrValue as func when func.IsValue -> ValueSome symbolUse.Symbol
+                        | _ -> ValueNone)
+            }
+        else
+            CancellableTask.singleton ValueNone
+
 [<RequireQualifiedAccess>]
 module internal CodeFixHelpers =
     let reportCodeFixTelemetry
@@ -86,8 +118,8 @@ module internal CodeFixExtensions =
         member ctx.RegisterFsharpFix(codeFix: IFSharpCodeFixProvider) =
             cancellableTask {
                 match! codeFix.GetCodeFixIfAppliesAsync ctx with
-                | Some codeFix -> ctx.RegisterFsharpFix(codeFix.Name, codeFix.Message, codeFix.Changes)
-                | None -> ()
+                | ValueSome codeFix -> ctx.RegisterFsharpFix(codeFix.Name, codeFix.Message, codeFix.Changes)
+                | ValueNone -> ()
             }
             |> CancellableTask.startAsTask ctx.CancellationToken
 
@@ -140,7 +172,7 @@ module IFSharpCodeFixProviderExtensions =
                     |> Seq.map (fun task -> task token)
                     |> Task.WhenAll
 
-                let codeFixes = codeFixOpts |> Seq.choose id
+                let codeFixes = codeFixOpts |> Seq.map ValueOption.toOption |> Seq.choose id
                 let changes = codeFixes |> Seq.collect (fun codeFix -> codeFix.Changes)
                 let updatedDoc = doc.WithText(sourceText.WithChanges changes)
 

vsintegration/src/FSharp.Editor/CodeFixes/ConvertCSharpLambdaToFSharpLambda.fs

@@ -20,17 +20,12 @@ type internal ConvertCSharpLambdaToFSharpLambdaCodeFixProvider [<ImportingConstr
     static let title = SR.UseFSharpLambda()
 
     let tryGetSpans (parseResults: FSharpParseFileResults) (range: range) sourceText =
-        let flatten3 options =
-            match options with
-            | Some (Some a, Some b, Some c) -> Some(a, b, c)
-            | _ -> None
-
         parseResults.TryRangeOfParenEnclosingOpEqualsGreaterUsage range.Start
-        |> Option.map (fun (fullParenRange, lambdaArgRange, lambdaBodyRange) ->
-            RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, fullParenRange),
-            RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, lambdaArgRange),
-            RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, lambdaBodyRange))
-        |> flatten3
+        |> ValueOption.ofOption
+        |> ValueOption.map (fun (fullParenRange, lambdaArgRange, lambdaBodyRange) ->
+            RoslynHelpers.FSharpRangeToTextSpan(sourceText, fullParenRange),
+            RoslynHelpers.FSharpRangeToTextSpan(sourceText, lambdaArgRange),
+            RoslynHelpers.FSharpRangeToTextSpan(sourceText, lambdaBodyRange))
 
     override _.FixableDiagnosticIds = ImmutableArray.Create "FS0039"
 
@@ -47,7 +42,7 @@ type internal ConvertCSharpLambdaToFSharpLambdaCodeFixProvider [<ImportingConstr
 
                 return
                     tryGetSpans parseResults errorRange sourceText
-                    |> Option.map (fun (fullParenSpan, lambdaArgSpan, lambdaBodySpan) ->
+                    |> ValueOption.map (fun (fullParenSpan, lambdaArgSpan, lambdaBodySpan) ->
                         let replacement =
                             let argText = sourceText.GetSubText(lambdaArgSpan).ToString()
                             let bodyText = sourceText.GetSubText(lambdaBodySpan).ToString()

vsintegration/src/FSharp.Editor/CodeFixes/ConvertToAnonymousRecord.fs

@@ -29,8 +29,9 @@ type internal ConvertToAnonymousRecordCodeFixProvider [<ImportingConstructor>] (
 
                 return
                     parseResults.TryRangeOfRecordExpressionContainingPos errorRange.Start
-                    |> Option.bind (fun range -> RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, range))
-                    |> Option.map (fun span ->
+                    |> ValueOption.ofOption
+                    |> ValueOption.map (fun range -> RoslynHelpers.FSharpRangeToTextSpan(sourceText, range))
+                    |> ValueOption.map (fun span ->
                         {
                             Name = CodeFix.ConvertToAnonymousRecord
                             Message = title

vsintegration/src/FSharp.Editor/CodeFixes/ConvertToNotEqualsEqualityExpression.fs

@@ -26,10 +26,10 @@ type internal ConvertToNotEqualsEqualityExpressionCodeFixProvider() =
                 let! text = context.GetSquigglyTextAsync()
 
                 if text <> "!=" then
-                    return None
+                    return ValueNone
                 else
                     return
-                        Some
+                        ValueSome
                             {
                                 Name = CodeFix.ConvertToNotEqualsEqualityExpression
                                 Message = title

vsintegration/src/FSharp.Editor/CodeFixes/ConvertToSingleEqualsEqualityExpression.fs

@@ -26,10 +26,10 @@ type internal ConvertToSingleEqualsEqualityExpressionCodeFixProvider() =
                 let! text = context.GetSquigglyTextAsync()
 
                 if text <> "==" then
-                    return None
+                    return ValueNone
                 else
                     return
-                        Some
+                        ValueSome
                             {
                                 Name = CodeFix.ConvertToSingleEqualsEqualityExpression
                                 Message = title

vsintegration/src/FSharp.Editor/CodeFixes/DiscardUnusedValue.fs

@@ -0,0 +1,53 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace Microsoft.VisualStudio.FSharp.Editor
+
+open System
+open System.Composition
+open System.Threading.Tasks
+open System.Collections.Immutable
+
+open Microsoft.CodeAnalysis.Text
+open Microsoft.CodeAnalysis.CodeFixes
+
+open FSharp.Compiler.Symbols
+
+open CancellableTasks
+
+[<ExportCodeFixProvider(FSharpConstants.FSharpLanguageName, Name = CodeFix.RenameUnusedValue); Shared>]
+type internal RenameUnusedValueWithUnderscoreCodeFixProvider [<ImportingConstructor>] () =
+
+    inherit CodeFixProvider()
+
+    static let getTitle (symbolName: string) =
+        String.Format(SR.RenameValueToUnderscore(), symbolName)
+
+    override _.FixableDiagnosticIds = ImmutableArray.Create "FS1182"
+
+    override this.RegisterCodeFixesAsync context =
+        if context.Document.Project.IsFSharpCodeFixesUnusedDeclarationsEnabled then
+            context.RegisterFsharpFix this
+        else
+            Task.CompletedTask
+
+    override this.GetFixAllProvider() = this.RegisterFsharpFixAll()
+
+    interface IFSharpCodeFixProvider with
+        member _.GetCodeFixIfAppliesAsync context =
+            cancellableTask {
+                let! sourceText = context.GetSourceTextAsync()
+                let! symbol = UnusedCodeFixHelper.getUnusedSymbol context.Span context.Document sourceText CodeFix.RenameUnusedValue
+
+                return
+                    symbol
+                    |> ValueOption.filter (fun symbol ->
+                        match symbol with
+                        | :? FSharpMemberOrFunctionOrValue as x when x.IsConstructorThisValue -> false
+                        | _ -> true)
+                    |> ValueOption.map (fun symbol ->
+                        {
+                            Name = CodeFix.RenameUnusedValue
+                            Message = getTitle symbol.DisplayName
+                            Changes = [ TextChange(context.Span, "_") ]
+                        })
+            }

vsintegration/src/FSharp.Editor/CodeFixes/FixIndexerAccess.fs

@@ -28,7 +28,7 @@ type internal RemoveDotFromIndexerAccessOptInCodeFixProvider() =
     interface IFSharpCodeFixProvider with
         member _.GetCodeFixIfAppliesAsync context =
             CancellableTask.singleton (
-                Some
+                ValueSome
                     {
                         Name = CodeFix.RemoveIndexerDotBeforeBracket
                         Message = title

vsintegration/src/FSharp.Editor/CodeFixes/IFSharpCodeFix.fs

@@ -15,4 +15,4 @@ type FSharpCodeFix =
     }
 
 type IFSharpCodeFixProvider =
-    abstract member GetCodeFixIfAppliesAsync: context: CodeFixContext -> CancellableTask<FSharpCodeFix option>
+    abstract member GetCodeFixIfAppliesAsync: context: CodeFixContext -> CancellableTask<FSharpCodeFix voption>

vsintegration/src/FSharp.Editor/CodeFixes/MakeOuterBindingRecursive.fs

@@ -27,16 +27,17 @@ type internal MakeOuterBindingRecursiveCodeFixProvider [<ImportingConstructor>]
                 let! diagnosticRange = context.GetErrorRangeAsync()
 
                 if not <| parseResults.IsPosContainedInApplication diagnosticRange.Start then
-                    return None
+                    return ValueNone
                 else
                     return
                         parseResults.TryRangeOfNameOfNearestOuterBindingContainingPos diagnosticRange.Start
-                        |> Option.bind (fun bindingRange -> RoslynHelpers.TryFSharpRangeToTextSpan(sourceText, bindingRange))
-                        |> Option.filter (fun bindingSpan ->
+                        |> ValueOption.ofOption
+                        |> ValueOption.map (fun bindingRange -> RoslynHelpers.FSharpRangeToTextSpan(sourceText, bindingRange))
+                        |> ValueOption.filter (fun bindingSpan ->
                             sourceText
                                 .GetSubText(bindingSpan)
                                 .ContentEquals(sourceText.GetSubText context.Span))
-                        |> Option.map (fun bindingSpan ->
+                        |> ValueOption.map (fun bindingSpan ->
                             let title =
                                 String.Format(SR.MakeOuterBindingRecursive(), sourceText.GetSubText(bindingSpan).ToString())
 

vsintegration/src/FSharp.Editor/CodeFixes/PrefixUnusedValue.fs

@@ -0,0 +1,47 @@
+// Copyright (c) Microsoft Corporation.  All Rights Reserved.  See License.txt in the project root for license information.
+
+namespace Microsoft.VisualStudio.FSharp.Editor
+
+open System
+open System.Composition
+open System.Threading.Tasks
+open System.Collections.Immutable
+
+open Microsoft.CodeAnalysis.Text
+open Microsoft.CodeAnalysis.CodeFixes
+
+open CancellableTasks
+
+[<ExportCodeFixProvider(FSharpConstants.FSharpLanguageName, Name = CodeFix.PrefixUnusedValue); Shared>]
+type internal PrefixUnusedValueWithUnderscoreCodeFixProvider [<ImportingConstructor>] () =
+
+    inherit CodeFixProvider()
+
+    static let getTitle (symbolName: string) =
+        String.Format(SR.PrefixValueNameWithUnderscore(), symbolName)
+
+    override _.FixableDiagnosticIds = ImmutableArray.Create "FS1182"
+
+    override this.RegisterCodeFixesAsync context =
+        if context.Document.Project.IsFSharpCodeFixesUnusedDeclarationsEnabled then
+            context.RegisterFsharpFix this
+        else
+            Task.CompletedTask
+
+    override this.GetFixAllProvider() = this.RegisterFsharpFixAll()
+
+    interface IFSharpCodeFixProvider with
+        member _.GetCodeFixIfAppliesAsync context =
+            cancellableTask {
+                let! sourceText = context.GetSourceTextAsync()
+                let! symbol = UnusedCodeFixHelper.getUnusedSymbol context.Span context.Document sourceText CodeFix.PrefixUnusedValue
+
+                return
+                    symbol
+                    |> ValueOption.map (fun symbol ->
+                        {
+                            Name = CodeFix.PrefixUnusedValue
+                            Message = getTitle symbol.DisplayName
+                            Changes = [ TextChange(TextSpan(context.Span.Start, 0), "_") ]
+                        })
+            }

vsintegration/src/FSharp.Editor/CodeFixes/ProposeUppercaseLabel.fs

@@ -29,15 +29,15 @@ type internal ProposeUppercaseLabelCodeFixProvider [<ImportingConstructor>] () =
                 // probably not the 100% robust way to do that
                 // but actually we could also just implement the code fix for this case as well
                 if errorText.StartsWith "exception " then
-                    return None
+                    return ValueNone
                 else
                     let upperCased = string (Char.ToUpper errorText[0]) + errorText.Substring(1)
 
                     let title =
                         CompilerDiagnostics.GetErrorMessage(FSharpDiagnosticKind.ReplaceWithSuggestion upperCased)
 
                     return
-                        (Some
+                        (ValueSome
                             {
                                 Name = CodeFix.ProposeUppercaseLabel
                                 Message = title