[xperiandri]

Offers Ctrl+. on a member's optional parameter to switch it between option and voption (F# 10). defaultArg, Option functions and match cases on it in the body, and ?x = value arguments at call sites across the solution, are rewritten to match.

Not offered when a use of the parameter would change type (passed on, Option.map), for overrides, abstract slots and constructors, or when the file has a paired .fsi.

🤖 Generated with Claude Code

[github-actions]

✅ Release notes checked

---

✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
`vsintegration/src`	docs/release-notes/.VisualStudio/18.vNext.md

[T-Gro]

🤖🕵️ Please shorten the description using this guidance. Focus on the problem and why the change is needed, in simplified technical English. Leave the implementation inventory to the Files tab and retain necessary caveats.

[xperiandri]

Covered cases

Converts

• Parameter and body: member _.Greet(name: string, ?greeting: string) with defaultArg greeting "Hello" → [<Struct>] ?greeting: string with defaultValueArg greeting "Hello"
• Call sites in the same file: ?greeting = Some "Hey" → ?greeting = ValueSome "Hey", and ?greeting = g (with g: string option) → ?greeting = ValueOption.ofOption g; Greet("Ada") and greeting = "Hi" stay as they are
• Converting that whole file back gives back the original exactly (ValueSome "Hey" → Some "Hey", ValueOption.ofOption g → g)
• match on the parameter: | Some s -> s | None -> 1 → | ValueSome s -> s | ValueNone -> 1, both ways
• Option module functions, called directly or through a pipe, in a static member: Option.isSome step && step.IsSome then step |> Option.defaultValue 0 → ValueOption.isSome step && step.IsSome then step |> ValueOption.defaultValue 0 (IsSome unchanged), both ways
• Expression argument at a call site: ?step = (if true then step else None) → ?step = ValueOption.ofOption (if true then step else None), both ways
• A voption passed to a struct parameter, when converting back: ?step = step (with step: int voption) → ?step = ValueOption.toOption step
• Action titles: Use 'voption' for optional parameter / Use 'option' for optional parameter, exactly one action each
• Each converted document type-checks without errors

Not offered

• Parameter passed to a function the conversion does not handle: static member M(?x: int) = printfn "%A" x
• Option module function that is not supported: Option.map string x
• Override of an abstract slot: abstract M: ?x: int -> int with default _.M(?x) = defaultArg x 0
• Caret on the member name (M() instead of the parameter
• Parameter that is not optional: static member M(x: int option) = defaultArg x 0
• Before F# 10 (--langversion:9.0): static member M(?x: int) = defaultArg x 0
• File that has a signature file: static member M: ?x: int -> int

[github-actions]

🔍 Tooling Safety Check — Affects-Build-Infra
Affects-Build-Infra: Project files include new build inputs.

Generated by PR Tooling Safety Check · gpt56 718.9K · ◷

[Copilot]

Copilot review overview

🟡 Changes recommended

Several edge cases currently produce uncompilable, semantics-changing, or comment-losing edits.

Review effort: Balanced
Findings: 2 · 3 · 1

Open (6)

• Unqualified destination binding can resolve to user code · New
• Rewrites callers in projects lacking F# 10 support · New
• Misses explicitly targeted Struct attributes · New
• Renames functions when option argument is not final · New
• Generic calls are missed during call-site rewriting · New
• Conversion removes comments between function and argument · New

What changed in this PR

Adds an F# 10 IDE refactoring that converts optional member parameters between option and voption, updating compatible body usages and solution call sites.

Changes:

• Adds the conversion provider and safety checks.
• Adds tests, localized action resources, and project wiring.
• Documents the feature in Visual Studio release notes.

File	Description
vsintegration/​src/​FSharp.Editor/​Refactor/​ConvertOptionalParameterStruct.fs	Implements the refactoring.
vsintegration/​src/​FSharp.Editor/​FSharp.Editor.fsproj	Includes the provider.
vsintegration/​src/​FSharp.Editor/​FSharp.Editor.resx	Adds action titles.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.cs.xlf	Adds Czech resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.de.xlf	Adds German resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.es.xlf	Adds Spanish resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.fr.xlf	Adds French resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.it.xlf	Adds Italian resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.ja.xlf	Adds Japanese resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.ko.xlf	Adds Korean resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.pl.xlf	Adds Polish resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.pt-BR.xlf	Adds Portuguese resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.ru.xlf	Adds Russian resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.tr.xlf	Adds Turkish resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.zh-Hans.xlf	Adds Simplified Chinese resources.
vsintegration/​src/​FSharp.Editor/​xlf/​FSharp.Editor.zh-Hant.xlf	Adds Traditional Chinese resources.
vsintegration/​tests/​FSharp.Editor.Tests/​Refactors/​ConvertOptionalParameterStructTests.fs	Tests conversions and exclusions.
vsintegration/​tests/​FSharp.Editor.Tests/​FSharp.Editor.Tests.fsproj	Includes the tests.
docs/​release-notes/​.VisualStudio/​18.vNext.md	Documents the refactoring.

[xperiandri]

Fixed in eea18fa: every name the conversion writes (ValueSome/Some, ValueOption.*/Option.*, defaultValueArg/defaultArg) is now resolved at the place where it is written. If it can mean anything other than FSharp.Core there, the member body is not offered the conversion, and a call site keeps its value behind ValueOption.ofOption/toOption, written as Microsoft.FSharp.Core.ValueOption.… when that module is shadowed too. Tests: No action (local module ValueOption, local defaultValueArg) and Optional arguments at call sites follow the conversion.

[xperiandri]

Fixed in eea18fa: converting to a value option now needs F# 10 in the declaring project and in every F# project that depends on it, so the action is not offered in a mixed-version solution. The callers are only known after find-references, so the check covers all dependent projects, not only the ones with call sites. Test: Value option is offered when the dependent projects have F# 10.

[xperiandri]

Fixed in eea18fa: the attribute is recognised whatever its target, so [<param: Struct>] ?x is a value option parameter and converts back to ?x. Test: Struct attribute with a target marks a value option parameter.

[xperiandri]

Fixed in eea18fa: each supported module function now carries its argument count, and its qualifier is renamed only when the parameter is the last argument, applied directly or piped. Test: No action (the Option.defaultValue x (Some None) case).

[xperiandri]

Fixed in eea18fa: a call site is now matched with or without its type arguments. The static form C.M<int>(?x = …) was already rewritten; the instance form c.M<int>(?x = …) was not, and now is. (C.M)(?x = …) does not parse (FS0734), so parentheses need no handling. Test: Optional arguments at call sites follow the conversion (both forms).

[xperiandri]

Fixed in eea18fa: only the conversion function and the whitespace after it are removed, so ValueOption.ofOption (* keep *) x becomes (* keep *) x. Test: Optional arguments at call sites follow the conversion.

[abonie]

🤖🕵️ AI review — verify independently.

[abonie]

🤖🕵️ Converting the first ?x creates the second overload’s exact signature, producing FS0438. Check for destination-signature collisions before offering the action; #20547 has the same gap.

type C() =
    static member M(?x: int) = defaultArg x 0
    static member M([<Struct>] ?x: int) = defaultValueArg x 1

[xperiandri]

Fixed in eea18fa: no action when another overload of the member already has the signature the conversion would produce. The overloads are compared parameter by parameter, with their type parameters matched by position. Tests: No action (this repro from both overloads, and a generic pair); Overload that differs in another parameter does not block the conversion covers the opposite case.

[abonie]

🤖🕵️ AI review — verify independently.

[abonie]

🤖🕵️ Named match binder lets the changed representation escape validation: conversion changes x to voption, but leaves Option.defaultValue 0 y untouched and produces FS0001. Follow the bound symbol’s uses or reject this transfer.

type C() =
    static member M(?x: int) =
        match x with
        | y -> Option.defaultValue 0 y

[xperiandri]

Fixed in eea18fa: a match clause that binds the parameter to a name is rejected; only the option cases and _ are accepted as clause heads. Test: No action (this repro).

[abonie]

🤖🕵️ Nested call edits overlap and throw ArgumentException: simplifying the outer ValueOption.toOption replaces a span containing the inner Some edit. Compose nested rewrites before applying SourceText.WithChanges.

type C() =
    static member M(?x: int) = defaultArg x 0

let result =
    C.M(?x = ValueOption.toOption (ValueSome (C.M(?x = Some 1))))

[xperiandri]

Fixed in eea18fa: dropping the outer ValueOption.toOption now removes only the function, not the whole argument, so it no longer overlaps the edit of the nested call. Test: Optional arguments at call sites follow the conversion (this repro).

[T-Gro]

🤖 🕵️ Re-reviewed all recent changes as of fd24fc7; 2 findings

[T-Gro]

🤖 🕵️ [P2] Recreate the computation for each action invocation

Canceling a preview during reference discovery also cancels a later application of the same action, even with an uncanceled application token. The callback restarts the captured changedSolution, but CancellableTaskBuilder.Run retains its mutable state machine on the default scheduler, so the second invocation resumes the first invocation's canceled awaiter.

module M

type C() =
    static member M(?x: int) = defaultArg x 0

let result = C.M(x = 1)

A focused probe loading the unmodified provider and CancellableTasks.fs, with a controlled reference-discovery gate and Roslyn's preview/application APIs, reproduced this under both optimization settings: application was canceled with the preview token and reference discovery started only once. Changing changedSolution to a factory invoked inside this callback made application succeed and discovery start twice. Create a fresh computation per invocation, or make the shared builder safely restartable.

[xperiandri]

Fixed in eea18fa: changedSolution is now a function called inside the callback, so every invocation of the action builds its own computation. Test: Action applies after an invocation that was cancelled; it failed with TaskCanceledException before the change.

[T-Gro]

🤖 🕵️ [P2] Resolve the pipe operator before accepting this use

This checks op_PipeRight only by spelling. A locally defined pipe can require an option even when the continuation resolves to the genuine FSharp.Core Option.defaultValue:

module M

let (|>) (x: int option) f = f x

type C() =
    static member M(?x: int) = x |> Option.defaultValue 0

let result = C.M(x = 1)

The original type-checks, but the current helpers offer the action and produce M([<Struct>] ?x: int) = x |> ValueOption.defaultValue 0, yielding FS0001 for both the operand and continuation. I reproduced the exact edits and errors with the current helper source. Verify that the source pipe resolves to FSharp.Core before allowing this branch; checking only the option function does not establish that the surrounding use preserves its type.

[xperiandri]

Fixed in eea18fa: the piped use is accepted only when |> resolves to the FSharp.Core operator. Test: No action (this repro).

[T-Gro]

The diff is still way too big - apply the NoBloat instructions and CodeCompaction skill.

Especially the massive code comments would benefit not just with drastic reduction, but ideally with well named functions/arguments/bindings/types making the intention clear.

If a well named piece of code just tells what the comment says - delete the comment.

• This diff adds 22 new code comment lines and 2176 new code comment chars.
• Comments bypass the type system and become stale maintenance state. Keep only durable public contracts; express implementation intent through names, functions, active patterns, discriminated unions, and types.

[xperiandri]

Commits d40c554 (source) and c9643f6 (tests) apply the compaction: added comment lines 22 -> 1 and comment characters 2176 -> 123, the one left being the license header, with the explanations now carried by names such as resolvesOnlyToFSharpCore, arityOfOptionKindIndependentFunction, tryEnclosingMember and isUseInMemberBody. ComputeRefactoringsAsync went from eight nested levels of control flow to three (tryCreateAction and changedSolution are their own functions), and the repeated symbol lookup and case check became tryGetSymbolUse and isConvertibleCase. The tests went from 14 methods to 9 and from 568 to 399 lines with the same 36 cases (every input and expected result is kept, the module M header comes from one helper, and each theory row has a name), so the PR now adds 1238 lines instead of 1435. Left as is: tryParameter still folds the whole tree, since ParsedInput.tryPick stops at the caret with different edge rules and would change behaviour.