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T-GroCopilot
T-Gro
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Copilot
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Fix ValueOption optional args via ?param caller syntax (#19711) (#19742)
When the SupportValueOptionsAsOptionalParameters language feature is enabled, do not force option<_> on caller-side ?name = expr arguments during overload inference. Leave the type as a fresh inference variable and let AdjustCalledArgTypeForOptionals (CalleeSide) reconcile against option<_> or voption<_>. Pre-LangVersion-10 behaviour is preserved. Co-authored-by: Copilot <[email protected]>
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‎docs/release-notes/.FSharp.Compiler.Service/11.0.100.md‎

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* Fix parallel compilation of scripts ([PR #19649](https://github.com/dotnet/fsharp/pull/19649))
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* Fix parser recovery, name resolution, and code completion for unfinished enum patterns ([PR #19708](https://github.com/dotnet/fsharp/pull/19708))
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* Parser: fix unexpected diagnostics in debug builds, improve error messages ([PR #19730](https://github.com/dotnet/fsharp/pull/19730))
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* Fix `[<Struct>] ?param` optional parameters could not be passed using the explicit `?param = expr` caller-side syntax with a `ValueOption` value. ([Issue #19711](https://github.com/dotnet/fsharp/issues/19711), [PR #19742](https://github.com/dotnet/fsharp/pull/19742))
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* Fix signature conformance: overloaded member with unit parameter `M(())` now matches sig `member M: unit -> unit`. ([Issue #19596](https://github.com/dotnet/fsharp/issues/19596), [PR #19615](https://github.com/dotnet/fsharp/pull/19615))
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* Parser: recover on unfinished if and binary expressions
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([PR #19724](https://github.com/dotnet/fsharp/pull/19724))

‎src/Compiler/Checking/Expressions/CheckExpressions.fs‎

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@@ -10170,13 +10170,21 @@ and TcMethodApplication_SplitSynArguments
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| _ ->
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let unnamedCurriedCallerArgs = unnamedCurriedCallerArgs |> List.mapSquared MakeUnnamedCallerArgInfo
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let supportsValueOptionalArgs =
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g.langVersion.SupportsFeature LanguageFeature.SupportValueOptionsAsOptionalParameters
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let namedCurriedCallerArgs = namedCurriedCallerArgs |> List.mapSquared (fun (isOpt, nm, x) ->
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let ty = GetNewInferenceTypeForMethodArg cenv x
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// #435263: compiler crash with .net optional parameters and F# optional syntax
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// named optional arguments should always have option type
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// STRUCT OPTIONS: if we allow struct options as optional arguments then we should relax this and rely
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// on later inference to work out if this is a struct option or ref option
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let ty = if isOpt then mkOptionTy denv.g ty else ty
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// For LangVersion < 10 named optional arguments are constrained to option type here
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// so that an early, friendly error is reported. With LangVersion >= 10 the parameter
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// may be a struct-option (voption) — see issue dotnet/fsharp#19711 — so we leave the
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// type as a fresh inference variable and let later unification (CalleeSide branch in
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// AdjustCalledArgTypeForOptionals) pick option<_> or voption<_>.
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let ty =
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if isOpt && not supportsValueOptionalArgs then
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mkOptionTy denv.g ty
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else
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ty
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nm, isOpt, x, ty, x.Range)
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(Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs), None, exprTy)

‎tests/FSharp.Compiler.ComponentTests/Conformance/BasicGrammarElements/MemberDefinitions/OptionalArguments/OptionalArguments.fs‎

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@@ -634,4 +634,81 @@ let main _args =
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|> ILVerifierModule.verifyPEFileWithSystemDlls
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|> run
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|> verifyOutputContains [|"main;18;hello;42;"|]
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// Regression test for https://github.com/dotnet/fsharp/issues/19711
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// `?name = expr` (explicit caller-side question-mark syntax) must accept a
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// ValueOption when the declared parameter is `[<Struct>] ?name`.
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[<Fact>]
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let ``ValueOption optional parameters can be passed using ?param syntax on methods`` () =
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FSharp """
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module Program
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type OptionalArguments() =
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member _.NoProblem (?number : int32) =
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match number with
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| Some v -> printfn "RSome %d" v
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| None -> printfn "RNone"
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member _.Problem ([<Struct>] ?number : int32) =
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match number with
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| ValueSome v -> printfn "VSome %d" v
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| ValueNone -> printfn "VNone"
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[<EntryPoint>]
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let main _ =
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let o = OptionalArguments()
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o.NoProblem 123
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o.NoProblem (number = 123)
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o.NoProblem (?number = None)
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o.NoProblem (?number = Some 123)
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o.NoProblem (?number = Unchecked.defaultof<_>)
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o.Problem 123
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o.Problem (number = 123)
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o.Problem (?number = ValueNone)
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o.Problem (?number = ValueSome 123)
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o.Problem (?number = Unchecked.defaultof<_>)
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0
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"""
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|> asExe
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|> withOptions ["--nowarn:988"]
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|> compileAndRun
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|> shouldSucceed
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|> withOutputContainsAllInOrder [
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"RSome 123"; "RSome 123"; "RNone"; "RSome 123"; "RNone"
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"VSome 123"; "VSome 123"; "VNone"; "VSome 123"; "VNone"
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]
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[<Fact>]
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let ``ValueOption optional parameters can be passed using ?param syntax on constructors`` () =
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FSharp """
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module Program
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type X<'T>([<Struct>] ?x : 'T) =
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member _.M() =
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match x with
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| ValueSome v -> printfn "VSome %A" v
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| ValueNone -> printfn "VNone"
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[<EntryPoint>]
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let main _ =
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X<int>(?x = ValueSome 1).M()
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X<int>(?x = ValueNone).M()
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X<int>(?x = Unchecked.defaultof<_>).M()
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0
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"""
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|> asExe
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|> withOptions ["--nowarn:988"]
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|> compileAndRun
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|> shouldSucceed
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|> withOutputContainsAllInOrder ["VSome 1"; "VNone"; "VNone"]
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[<Fact>]
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let ``ValueOption optional parameters via ?param syntax fail with langversion 9`` () =
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FSharp """
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module Program
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type X() =
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static member M ([<Struct>] ?x : int) = ()
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X.M(?x = ValueSome 1)
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"""
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|> withLangVersion90
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|> typecheck
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|> shouldFail
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|> withDiagnosticMessageMatches "voption"

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