WIP: Add tests for issue #19074 - voption with optional parameter syntax (?x=)

src/Compiler/Checking/Expressions/CheckExpressions.fs

@@ -9934,7 +9934,7 @@ and TcMethodApplication_SplitSynArguments
                 // named optional arguments should always have option type
                 // STRUCT OPTIONS: if we allow struct options as optional arguments then we should relax this and rely
                 // on later inference to work out if this is a struct option or ref option
-                let ty = if isOpt then mkOptionTy denv.g ty else ty
+                let ty = if isOpt && not (denv.g.langVersion.SupportsFeature LanguageFeature.SupportValueOptionsAsOptionalParameters) then mkOptionTy denv.g ty else ty
                 nm, isOpt, x, ty, x.Range)
 
             (Some (unnamedCurriedCallerArgs, namedCurriedCallerArgs), None, exprTy)

src/Compiler/Checking/MethodCalls.fs

@@ -379,7 +379,7 @@ let AdjustCalledArgTypeForOptionals (infoReader: InfoReader) ad enforceNullableO
 
         // FSharpMethod(?x = arg), optional F#-style argument
         | CalleeSide ->
-            // In this case, the called argument will already have option type
+            // In this case, the called argument will already have option/voption type
             calledArgTy, TypeDirectedConversionUsed.No, None
 
         | NotOptional -> 

tests/fsharp/Compiler/Language/OptionalInteropTests.fs

@@ -163,3 +163,86 @@ Test.OverloadedMethodTakingNullableOptionals(x = 6) |> ignore
         let fs = Compilation.Create(fsSrc, CompileOutput.Exe, options = [| $"--langversion:{langVersion}" |], cmplRefs = [cs])
         CompilerAssert.Compile fs
 
+    // Tests for issue #19074: Support voption with optional parameter syntax (?x=)
+    [<Fact>]
+    let ``F# method with voption optional parameter should accept ValueNone with question mark syntax`` () =
+        let fsSrc =
+            """
+open System.Runtime.InteropServices
+
+type MyClass() =
+    member _.Foo([<Optional>] x: int voption) = 
+        match x with
+        | ValueNone -> "none"
+        | ValueSome v -> string v
+
+let c = MyClass()
+let r1 = c.Foo(?x=ValueNone)
+printfn "%s" r1
+            """
+
+        let fs = Compilation.Create(fsSrc, CompileOutput.Exe, options = [| "--langversion:preview" |])
+        CompilerAssert.Compile fs
+
+    [<Fact>]
+    let ``F# method with voption optional parameter should accept ValueSome with question mark syntax`` () =
+        let fsSrc =
+            """
+open System.Runtime.InteropServices
+
+type MyClass() =
+    member _.Foo([<Optional>] x: int voption) = 
+        match x with
+        | ValueNone -> "none"
+        | ValueSome v -> string v
+
+let c = MyClass()
+let r2 = c.Foo(?x=ValueSome 42)
+printfn "%s" r2
+            """
+
+        let fs = Compilation.Create(fsSrc, CompileOutput.Exe, options = [| "--langversion:preview" |])
+        CompilerAssert.Compile fs
+
+    [<Fact>]
+    let ``F# method with voption optional parameter should work without question mark syntax`` () =
+        let fsSrc =
+            """
+open System.Runtime.InteropServices
+
+type MyClass() =
+    member _.Foo([<Optional>] x: int voption) = 
+        match x with
+        | ValueNone -> "none"
+        | ValueSome v -> string v
+
+let c = MyClass()
+let r1 = c.Foo(x=ValueNone)
+let r2 = c.Foo(x=ValueSome 42)
+printfn "%s %s" r1 r2
+            """
+
+        let fs = Compilation.Create(fsSrc, CompileOutput.Exe, options = [| "--langversion:preview" |])
+        CompilerAssert.Compile fs
+
+    [<Fact>]
+    let ``F# method with option optional parameter should still work with question mark syntax`` () =
+        let fsSrc =
+            """
+open System.Runtime.InteropServices
+
+type MyClass() =
+    member _.Foo([<Optional>] x: int option) = 
+        match x with
+        | None -> "none"
+        | Some v -> string v
+
+let c = MyClass()
+let r1 = c.Foo(?x=None)
+let r2 = c.Foo(?x=Some 42)
+printfn "%s %s" r1 r2
+            """
+
+        let fs = Compilation.Create(fsSrc, CompileOutput.Exe, options = [| "--langversion:preview" |])
+        CompilerAssert.Compile fs
+