[TS/Python] Fix invalid this argument type in structs (#4453)

src/Fable.Cli/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* [TS/Python] Fix invalid `this` argument type in structs (#4453) (by @ncave)
 * [JS/TS] Fix `N` format specifier (`ToString("N0")`, `String.Format("{0:N0}", ...)`) producing a trailing dot when precision is 0 (fix #2582) (by @MangelMaxime)
 * [JS/TS] Fix `C0` and `P0` format specifiers producing trailing dot (e.g., `"¤1,000."` → `"¤1,000"`) (by @MangelMaxime)
 * [All] Fix captured side-effect-free values (e.g. empty ResizeArray) being incorrectly inlined into object expression getters in release mode, causing a new instance to be created on each getter call (fixes #3779) (by @MangelMaxime)

src/Fable.Compiler/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* [TS/Python] Fix invalid `this` argument type in structs (#4453) (by @ncave)
 * [JS/TS] Fix `N` format specifier (`ToString("N0")`, `String.Format("{0:N0}", ...)`) producing a trailing dot when precision is 0 (fix #2582) (by @MangelMaxime)
 * [JS/TS] Fix `C0` and `P0` format specifiers producing trailing dot (e.g., `"¤1,000."` → `"¤1,000"`) (by @MangelMaxime)
 * [All] Fix captured side-effect-free values (e.g. empty ResizeArray) being incorrectly inlined into object expression getters in release mode, causing a new instance to be created on each getter call (fixes #3779) (by @MangelMaxime)

src/Fable.Transforms/Fable2Babel.fs

@@ -628,6 +628,14 @@ module Annotation =
         | Replacements.Util.Builtin kind -> makeBuiltinTypeAnnotation com ctx typ kind
         | Fable.DeclaredType(entRef, genArgs) -> com.GetEntity(entRef) |> makeEntityTypeAnnotation com ctx genArgs
 
+    let makeArgTypeAnnotation (com: IBabelCompiler) ctx (id: Fable.Ident) =
+        if com.IsTypeScript then
+            match id.Type, id with
+            | Replacements.Util.IsByRefType com typ, id when id.IsThisArgument -> makeTypeAnnotation com ctx typ |> Some
+            | _ -> makeTypeAnnotation com ctx id.Type |> Some
+        else
+            None
+
     let makeTypeAnnotationIfTypeScript (com: IBabelCompiler) ctx typ expr =
         if com.IsTypeScript then
             match typ, expr with
@@ -3322,7 +3330,7 @@ but thanks to the optimisation done below we get
                 let args' =
                     List.zip args tc.Args
                     |> List.map (fun (id, tcArg) ->
-                        let ta = makeTypeAnnotationIfTypeScript com ctx id.Type None
+                        let ta = makeArgTypeAnnotation com ctx id
 
                         Parameter.parameter (tcArg, ?typeAnnotation = ta)
                     )
@@ -3348,7 +3356,7 @@ but thanks to the optimisation done below we get
             | _ ->
                 args
                 |> List.map (fun a ->
-                    let ta = makeTypeAnnotationIfTypeScript com ctx a.Type None
+                    let ta = makeArgTypeAnnotation com ctx a
                     Parameter.parameter (a.Name, ?typeAnnotation = ta)
                 ),
                 body

src/Fable.Transforms/Python/Fable2Python.Annotation.fs

@@ -754,6 +754,12 @@ let makeBuiltinTypeAnnotation com ctx typ repeatedGenerics kind =
         fableModuleAnnotation com ctx "choice" name resolved, stmts
     | _ -> stdlibModuleTypeHint com ctx "typing" "Any" [] repeatedGenerics
 
+let makeArgTypeAnnotation com ctx repeatedGenerics (id: Fable.Ident) =
+    match id.Type, id with
+    | Replacements.Util.IsByRefType com typ, id when id.IsThisArgument ->
+        typeAnnotation com ctx (Some repeatedGenerics) typ
+    | _ -> typeAnnotation com ctx (Some repeatedGenerics) id.Type
+
 let transformFunctionWithAnnotations
     (com: IPythonCompiler)
     ctx

src/Fable.Transforms/Python/Fable2Python.Transforms.fs

@@ -3083,12 +3083,10 @@ let transformFunction
             // Replace args, see NamedTailCallOpportunity constructor
             let args' =
                 List.zip args tc.Args
-                |> List.map (fun (_id, { Arg = Identifier tcArg }) ->
-                    let id = com.GetIdentifier(ctx, tcArg)
-
-                    let ta, _ = Annotation.typeAnnotation com ctx (Some repeatedGenerics) _id.Type
-
-                    Arg.arg (id, annotation = ta)
+                |> List.map (fun (id, { Arg = Identifier tcArg }) ->
+                    let id2 = com.GetIdentifier(ctx, tcArg)
+                    let ta, _ = Annotation.makeArgTypeAnnotation com ctx repeatedGenerics id
+                    Arg.arg (id2, annotation = ta)
                 )
 
             let varDecls =
@@ -3119,8 +3117,7 @@ let transformFunction
             let args' =
                 args
                 |> List.map (fun id ->
-                    let ta, _ = Annotation.typeAnnotation com ctx (Some repeatedGenerics) id.Type
-
+                    let ta, _ = Annotation.makeArgTypeAnnotation com ctx repeatedGenerics id
                     Arg.arg (ident com ctx id, annotation = ta)
                 )
 

tests/Beam/TypeTests.fs

@@ -43,6 +43,12 @@ type ValueType1<'T>(value: 'T) =
 type ValueType2(i: int, j: int) =
     member x.Value = i + j
 
+[<Struct>]
+type ValueTypeR =
+    val mutable X: float
+    new(x: float) = { X = x }
+    member this.IsEmpty() = this.X < 0.0
+
 [<Struct>]
 type StructUnion = Value of string
 
@@ -645,6 +651,12 @@ let ``test Other Value Types work`` () =
     let p = Point2D(2.)
     p.Y |> equal 2.
 
+[<Fact>]
+let ``test Struct with mutable fields works`` () =
+    let x = ValueTypeR(-10.0)
+    x.X |> equal -10.0
+    x.IsEmpty() |> equal true
+
 [<Fact>]
 let ``test Custom F# exceptions work`` () =
     try
@@ -732,6 +744,7 @@ let ``test Type abbreviation works`` () =
 //     let mutable t2 = ValueType3()
 //     t2.X |> equal 0
 
+
 // Test types for generic parameter static member resolution
 type TestTypeA =
     static member GetValue() = "A"

tests/Dart/src/TypeTests.fs

@@ -264,6 +264,12 @@ open Util
 //     val mutable public X : int
 //   end
 
+// [<Struct>]
+// type ValueTypeR =
+//     val mutable X: float
+//     new(x: float) = { X = x }
+//     member this.IsEmpty() = this.X < 0.0
+
 // [<Struct>]
 // type StructUnion = Value of string
 
@@ -1083,6 +1089,11 @@ let tests() =
 //         t1 |> equal t2
 //         (compare t1 t2) |> equal 0
 
+//     testCase "Struct with mutable fields works" <| fun () ->
+//         let x = ValueTypeR(-10.0)
+//         x.X |> equal -10.0
+//         x.IsEmpty() |> equal true
+
 //     testCase "copying struct records works" <| fun () -> // See #3371
 //         let simple : SimpleRecord = { A = ""; B = "B" }
 //         let simpleRecord = { simple with A = "A" }

tests/Js/Main/TypeTests.fs

@@ -261,13 +261,18 @@ type ValueType2(i: int, j: int) =
     member x.Value = i + j
 
 #if !FABLE_COMPILER_TYPESCRIPT
-[<Struct>]
 type ValueType3 =
   struct
     val mutable public X : int
   end
 #endif
 
+[<Struct>]
+type ValueTypeR =
+    val mutable X: float
+    new(x: float) = { X = x }
+    member this.IsEmpty() = this.X < 0.0
+
 [<Struct>]
 type StructUnion = Value of string
 
@@ -1303,6 +1308,11 @@ let tests =
         (compare t1 t2) |> equal 0
 #endif
 
+    testCase "Struct with mutable fields works" <| fun () ->
+        let x = ValueTypeR(-10.0)
+        x.X |> equal -10.0
+        x.IsEmpty() |> equal true
+
     testCase "copying struct records works" <| fun () -> // See #3371
         let simple : SimpleRecord = { A = ""; B = "B" }
         let simpleRecord = { simple with A = "A" }

tests/Python/TestType.fs

@@ -298,6 +298,12 @@
         val mutable public X: int
     end
 
+[<Struct>]
+type ValueTypeR =
+    val mutable X: float
+    new(x: float) = { X = x }
+    member this.IsEmpty() = this.X < 0.0
+
 [<Struct>]
 type StructUnion = Value of string
 
@@ -586,7 +592,7 @@
 
 type IndexedProps(v: int) =
     let mutable v = v
     member _.Item with get (v2: int) = v + v2 and set v2 (s: string) = v <- v2 + int s
     member _.Item with get (v2: float) = float v + v2 / 2.
 
 [<Interface>]
@@ -1246,6 +1252,12 @@
 
     (compare t1 t2) |> equal 0
 
+[<Fact>]
+let ``test Struct with mutable fields works`` () =
+    let x = ValueTypeR(-10.0)
+    x.X |> equal -10.0
+    x.IsEmpty() |> equal true
+
 [<Fact>]
 let ``test Custom F# exceptions work`` () =
     try

tests/Rust/tests/src/TypeTests.fs

@@ -264,6 +264,12 @@
     val mutable public X : int
   end
 
+[<Struct>]
+type ValueTypeR =
+    val mutable X: float
+    new(x: float) = { X = x }
+    member this.IsEmpty() = this.X < 0.0
+
 [<Struct>]
 type StructUnion = Value of string
 
@@ -507,7 +513,7 @@
 
 type IndexedProps(v: int) =
     let mutable v = v
     member _.Item with get (v2: int) = v + v2 and set v2 (s: string) = v <- v2 + int s
     member _.Item with get (v2: float) = float v + v2 / 2.
 
 [<Interface>]
@@ -1120,6 +1126,12 @@
     t1 |> equal t2
     (compare t1 t2) |> equal 0
 
+[<Fact>]
+let ``Struct with mutable fields works`` () =
+    let x = ValueTypeR(-10.0)
+    x.X |> equal -10.0
+    x.IsEmpty() |> equal true
+
 [<Fact>]
 let ``Unchecked.defaultof works for fields on nested structs`` () =
     let top = TopLevelStruct()