fix(all): copy mutable struct records by value

src/Fable.Transforms/FSharp2Fable.Util.fs

@@ -850,6 +850,9 @@ module Helpers =
     //      typ.TypeDefinition.DisplayName = "inref" ||
     //      typ.TypeDefinition.DisplayName = "outref")
 
+    let isInRefType (typ: FSharpType) =
+        typ.HasTypeDefinition && typ.TypeDefinition.DisplayName = "inref"
+
     let isByRefValue (value: FSharpMemberOrFunctionOrValue) =
         // Value type "this" is passed as inref, so it has to be excluded
         // (Note: the non-abbreviated type of inref and outref is byref)

src/Fable.Transforms/FSharp2Fable.fs

@@ -770,6 +770,26 @@ let private withDefaultValueFields (com: IFableCompiler) (ctx: Context) (fsType:
     else
         args
 
+let private derefByRefCallee
+    (com: IFableCompiler)
+    (ctx: Context)
+    r
+    (callee: FSharpExpr)
+    (calleeType: FSharpType)
+    (transformedCallee: Fable.Expr)
+    =
+    match callee with
+    | FSharpExprPatterns.Value var when
+        com.Options.Language <> Rust
+        && isByRefType callee.Type
+        && isByRefValue var
+        // An inref argument is passed as the value itself when its source is immutable
+        && not (isInRefType var.FullType)
+        && not (var.IsCompilerGenerated && var.CompiledName = "inputRecord")
+        ->
+        Replacements.Api.getRefCell com r (makeType ctx.GenericArgs calleeType) transformedCallee
+    | _ -> transformedCallee
+
 let rec private transformDecisionTargets
     (com: IFableCompiler)
     (ctx: Context)
@@ -1100,6 +1120,17 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) appliedGenArgs fs
 
                 return (expr, bindings) ||> List.fold (fun e (i, v) -> Fable.Let(i, v, e))
 
+            | FSharpExprPatterns.AddressOf inner when
+                var.IsCompilerGenerated
+                && var.CompiledName = "inputRecord"
+                && com.Options.Language <> Rust
+                ->
+                let! value = transformExpr com ctx [] inner
+                let ctx, ident = putIdentInScope com ctx var (Some value)
+                let ident = { ident with Type = value.Type }
+                let! body = transformExpr com ctx [] body
+                return Fable.Let(ident, value, body)
+
             | _ when isInline var ->
                 let ctx = { ctx with ScopeInlineValues = (var, value) :: ctx.ScopeInlineValues }
 
@@ -1402,7 +1433,14 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) appliedGenArgs fs
         // Getters and Setters
         | FSharpExprPatterns.AnonRecordGet(callee, calleeType, fieldIndex) ->
             let r = makeRangeFrom fsExpr
-            let! callee = transformExpr com ctx [] callee
+
+            let callee =
+                match callee with
+                | IgnoreAddressOf inner when com.Options.Language <> Rust -> inner
+                | _ -> callee
+
+            let! transformedCallee = transformExpr com ctx [] callee
+            let callee = derefByRefCallee com ctx r callee calleeType transformedCallee
 
             let fieldName = calleeType.AnonRecordTypeDetails.SortedFieldNames[fieldIndex]
 
@@ -1414,7 +1452,19 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) appliedGenArgs fs
 
         | FSharpExprPatterns.FSharpFieldGet(callee, calleeType, field) ->
             let r = makeRangeFrom fsExpr
-            let! callee = transformCallee com ctx callee calleeType
+
+            let callee =
+                match callee with
+                | Some(IgnoreAddressOf inner) when com.Options.Language <> Rust -> Some inner
+                | callee -> callee
+
+            let! transformedCallee = transformCallee com ctx callee calleeType
+
+            let callee =
+                match callee with
+                | Some callee -> derefByRefCallee com ctx r callee calleeType transformedCallee
+                | None -> transformedCallee
+
             // let typ = makeType ctx.GenericArgs fsExpr.Type // Doesn't always work
             let typ = resolveFieldType ctx calleeType field.FieldType
 

tests/Beam/RecordTests.fs

@@ -48,6 +48,38 @@ type IntegrityRecord =
 
     override this.ToString() = this.Level
 
+[<Struct>]
+type StructRecordCopied = { T: float; S: string }
+
+[<Struct>]
+type StructRecordWithMutableField = { mutable MutableN: int; FixedN: int }
+
+[<Struct>]
+type StructRecordOrdered = { OrdA: int; OrdB: int; OrdC: int }
+
+type ByRefClassRecord = { BcP: int; BcQ: int }
+
+type ByRefClass =
+    val mutable BkF: int
+    val BkV: int
+    new() = { BkF = 0; BkV = 3 }
+
+let sumStructRecordByRef (r: byref<StructRecordOrdered>) = r.OrdA + r.OrdC
+
+let copyStructRecordByRef (r: byref<StructRecordOrdered>) = { r with OrdB = 99 }
+
+let sumClassRecordByRef (r: byref<ByRefClassRecord>) = r.BcP + r.BcQ
+
+let setClassRecordOutRef (r: outref<ByRefClassRecord>) =
+    r <- { BcP = 4; BcQ = 1 }
+    r.BcP + r.BcQ
+
+let sumClassByRef (r: byref<ByRefClass>) = r.BkF + r.BkV
+
+let sumAnonymousStructRecordByRef (x: byref<struct {| AnX: int; AnY: int |}>) = x.AnX + x.AnY
+
+let mutable moduleStructRecord = { T = 1.0; S = "a" }
+
 [<Fact>]
 let ``test simple record creation works`` () =
     let p = { Name = "Alice"; Age = 30 }
@@ -311,3 +343,58 @@ let ``test Records with ref-type interior mutability`` () =
     x.MutRefValue |> equal "ab"
     x.MutRefValue <- x.MutRefValue + "c"
     x.MutRefValue |> equal "abc"
+
+[<Fact>]
+let ``test copy-and-update of a let mutable struct record keeps the unchanged fields`` () =
+    let mutable mark = { T = 1.0; S = "a" }
+    let copies = ResizeArray()
+    for i in 1..2 do
+        mark <- { T = float i; S = "b" }
+        copies.Add { mark with S = "c" }
+    copies |> Seq.map (fun m -> m.T) |> List.ofSeq |> equal [ 1.0; 2.0 ]
+    copies |> Seq.map (fun m -> m.S) |> List.ofSeq |> equal [ "c"; "c" ]
+
+[<Fact>]
+let ``test copy-and-update of a let mutable struct record with mutable fields keeps the unchanged fields`` () =
+    let mutable p = { MutableN = 1; FixedN = 2 }
+    p.MutableN <- 5
+    let q = { p with FixedN = 9 }
+    q.MutableN |> equal 5
+    q.FixedN |> equal 9
+    p.FixedN |> equal 2
+
+[<Fact>]
+let ``test copy-and-update of a module-level mutable struct record keeps the unchanged fields`` () =
+    moduleStructRecord <- { moduleStructRecord with T = 7.0 }
+    let copy = { moduleStructRecord with S = "b" }
+    copy.T |> equal 7.0
+    copy.S |> equal "b"
+    moduleStructRecord.S |> equal "a"
+
+[<Fact>]
+let ``test field reads and copy-and-update through a byref struct record parameter work`` () =
+    let mutable r = { OrdA = 1; OrdB = 2; OrdC = 3 }
+    sumStructRecordByRef &r |> equal 4
+    let x = copyStructRecordByRef &r
+    (x.OrdA, x.OrdB, x.OrdC) |> equal (1, 99, 3)
+
+[<Fact>]
+let ``test field reads through a byref or outref to a reference type work`` () =
+    let mutable c = { BcP = 1; BcQ = 2 }
+    sumClassRecordByRef &c |> equal 3
+    let mutable o = { BcP = 0; BcQ = 0 }
+    setClassRecordOutRef &o |> equal 5
+    let mutable k = ByRefClass()
+    k.BkF <- 4
+    sumClassByRef &k |> equal 7
+
+[<Fact>]
+let ``test copy-and-update of a let mutable anonymous struct record keeps the unchanged fields`` () =
+    let mutable a = struct {| X = 1; Y = 2 |}
+    let b = {| a with Y = 99 |}
+    (b.X, b.Y) |> equal (1, 99)
+
+[<Fact>]
+let ``test field reads through a byref to an anonymous struct record work`` () =
+    let mutable a = struct {| AnX = 1; AnY = 2 |}
+    sumAnonymousStructRecordByRef &a |> equal 3

tests/Dart/src/RecordTests.fs

@@ -58,6 +58,14 @@ type RecordShadowingFileScope =
         member this.Wrap() = { Value = this.Wrapped }
         member this.Add() = addOne this.addOne
 
+[<Struct>]
+type StructRecordCopied = { T: float; S: string }
+
+[<Struct>]
+type StructRecordWithMutableField = { mutable MutableN: int; FixedN: int }
+
+let mutable moduleStructRecord = { T = 1.0; S = "a" }
+
 let tests() =
     testCase "Anonymous records work" <| fun () ->
         let r = makeAnonRec()
@@ -181,3 +189,32 @@ let tests() =
         let record = { Wrapped = 3; addOne = 7 } :> IWrap
         record.Wrap().Value |> equal 3
         record.Add() |> equal 8
+
+    testCase "Copy-and-update of a let mutable struct record keeps the unchanged fields" <| fun () ->
+        let mutable mark = { T = 1.0; S = "a" }
+        let copies = ResizeArray()
+        for i in 1..2 do
+            mark <- { T = float i; S = "b" }
+            copies.Add { mark with S = "c" }
+        copies |> Seq.map (fun m -> m.T) |> List.ofSeq |> equal [ 1.0; 2.0 ]
+        copies |> Seq.map (fun m -> m.S) |> List.ofSeq |> equal [ "c"; "c" ]
+
+    testCase "Copy-and-update of a let mutable struct record with mutable fields keeps the unchanged fields" <| fun () ->
+        let mutable p = { MutableN = 1; FixedN = 2 }
+        p.MutableN <- 5
+        let q = { p with FixedN = 9 }
+        q.MutableN |> equal 5
+        q.FixedN |> equal 9
+        p.FixedN |> equal 2
+
+    testCase "Copy-and-update of a module-level mutable struct record keeps the unchanged fields" <| fun () ->
+        moduleStructRecord <- { moduleStructRecord with T = 7.0 }
+        let copy = { moduleStructRecord with S = "b" }
+        copy.T |> equal 7.0
+        copy.S |> equal "b"
+        moduleStructRecord.S |> equal "a"
+
+    testCase "Copy-and-update of a let mutable anonymous struct record keeps the unchanged fields" <| fun () ->
+        let mutable a = struct {| X = 1; Y = 2 |}
+        let b = {| a with Y = 99 |}
+        (b.X, b.Y) |> equal (1, 99)

tests/Js/Main/RecordTypeTests.fs

@@ -70,6 +70,38 @@ let holdStructRecord (data: StructRecord) (path: int list) =
             Data = { data with Path = List.rev path }
         }
 
+[<Struct>]
+type StructRecordCopied = { T: float; S: string }
+
+[<Struct>]
+type StructRecordWithMutableField = { mutable MutableN: int; FixedN: int }
+
+[<Struct>]
+type StructRecordOrdered = { OrdA: int; OrdB: int; OrdC: int }
+
+type ByRefClassRecord = { BcP: int; BcQ: int }
+
+type ByRefClass =
+    val mutable BkF: int
+    val BkV: int
+    new() = { BkF = 0; BkV = 3 }
+
+let sumStructRecordByRef (r: byref<StructRecordOrdered>) = r.OrdA + r.OrdC
+
+let copyStructRecordByRef (r: byref<StructRecordOrdered>) = { r with OrdB = 99 }
+
+let sumClassRecordByRef (r: byref<ByRefClassRecord>) = r.BcP + r.BcQ
+
+let setClassRecordOutRef (r: outref<ByRefClassRecord>) =
+    r <- { BcP = 4; BcQ = 1 }
+    r.BcP + r.BcQ
+
+let sumClassByRef (r: byref<ByRefClass>) = r.BkF + r.BkV
+
+let sumAnonymousStructRecordByRef (x: byref<struct {| AnX: int; AnY: int |}>) = x.AnX + x.AnY
+
+let mutable moduleStructRecord = { T = 1.0; S = "a" }
+
 let tests =
   testList "RecordTypes" [
 
@@ -210,4 +242,52 @@ let tests =
         equal 1 a.xs.Count
         equal 1 b.xs.Count
 
+    testCase "Copy-and-update of a let mutable struct record keeps the unchanged fields" <| fun () ->
+        let mutable mark = { T = 1.0; S = "a" }
+        let copies = ResizeArray()
+        for i in 1..2 do
+            mark <- { T = float i; S = "b" }
+            copies.Add { mark with S = "c" }
+        copies |> Seq.map (fun m -> m.T) |> List.ofSeq |> equal [ 1.0; 2.0 ]
+        copies |> Seq.map (fun m -> m.S) |> List.ofSeq |> equal [ "c"; "c" ]
+
+    testCase "Copy-and-update of a let mutable struct record with mutable fields keeps the unchanged fields" <| fun () ->
+        let mutable p = { MutableN = 1; FixedN = 2 }
+        p.MutableN <- 5
+        let q = { p with FixedN = 9 }
+        q.MutableN |> equal 5
+        q.FixedN |> equal 9
+        p.FixedN |> equal 2
+
+    testCase "Copy-and-update of a module-level mutable struct record keeps the unchanged fields" <| fun () ->
+        moduleStructRecord <- { moduleStructRecord with T = 7.0 }
+        let copy = { moduleStructRecord with S = "b" }
+        copy.T |> equal 7.0
+        copy.S |> equal "b"
+        moduleStructRecord.S |> equal "a"
+
+    testCase "Field reads and copy-and-update through a byref struct record parameter work" <| fun () ->
+        let mutable r = { OrdA = 1; OrdB = 2; OrdC = 3 }
+        sumStructRecordByRef &r |> equal 4
+        let x = copyStructRecordByRef &r
+        (x.OrdA, x.OrdB, x.OrdC) |> equal (1, 99, 3)
+
+    testCase "Field reads through a byref or outref to a reference type work" <| fun () ->
+        let mutable c = { BcP = 1; BcQ = 2 }
+        sumClassRecordByRef &c |> equal 3
+        let mutable o = { BcP = 0; BcQ = 0 }
+        setClassRecordOutRef &o |> equal 5
+        let mutable k = ByRefClass()
+        k.BkF <- 4
+        sumClassByRef &k |> equal 7
+
+    testCase "Copy-and-update of a let mutable anonymous struct record keeps the unchanged fields" <| fun () ->
+        let mutable a = struct {| X = 1; Y = 2 |}
+        let b = {| a with Y = 99 |}
+        (b.X, b.Y) |> equal (1, 99)
+
+    testCase "Field reads through a byref to an anonymous struct record work" <| fun () ->
+        let mutable a = struct {| AnX = 1; AnY = 2 |}
+        sumAnonymousStructRecordByRef &a |> equal 3
+
   ]