[Rust] Fixed try finally handler (fable-compiler#3933)

src/Fable.Cli/CHANGELOG.md

@@ -15,6 +15,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * [Rust] Support more System.Array methods and tests (by @ncave)
 * [JS] Add `System.String.Normalize` support (by @DashieTM)
 
+### Fixed
+
+* [Rust] Fixed try finally handler order of execution (by @ncave)
+
 ## 4.22.0 - 2024-10-02
 
 ### Added

src/Fable.Transforms/FableTransforms.fs

@@ -35,7 +35,7 @@ let isTailRecursive identName expr =
             getSubExpressions e |> List.iter (loop false)
         | Sequential exprs ->
             let lastIndex = (List.length exprs) - 1
-            exprs |> List.iteri (fun i e -> loop (i = lastIndex) e)
+            exprs |> List.iteri (fun i e -> loop (inTailPos && i = lastIndex) e)
         | Let(_, value, body) ->
             loop false value
             loop inTailPos body

src/Fable.Transforms/Rust/Fable2Rust.fs

@@ -2829,10 +2829,12 @@ module Util =
             // try...finally
             match finalizer with
             | Some finBody ->
-                let f = makeLocalLambda com ctx [] finBody
-                let finAlloc = makeLibCall com ctx None "Exception" "finally" [ f ]
+                let f = transformLambda com ctx None [] finBody
+                let finCall = makeLibCall com ctx None "Exception" "finally" [ f ]
+                let finPat = makeFullNameIdentPat "__finally__"
+                let letExpr = mkLetExpr finPat finCall
                 let bodyExpr = transformExpr com ctx body
-                [ finAlloc |> mkSemiStmt; bodyExpr |> mkExprStmt ] |> mkStmtBlockExpr
+                [ letExpr |> mkSemiStmt; bodyExpr |> mkExprStmt ] |> mkStmtBlockExpr
             | _ ->
                 // no catch, no finalizer
                 transformExpr com ctx body
@@ -3635,11 +3637,10 @@ module Util =
             TailCallOpportunity = tco
         }
 
-    let isTailRecursive (name: string option) (body: Fable.Expr) =
-        if name.IsNone then
-            false, false
-        else
-            FableTransforms.isTailRecursive name.Value body
+    let isTailRecursive (nameOpt: string option) (body: Fable.Expr) =
+        match nameOpt with
+        | Some name -> FableTransforms.isTailRecursive name body
+        | None -> false, false
 
     let transformFunctionBody com ctx (args: Fable.Ident list) (body: Fable.Expr) =
         match ctx.TailCallOpportunity with

src/fable-library-rust/src/Exception.rs

@@ -1,5 +1,5 @@
 pub mod Exception_ {
-    use crate::Native_::{Any, Box_, LrcPtr};
+    use crate::Native_::{Any, Box_, Func0, LrcPtr};
     use crate::String_::{fromSlice, string};
     use crate::System::Exception;
     use crate::Util_::new_Exception;
@@ -41,14 +41,9 @@ pub mod Exception_ {
         }
     }
 
-    pub struct finally<F, R>(pub F)
-    where
-        F: FnMut() -> R;
+    pub struct finally<R: 'static>(pub Func0<R>);
 
-    impl<F, R> Drop for finally<F, R>
-    where
-        F: FnMut() -> R,
-    {
+    impl<R: 'static> Drop for finally<R> {
         fn drop(&mut self) {
             (self.0)();
         }

tests/Rust/tests/src/TailCallTests.fs

@@ -73,28 +73,28 @@ module Functions =
         | 0 -> x
         | _ -> iterate f (n - 1) (f x)
 
-    // let recWithFinally () =
-    //     let mutable log = ""
-    //     let rec test n =
-    //       try
-    //         log <- log + string "abcde"[n]
-    //         if n < 4 then test (n+1)
-    //       finally
-    //         log <- log + string "ABCDE"[n]
-    //     test 0
-    //     log
-
-    // let recWithUse () =
-    //     let mutable log = ""
-    //     let disp(n) =
-    //       { new System.IDisposable with
-    //           member x.Dispose() = log <- log + string "ABCDE"[n] }
-    //     let rec test n =
-    //       use _disp = disp(n)
-    //       log <- log + string "abcde"[n]
-    //       if n < 4 then test (n+1) else 0
-    //     test 0 |> ignore
-    //     log
+    let recWithFinally () =
+        let mutable log = ""
+        let rec test n =
+            try
+                log <- log + string "abcde".[n]
+                if n < 4 then test (n+1)
+            finally
+                log <- log + string "ABCDE".[n]
+        test 0
+        log
+
+    let recWithUse () =
+        let mutable log = ""
+        let disp(n) =
+            { new System.IDisposable with
+                member x.Dispose() = log <- log + string "ABCDE".[n] }
+        let rec test n =
+            use _disp = disp(n)
+            log <- log + string "abcde".[n]
+            if n < 4 then test (n+1) else 0
+        test 0 |> ignore
+        log
 
 open Functions
 
@@ -133,13 +133,13 @@ and parseTokens tokens = function
     | x::xs -> parseTokens tokens xs
     | [] -> List.rev tokens
 
-// type Element =
-//     | Element of action: (unit->unit) * children: Element list
-//     member this.Activate() =
-//         match this with
-//         | Element(action, children) ->
-//             action()
-//             for child in children do child.Activate()
+type Element =
+    | Element of action: (unit->unit) * children: Element list
+    member this.Activate() =
+        match this with
+        | Element(action, children) ->
+            action()
+            for child in children do child.Activate()
 
 [<Fact>]
 let ``Tailcall works in tail position`` () =
@@ -204,13 +204,13 @@ let ``Tailcall optimization doesn't cause endless loops`` () = // See #675
     |> tryFind "a"
     |> equal None
 
-// [<Fact>]
-// let ``Recursive functions containing finally work`` () =
-//     recWithFinally () |> equal "abcdeEDCBA"
+[<Fact>]
+let ``Recursive functions containing finally work`` () =
+    recWithFinally () |> equal "abcdeEDCBA"
 
-// [<Fact>]
-// let ``Recursive functions containing use work`` () =
-//     recWithUse () |> equal "abcdeEDCBA"
+[<Fact>]
+let ``Recursive functions containing use work`` () =
+    recWithUse () |> equal "abcdeEDCBA"
 
 [<Fact>]
 let ``Function arguments can be optimized`` () = // See #681
@@ -220,22 +220,22 @@ let ``Function arguments can be optimized`` () = // See #681
 let ``Function arguments can be optimized II`` () = // See #681
     iterate ((*) 2) 5 10 |> equal 320
 
-// // See https://github.com/fable-compiler/Fable/issues/1368#issuecomment-434142713
-// [<Fact>]
-// let ``State of internally mutated tail called function parameters is preserved properly`` () =
-//     let rec loop i lst =
-//         if i <= 0
-//         then lst
-//         else loop (i - 1) ((fun () -> i) :: lst)
-//     loop 3 [] |> List.map (fun f -> f()) |> equal [1;2;3]
+// See https://github.com/fable-compiler/Fable/issues/1368#issuecomment-434142713
+[<Fact>]
+let ``State of internally mutated tail called function parameters is preserved properly`` () =
+    let rec loop i lst =
+        if i <= 0
+        then lst
+        else loop (i - 1) ((fun () -> i) :: lst)
+    loop 3 [] |> List.map (fun f -> f()) |> equal [1;2;3]
 
-// [<Fact>]
-// let ``State of internally mutated tail called function parameters is preserved properly II`` () =
-//     let rec loop lst i =
-//         if i <= 0
-//         then lst
-//         else loop ((fun () -> i) :: lst) (i - 1)
-//     loop [] 3 |> List.map (fun f -> f()) |> equal [1;2;3]
+[<Fact>]
+let ``State of internally mutated tail called function parameters is preserved properly II`` () =
+    let rec loop lst i =
+        if i <= 0
+        then lst
+        else loop ((fun () -> i) :: lst) (i - 1)
+    loop [] 3 |> List.map (fun f -> f()) |> equal [1;2;3]
 
 // See https://github.com/fable-compiler/Fable/issues/1368#issuecomment-434142713
 [<Fact>]

tests/Rust/tests/src/TypeTests.fs

@@ -1132,7 +1132,7 @@ let ``copying struct records works`` () = // See #3371
 // let ``reraise works`` () =
 //     try
 //         try
-//             Exception("Will I be reraised?") |> raise
+//             System.Exception("Will I be reraised?") |> raise
 //         with _ ->
 //             try
 //                 reraise()