[JS/TS] Fix decimal to char conversion checks (#4054)

* [JS/TS] Fix `decimal` to `char` conversion checks

* simplify the test a little

* add placeholder tests for Python and Rust

src/Fable.Cli/CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * [JS/TS] Fix #4025: No reflection info for pojos (by @alfonsogarciacaro)
 * [JS/TS] Fix #4049: decimal/bigint to integer conversion checks (by @ncave)
+* [JS/TS] Fix `decimal` to `char` conversion checks (by @ManngelMaxime)
 
 ## 5.0.0-alpha.10 - 2025-02-16
 

src/Fable.Compiler/CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * [JS/TS] Fix #4025: No reflection info for pojos (by @alfonsogarciacaro)
 * [JS/TS] Fix #4049: decimal/bigint to integer conversion checks (by @ncave)
+* [JS/TS] Fix `decimal` to `char` conversion checks (by @ManngelMaxime)
 
 ## 5.0.0-alpha.10 - 2025-02-16
 

src/Fable.Transforms/Replacements.fs

@@ -155,10 +155,11 @@ let makeRefFromMutableFunc com ctx r t (value: Expr) =
 
     makeRefCell com r t [ getter; setter ]
 
-let toChar (arg: Expr) =
+let toChar com (ctx: Context) r targetType (arg: Expr) =
     match arg.Type with
     | Char -> arg
     | String -> TypeCast(arg, Char)
+    | Number(Decimal, _) -> Helper.LibCall(com, "Decimal", "toChar", Char, [ arg ], ?loc = r)
     | _ -> Helper.GlobalCall("String", Char, [ arg ], memb = "fromCharCode")
 
 let toString com (ctx: Context) r (args: Expr list) =
@@ -380,7 +381,7 @@ let applyOp (com: ICompiler) (ctx: Context) r t opName (args: Expr list) =
         let toUInt16 e = toInt com ctx None UInt16.Number [ e ]
 
         Operation(Binary(op, toUInt16 left, toUInt16 right), Tags.empty, UInt16.Number, r)
-        |> toChar
+        |> toChar com ctx r t
 
     let truncateUnsigned operation = // see #1550
         match t with
@@ -1216,7 +1217,7 @@ let operators (com: ICompiler) (ctx: Context) r t (i: CallInfo) (thisArg: Expr o
     | ("ToInt64" | "ToUInt64" | "ToIntPtr" | "ToUIntPtr"), _ -> toLong com ctx r t args |> Some
     | ("ToSingle" | "ToDouble"), _ -> toFloat com ctx r t args |> Some
     | "ToDecimal", _ -> toDecimal com ctx r t args |> Some
-    | "ToChar", _ -> toChar args.Head |> Some
+    | "ToChar", _ -> toChar com ctx r t args.Head |> Some
     | "ToString", _ -> toString com ctx r args |> Some
     | "CreateSequence", [ xs ] -> TypeCast(xs, t) |> Some
     | ("CreateDictionary" | "CreateReadOnlyDictionary"), [ arg ] -> makeDictionary com ctx r t arg |> Some
@@ -2461,6 +2462,7 @@ let decimals (com: ICompiler) (ctx: Context) r (t: Type) (i: CallInfo) (thisArg:
             | Floats _ -> toFloat com ctx r t args |> Some
             | Decimal -> toDecimal com ctx r t args |> Some
             | _ -> None
+        | Char -> toChar com ctx r t args.Head |> Some
         | _ -> None
     | ("Ceiling" | "Floor" | "Round" | "Truncate" | "Min" | "Max" | "MinMagnitude" | "MaxMagnitude" | "Clamp" | "Add" | "Subtract" | "Multiply" | "Divide" | "Remainder" | "Negate" as meth),
       _ ->
@@ -2925,7 +2927,7 @@ let convert (com: ICompiler) (ctx: Context) r t (i: CallInfo) (_: Expr option) (
     | "ToSingle"
     | "ToDouble" -> toFloat com ctx r t args |> Some
     | "ToDecimal" -> toDecimal com ctx r t args |> Some
-    | "ToChar" -> toChar args.Head |> Some
+    | "ToChar" -> toChar com ctx r t args.Head |> Some
     | "ToString" -> toString com ctx r args |> Some
     | "ToBase64String"
     | "FromBase64String" ->

src/fable-library-ts/CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+* [JS/TS] Fix #4049: decimal/bigint to integer conversion checks (by @ncave)
+* [JS/TS] Fix `decimal` to `char` conversion checks (by @ManngelMaxime)
+
 ## 2.0.0-beta.1 - 2025-02-16
 
 * Compiled with Fable 5.0.0-alpha.10

src/fable-library-ts/Decimal.ts

@@ -146,6 +146,14 @@ export function toNumber(x: Decimal): number {
   return +x;
 }
 
+export function toChar(x: Decimal): string {
+  const n = toNumber(x);
+  if (n < 0 || n > 65535 || isNaN(n)) {
+    throw new Error("Value was either too large or too small for a character.");
+  }
+  return String.fromCharCode(n);
+}
+
 export function toInt8(x: Decimal): int8 { return bigInt.toInt8(fromDecimal(x)); }
 export function toUInt8(x: Decimal): uint8 { return bigInt.toUInt8(fromDecimal(x)); }
 export function toInt16(x: Decimal): int16 { return bigInt.toInt16(fromDecimal(x)); }

tests/Js/Main/ConvertTests.fs

@@ -1065,6 +1065,10 @@ let tests =
     // System.Decimal
     //-------------------------------------
 
+    testCase "Decimal.ToChar works" <| fun () ->
+        let value = 'A'
+        char (decimal (int value)) |> equal value
+
     testCase "Decimal.ToSByte works" <| fun () ->
         let value = 0x02y
         sbyte (decimal (int32 value)) |> equal value
@@ -1107,6 +1111,7 @@ let tests =
 
     testCase "Decimal to integer conversions are min-checked" <| fun () ->
         let x = Decimal.MinValue
+        throwsAnyError (fun () -> char x)
         throwsAnyError (fun () -> int8 x)
         throwsAnyError (fun () -> uint8 x)
         throwsAnyError (fun () -> int16 x)
@@ -1120,6 +1125,7 @@ let tests =
 
     testCase "Decimal to integer conversions are max-checked" <| fun () ->
         let x = Decimal.MaxValue
+        throwsAnyError (fun () -> char x)
         throwsAnyError (fun () -> int8 x)
         throwsAnyError (fun () -> uint8 x)
         throwsAnyError (fun () -> int16 x)

tests/Python/TestConvert.fs

@@ -1156,6 +1156,11 @@ let ``test BitConverter.ToString 3 works`` () =
 // System.Decimal
 //-------------------------------------
 
+// [<Fact>]
+// let ``Decimal.ToChar works`` () =
+//     let value = 'A'
+//     char (decimal (int value)) |> equal value
+
 [<Fact>]
 let ``test Decimal.ToSByte works`` () =
     let value = 0x02y
@@ -1209,6 +1214,7 @@ let ``test Decimal.ToDouble works`` () =
 // [<Fact>]
 // let ``test Decimal to integer conversions are min-checked`` () =
 //     let x = Decimal.MinValue
+//     throwsAnyError (fun () -> char x)
 //     throwsAnyError (fun () -> int8 x)
 //     throwsAnyError (fun () -> uint8 x)
 //     throwsAnyError (fun () -> int16 x)
@@ -1223,6 +1229,7 @@ let ``test Decimal.ToDouble works`` () =
 // [<Fact>]
 // let ``test Decimal to integer conversions are max-checked`` () =
 //     let x = Decimal.MaxValue
+//     throwsAnyError (fun () -> char x)
 //     throwsAnyError (fun () -> int8 x)
 //     throwsAnyError (fun () -> uint8 x)
 //     throwsAnyError (fun () -> int16 x)

tests/Rust/tests/src/ConvertTests.fs

@@ -1204,6 +1204,11 @@ let ``BitConverter.ToString 3 works`` () =
 // System.Decimal
 //-------------------------------------
 
+// [<Fact>]
+// let ``Decimal.ToChar works`` () =
+//     let value = 'A'
+//     char (decimal (int value)) |> equal value
+
 [<Fact>]
 let ``Decimal.ToSByte works`` () =
     let value = 0x02y
@@ -1257,6 +1262,7 @@ let ``Decimal.ToDouble works`` () =
 [<Fact>]
 let ``Decimal to integer conversions are min-checked`` () =
     let x = Decimal.MinValue
+    // throwsAnyError (fun () -> char x)
     throwsAnyError (fun () -> int8 x)
     throwsAnyError (fun () -> uint8 x)
     throwsAnyError (fun () -> int16 x)
@@ -1271,6 +1277,7 @@ let ``Decimal to integer conversions are min-checked`` () =
 [<Fact>]
 let ``Decimal to integer conversions are max-checked`` () =
     let x = Decimal.MaxValue
+    // throwsAnyError (fun () -> char x)
     throwsAnyError (fun () -> int8 x)
     throwsAnyError (fun () -> uint8 x)
     throwsAnyError (fun () -> int16 x)