[Python] Fix generic type parameter handling for class methods and ResizeArray Seq compatibility (#4301)

Author: dbrattli

src/Fable.Cli/CHANGELOG.md

@@ -13,7 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-* [Python] Fix `ResizeArray` compatibility with `Seq`/`Array` (by @dbrattli)
+* [Python] Fix `ResizeArray` compatibility with `Seq`/`Array` functions (by @dbrattli)
+* [Python] Fix `FSharpList` generic type parameter handling for `IEnumerable_1` compatibility (by @dbrattli)
 
 ## 5.0.0-alpha.20 - 2025-12-08
 

src/Fable.Compiler/CHANGELOG.md

@@ -13,7 +13,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
-* [Python] Fix `ResizeArray` compatibility with `Seq`/`Array` (by @dbrattli)
+* [Python] Fix `ResizeArray` compatibility with `Seq`/`Array` functions (by @dbrattli)
+* [Python] Fix `FSharpList` generic type parameter handling for `IEnumerable_1` compatibility (by @dbrattli)
 
 ## 5.0.0-alpha.19 - 2025-12-08
 

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

@@ -2775,6 +2775,9 @@ let calculateTypeParams (com: IPythonCompiler) ctx (info: Fable.MemberFunctionOr
         |> Set.union explicitGenerics
         |> Set.union signatureGenerics
         |> Set.union bodyGenerics
+        // Filter out generics that are already defined at class level
+        |> Set.difference
+        <| ctx.ScopedTypeParams
 
     makeFunctionTypeParams com ctx repeatedGenerics
 
@@ -3696,6 +3699,15 @@ let rec transformDeclaration (com: IPythonCompiler) ctx (decl: Fable.Declaration
             if classAttributes.Style = ClassStyle.Properties && not classAttributes.Init then
                 failwithf "ClassAttributes.Init must be true when ClassAttributes.Style is ClassStyle.Properties"
 
+            // Add class generic parameters to scoped type params so methods don't redeclare them
+            let classGenericParams =
+                ent.GenericParameters
+                |> List.map (fun p -> p.Name |> Helpers.clean)
+                |> Set.ofList
+
+            let ctx =
+                { ctx with ScopedTypeParams = Set.union ctx.ScopedTypeParams classGenericParams }
+
             let classMembers =
                 decl.AttachedMembers
                 |> List.collect (fun memb ->

src/Fable.Transforms/Python/Replacements.fs

@@ -47,6 +47,17 @@ let (|TypedArrayCompatible|_|) (com: Compiler) (arrayKind: ArrayKind) t =
 let error com msg =
     Helper.ConstructorCall(makeIdentExpr "Exception", Any, [ msg ])
 
+/// Wraps ResizeArray (Python list) arguments with to_enumerable for Seq module compatibility.
+let wrapResizeArrayToEnumerable com (arg: Expr) =
+    let rec getInnerType expr =
+        match expr with
+        | TypeCast(inner, _) -> getInnerType inner
+        | _ -> expr.Type
+
+    match getInnerType arg with
+    | Array(_, ResizeArray) -> Helper.LibCall(com, "util", "to_enumerable", arg.Type, [ arg ])
+    | _ -> arg
+
 let coreModFor =
     function
     | BclGuid -> "guid"
@@ -1548,6 +1559,9 @@ let formattableString
 let seqModule (com: ICompiler) (ctx: Context) r (t: Type) (i: CallInfo) (thisArg: Expr option) (args: Expr list) =
     // printfn "seqModule: %A" i.CompiledName
 
+    // Wrap ResizeArray arguments with to_enumerable for type compatibility
+    let args = args |> List.map (wrapResizeArrayToEnumerable com)
+
     match i.CompiledName, args with
     | "Cast", [ arg ] -> Some arg // Erase
     | "CreateEvent", [ addHandler; removeHandler; createHandler ] ->