Fable2Python.fs

module rec Fable.Transforms.Fable2Python

open System
open System.Collections.Generic
open System.Text.RegularExpressions

open Fable
open Fable.AST
open Fable.AST.Python
open Fable.Py

type ReturnStrategy =
    /// Return last expression
    | Return
    | ReturnUnit
    /// Return within a with-statement (to make sure we don't TC with statements)
    | ResourceManager
    | Assign of Expression
    | Target of Identifier

type Import =
    {
        Module: string
        LocalIdent: Identifier
        Name: string option
    }

type ITailCallOpportunity =
    abstract Label: string
    abstract Args: Arg list
    abstract IsRecursiveRef: Fable.Expr -> bool

type UsedNames =
    {
        RootScope: HashSet<string>
        DeclarationScopes: HashSet<string>
        CurrentDeclarationScope: HashSet<string>
    }

/// Python specific, used for keeping track of existing variable bindings to
/// know if we need to declare an identifier as nonlocal or global.
type BoundVars =
    {
        EnclosingScope: HashSet<string>
        LocalScope: HashSet<string>
        Inceptions: int
    }

    member this.EnterScope() =
        // printfn "Entering scope"
        let enclosingScope = HashSet<string>()
        enclosingScope.UnionWith(this.EnclosingScope)
        enclosingScope.UnionWith(this.LocalScope)

        {
            LocalScope = HashSet()
            EnclosingScope = enclosingScope
            Inceptions = this.Inceptions + 1
        }

    member this.Bind(name: string) = this.LocalScope.Add name |> ignore

    member this.Bind(ids: Identifier list) =
        for Identifier name in ids do
            this.LocalScope.Add name |> ignore

    member this.NonLocals(idents: Identifier list) =
        [
            for ident in idents do
                let (Identifier name) = ident

                if not (this.LocalScope.Contains name) && this.EnclosingScope.Contains name then
                    ident
                else
                    this.Bind(name)
        ]

type Context =
    {
        File: Fable.File
        UsedNames: UsedNames
        BoundVars: BoundVars
        DecisionTargets: (Fable.Ident list * Fable.Expr) list
        HoistVars: Fable.Ident list -> bool
        TailCallOpportunity: ITailCallOpportunity option
        OptimizeTailCall: unit -> unit
        ScopedTypeParams: Set<string>
        TypeParamsScope: int
    }

type IPythonCompiler =
    inherit Compiler
    abstract AddTypeVar: ctx: Context * name: string -> Expression
    abstract AddExport: name: string -> Expression
    abstract GetIdentifier: ctx: Context * name: string -> Identifier
    abstract GetIdentifierAsExpr: ctx: Context * name: string -> Expression
    abstract GetAllImports: unit -> Import list
    abstract GetAllExports: unit -> HashSet<string>
    abstract GetAllTypeVars: unit -> HashSet<string>

    abstract GetImportExpr: Context * moduleName: string * ?name: string * ?loc: SourceLocation -> Expression

    abstract TransformAsExpr: Context * Fable.Expr -> Expression * Statement list

    abstract TransformAsStatements: Context * ReturnStrategy option * Fable.Expr -> Statement list

    abstract TransformImport: Context * selector: string * path: string -> Expression

    abstract TransformFunction:
        Context * string option * Fable.Ident list * Fable.Expr * Set<string> -> Arguments * Statement list

    abstract WarnOnlyOnce: string * ?range: SourceLocation -> unit

// TODO: All things that depend on the library should be moved to Replacements
// to become independent of the specific implementation
module Lib =
    let libCall (com: IPythonCompiler) ctx r moduleName memberName args =
        Expression.call (com.TransformImport(ctx, memberName, getLibPath com moduleName), args, ?loc = r)

    let libConsCall (com: IPythonCompiler) ctx r moduleName memberName args =
        Expression.call (com.TransformImport(ctx, memberName, getLibPath com moduleName), args, ?loc = r)

    let libValue (com: IPythonCompiler) ctx moduleName memberName =
        com.TransformImport(ctx, memberName, getLibPath com moduleName)

    let tryPyConstructor (com: IPythonCompiler) ctx ent =
        match Py.Replacements.tryConstructor com ent with
        | Some e -> com.TransformAsExpr(ctx, e) |> Some
        | None -> None

    let pyConstructor (com: IPythonCompiler) ctx ent =
        let entRef = Py.Replacements.constructor com ent
        com.TransformAsExpr(ctx, entRef)

module Reflection =
    open Lib

    let private libReflectionCall (com: IPythonCompiler) ctx r memberName args =
        libCall com ctx r "reflection" (memberName + "_type") args

    let private transformRecordReflectionInfo com ctx r (ent: Fable.Entity) generics =
        // TODO: Refactor these three bindings to reuse in transformUnionReflectionInfo
        let fullname = ent.FullName
        let fullnameExpr = Expression.stringConstant fullname

        let genMap =
            let genParamNames =
                ent.GenericParameters |> List.mapToArray (fun x -> x.Name) |> Seq.toList

            List.zip genParamNames generics |> Map

        let fields, stmts =
            ent.FSharpFields
            |> Seq.map (fun fi ->
                let typeInfo, stmts = transformTypeInfo com ctx r genMap fi.FieldType

                let name = fi.Name |> Naming.toSnakeCase |> Helpers.clean

                (Expression.tuple [ Expression.stringConstant name; typeInfo ]), stmts
            )
            |> Seq.toList
            |> Helpers.unzipArgs

        let fields = Expression.lambda (Arguments.arguments [], Expression.list fields)

        let py, stmts' = pyConstructor com ctx ent

        [ fullnameExpr; Expression.list generics; py; fields ]
        |> libReflectionCall com ctx None "record",
        stmts @ stmts'

    let private transformUnionReflectionInfo com ctx r (ent: Fable.Entity) generics =
        let fullname = ent.FullName
        let fullnameExpr = Expression.stringConstant fullname

        let genMap =
            let genParamNames =
                ent.GenericParameters |> List.map (fun x -> x.Name) |> Seq.toList

            List.zip genParamNames generics |> Map

        let cases =
            ent.UnionCases
            |> Seq.map (fun uci ->
                uci.UnionCaseFields
                |> List.map (fun fi ->
                    Expression.tuple
                        [
                            fi.Name |> Expression.stringConstant
                            let expr, _stmts = transformTypeInfo com ctx r genMap fi.FieldType

                            expr
                        ]
                )
                |> Expression.list
            )
            |> Seq.toList

        let cases = Expression.lambda (Arguments.arguments [], Expression.list cases)

        let py, stmts = pyConstructor com ctx ent

        [ fullnameExpr; Expression.list generics; py; cases ]
        |> libReflectionCall com ctx None "union",
        stmts

    let transformTypeInfo
        (com: IPythonCompiler)
        ctx
        r
        (genMap: Map<string, Expression>)
        t
        : Expression * Statement list
        =
        let primitiveTypeInfo name =
            libValue com ctx "Reflection" (name + "_type")

        let numberInfo kind =
            getNumberKindName kind |> primitiveTypeInfo

        let nonGenericTypeInfo fullname =
            [ Expression.stringConstant fullname ] |> libReflectionCall com ctx None "class"

        let resolveGenerics generics : Expression list * Statement list =
            generics
            |> Array.map (transformTypeInfo com ctx r genMap)
            |> List.ofArray
            |> Helpers.unzipArgs

        let genericTypeInfo name genArgs =
            let resolved, stmts = resolveGenerics genArgs
            libReflectionCall com ctx None name resolved, stmts

        let genericEntity (fullname: string) (generics: Expression list) =
            libReflectionCall
                com
                ctx
                None
                "class"
                [
                    Expression.stringConstant fullname
                    if not (List.isEmpty generics) then
                        Expression.list generics
                ]

        match t with
        | Fable.Measure _
        | Fable.Any -> primitiveTypeInfo "obj", []
        | Fable.GenericParam(name = name) ->
            match Map.tryFind name genMap with
            | Some t -> t, []
            | None ->
                Replacements.Util.genericTypeInfoError name |> addError com [] r

                Expression.none, []
        | Fable.Unit -> primitiveTypeInfo "unit", []
        | Fable.Boolean -> primitiveTypeInfo "bool", []
        | Fable.Char -> primitiveTypeInfo "char", []
        | Fable.String -> primitiveTypeInfo "string", []
        | Fable.Number(kind, info) ->
            match info with
            | Fable.NumberInfo.IsEnum entRef ->
                let ent = com.GetEntity(entRef)

                let cases =
                    ent.FSharpFields
                    |> Seq.choose (fun fi ->
                        match fi.Name with
                        | "value__" -> None
                        | name ->
                            let value =
                                match fi.LiteralValue with
                                | Some v -> Convert.ToDouble v
                                | None -> 0.

                            Expression.tuple [ Expression.stringConstant name; Expression.floatConstant value ]
                            |> Some
                    )
                    |> Seq.toList
                    |> Expression.list

                [ Expression.stringConstant entRef.FullName; numberInfo kind; cases ]
                |> libReflectionCall com ctx None "enum",
                []
            | _ -> numberInfo kind, []
        | Fable.LambdaType(argType, returnType) -> genericTypeInfo "lambda" [| argType; returnType |]
        | Fable.DelegateType(argTypes, returnType) -> genericTypeInfo "delegate" [| yield! argTypes; yield returnType |]
        | Fable.Tuple(genArgs, _) -> genericTypeInfo "tuple" (List.toArray genArgs)
        | Fable.Option(genArg, _) -> genericTypeInfo "option" [| genArg |]
        | Fable.Array(genArg, _) -> genericTypeInfo "array" [| genArg |]
        | Fable.List genArg -> genericTypeInfo "list" [| genArg |]
        | Fable.Regex -> nonGenericTypeInfo Types.regex, []
        | Fable.MetaType -> nonGenericTypeInfo Types.type_, []
        | Fable.AnonymousRecordType(fieldNames, genArgs, _isStruct) ->
            let genArgs, stmts = resolveGenerics (List.toArray genArgs)

            List.zip (List.ofArray fieldNames) genArgs
            |> List.map (fun (k, t) -> Expression.tuple [ Expression.stringConstant k; t ])
            |> libReflectionCall com ctx None "anonRecord",
            stmts
        | Fable.DeclaredType(entRef, generics) ->
            let fullName = entRef.FullName

            match fullName, generics with
            | Replacements.Util.BuiltinEntity kind ->
                match kind with
                | Replacements.Util.BclGuid
                | Replacements.Util.BclTimeSpan
                | Replacements.Util.BclDateTime
                | Replacements.Util.BclDateTimeOffset
                | Replacements.Util.BclDateOnly
                | Replacements.Util.BclTimeOnly
                | Replacements.Util.BclTimer -> genericEntity fullName [], []
                | Replacements.Util.BclHashSet gen
                | Replacements.Util.FSharpSet gen ->
                    let gens, stmts = transformTypeInfo com ctx r genMap gen
                    genericEntity fullName [ gens ], stmts
                | Replacements.Util.BclDictionary(key, value)
                | Replacements.Util.BclKeyValuePair(key, value)
                | Replacements.Util.FSharpMap(key, value) ->
                    let keys, stmts = transformTypeInfo com ctx r genMap key

                    let values, stmts' = transformTypeInfo com ctx r genMap value

                    genericEntity fullName [ keys; values ], stmts @ stmts'
                | Replacements.Util.FSharpResult(ok, err) ->
                    let ent = com.GetEntity(entRef)
                    let ok', stmts = transformTypeInfo com ctx r genMap ok
                    let err', stmts' = transformTypeInfo com ctx r genMap err

                    let expr, stmts'' = transformUnionReflectionInfo com ctx r ent [ ok'; err' ]

                    expr, stmts @ stmts' @ stmts''
                | Replacements.Util.FSharpChoice gen ->
                    let ent = com.GetEntity(entRef)

                    let gen, stmts =
                        List.map (transformTypeInfo com ctx r genMap) gen |> Helpers.unzipArgs

                    let expr, stmts' = gen |> transformUnionReflectionInfo com ctx r ent

                    expr, stmts @ stmts'
                | Replacements.Util.FSharpReference gen ->
                    let ent = com.GetEntity(entRef)
                    let gen, stmts = transformTypeInfo com ctx r genMap gen

                    let expr, stmts' = [ gen ] |> transformRecordReflectionInfo com ctx r ent

                    expr, stmts @ stmts'
            | _ ->
                let ent = com.GetEntity(entRef)

                let generics, stmts =
                    generics |> List.map (transformTypeInfo com ctx r genMap) |> Helpers.unzipArgs
                // Check if the entity is actually declared in Python code
                if
                    ent.IsInterface
                    || FSharp2Fable.Util.isErasedOrStringEnumEntity ent
                    || FSharp2Fable.Util.isGlobalOrImportedEntity ent
                    || FSharp2Fable.Util.isReplacementCandidate entRef
                then
                    genericEntity ent.FullName generics, stmts
                else
                    let reflectionMethodExpr =
                        FSharp2Fable.Util.entityIdentWithSuffix com entRef Naming.reflectionSuffix

                    let callee, stmts' = com.TransformAsExpr(ctx, reflectionMethodExpr)

                    Expression.call (callee, generics), stmts @ stmts'

    let transformReflectionInfo com ctx r (ent: Fable.Entity) generics =
        if ent.IsFSharpRecord then
            transformRecordReflectionInfo com ctx r ent generics
        elif ent.IsFSharpUnion then
            transformUnionReflectionInfo com ctx r ent generics
        else
            let fullname = ent.FullName

            let exprs, stmts =
                [
                    yield Expression.stringConstant fullname, []
                    match generics with
                    | [] -> yield Util.undefined None, []
                    | generics -> yield Expression.list generics, []
                    match tryPyConstructor com ctx ent with
                    | Some(Expression.Name { Id = name }, stmts) ->
                        yield Expression.name (name.Name |> Naming.toSnakeCase), stmts
                    | Some(cons, stmts) -> yield cons, stmts
                    | None -> ()
                    match ent.BaseType with
                    | Some d ->
                        let genMap =
                            Seq.zip ent.GenericParameters generics
                            |> Seq.map (fun (p, e) -> p.Name, e)
                            |> Map

                        yield
                            Fable.DeclaredType(d.Entity, d.GenericArgs)
                            |> transformTypeInfo com ctx r genMap
                    | None -> ()
                ]
                |> Helpers.unzipArgs

            exprs |> libReflectionCall com ctx r "class", stmts

    let private ofString s = Expression.stringConstant s
    let private ofArray exprs = Expression.list exprs

    let transformTypeTest (com: IPythonCompiler) ctx range expr (typ: Fable.Type) : Expression * Statement list =
        let warnAndEvalToFalse msg =
            "Cannot type test (evals to false): " + msg |> addWarning com [] range

            Expression.boolConstant false

        let pyTypeof (primitiveType: string) (Util.TransformExpr com ctx (expr, stmts)) : Expression * Statement list =
            let typeof =
                let func = Expression.name (Identifier("type"))
                let str = Expression.name (Identifier("str"))
                let typ = Expression.call (func, [ expr ])
                Expression.call (str, [ typ ])

            Expression.compare (typeof, [ Eq ], [ Expression.stringConstant primitiveType ], ?loc = range), stmts

        let pyInstanceof consExpr (Util.TransformExpr com ctx (expr, stmts)) : Expression * Statement list =
            let func = Expression.name (Identifier("isinstance"))

            let args = [ expr; consExpr ]

            Expression.call (func, args), stmts

        match typ with
        | Fable.Measure _ // Dummy, shouldn't be possible to test against a measure type
        | Fable.Any -> Expression.boolConstant true, []
        | Fable.Unit ->
            let expr, stmts = com.TransformAsExpr(ctx, expr)

            Expression.compare (expr, [ Is ], [ Util.undefined None ], ?loc = range), stmts
        | Fable.Boolean -> pyTypeof "<class 'bool'>" expr
        | Fable.Char
        | Fable.String -> pyTypeof "<class 'str'>" expr
        | Fable.Number(kind, _b) ->
            match kind, typ with
            | _, Fable.Type.Number(Int8, _) -> pyTypeof "<class 'fable_modules.fable_library.types.int8'>" expr
            | _, Fable.Type.Number(UInt8, _) -> pyTypeof "<class 'fable_modules.fable_library.types.uint8'>" expr
            | _, Fable.Type.Number(Int16, _) -> pyTypeof "<class 'fable_modules.fable_library.types.int16'>" expr
            | _, Fable.Type.Number(UInt16, _) -> pyTypeof "<class 'fable_modules.fable_library.types.uint16'>" expr
            | _, Fable.Type.Number(Int32, _) -> pyTypeof "<class 'int'>" expr
            | _, Fable.Type.Number(UInt32, _) -> pyTypeof "<class 'fable_modules.fable_library.types.uint32'>" expr
            | _, Fable.Type.Number(Int64, _) -> pyTypeof "<class 'fable_modules.fable_library.types.int64'>" expr
            | _, Fable.Type.Number(UInt64, _) -> pyTypeof "<class 'fable_modules.fable_library.types.uint64'>" expr
            | _, Fable.Type.Number(Float32, _) -> pyTypeof "<class 'fable_modules.fable_library.types.float32'>" expr
            | _, Fable.Type.Number(Float64, _) -> pyTypeof "<class 'float'>" expr
            | _, Fable.Type.Number(Decimal, _) -> pyTypeof "<class 'decimal.Decimal'>" expr
            | _ -> pyTypeof "<class 'int'>" expr

        | Fable.Regex -> pyInstanceof (com.GetImportExpr(ctx, "typing", "Pattern")) expr
        | Fable.LambdaType _
        | Fable.DelegateType _ -> pyTypeof "<class 'function'>" expr
        | Fable.Array _
        | Fable.Tuple _ ->
            let expr, stmts = com.TransformAsExpr(ctx, expr)
            libCall com ctx None "util" "isArrayLike" [ expr ], stmts
        | Fable.List _ -> pyInstanceof (libValue com ctx "List" "FSharpList") expr
        | Fable.AnonymousRecordType _ -> warnAndEvalToFalse "anonymous records", []
        | Fable.MetaType -> pyInstanceof (libValue com ctx "Reflection" "TypeInfo") expr
        | Fable.Option _ -> warnAndEvalToFalse "options", [] // TODO
        | Fable.GenericParam _ -> warnAndEvalToFalse "generic parameters", []
        | Fable.DeclaredType(ent, genArgs) ->
            match ent.FullName with
            | Types.idisposable ->
                match expr with
                | MaybeCasted(ExprType(Fable.DeclaredType(ent2, _))) when
                    com.GetEntity(ent2) |> FSharp2Fable.Util.hasInterface Types.idisposable
                    ->
                    Expression.boolConstant true, []
                | _ ->
                    let expr, stmts = com.TransformAsExpr(ctx, expr)
                    libCall com ctx None "util" "isDisposable" [ expr ], stmts
            | Types.ienumerable ->
                let expr, stmts = com.TransformAsExpr(ctx, expr)

                [ expr ] |> libCall com ctx None "util" "isIterable", stmts
            | Types.array ->
                let expr, stmts = com.TransformAsExpr(ctx, expr)

                [ expr ] |> libCall com ctx None "util" "isArrayLike", stmts
            | Types.exception_ ->
                let expr, stmts = com.TransformAsExpr(ctx, expr)

                [ expr ] |> libCall com ctx None "types" "isException", stmts
            | Types.datetime -> pyInstanceof (com.GetImportExpr(ctx, "datetime", "datetime")) expr
            | _ ->
                let ent = com.GetEntity(ent)

                if ent.IsInterface then
                    match FSharp2Fable.Util.tryGlobalOrImportedEntity com ent with
                    | Some typeExpr ->
                        let typeExpr, stmts = com.TransformAsExpr(ctx, typeExpr)
                        let expr, stmts' = pyInstanceof typeExpr expr
                        expr, stmts @ stmts'
                    | None -> warnAndEvalToFalse "interfaces", []
                else
                    match tryPyConstructor com ctx ent with
                    | Some(cons, stmts) ->
                        if not (List.isEmpty genArgs) then
                            com.WarnOnlyOnce("Generic args are ignored in type testing", ?range = range)

                        let expr, stmts' = pyInstanceof cons expr
                        expr, stmts @ stmts'
                    | None -> warnAndEvalToFalse ent.FullName, []

module Helpers =
    /// Returns true if the first field type can be None in Python
    let isOptional (fields: Fable.Ident[]) =
        if fields.Length < 1 then
            false
        else
            match fields[0].Type with
            | Fable.GenericParam _ -> true
            | Fable.Option _ -> true
            | Fable.Unit -> true
            | Fable.Any -> true
            | _ -> false

    let removeNamespace (fullName: string) =
        fullName.Split('.')
        |> Array.last
        |> (fun name -> name.Replace("`", "_"))
        |> Helpers.clean

    let getUniqueIdentifier (name: string) : Identifier =
        let idx = Naming.getUniqueIndex ()

        let deliminator =
            if Char.IsLower name[0] then
                "_"
            else
                ""

        Identifier($"{name}{deliminator}{idx}")

    /// Replaces all '$' and `.`with '_'
    let clean (name: string) =
        (name, Naming.NoMemberPart) ||> Naming.sanitizeIdent (fun _ -> false)

    let unzipArgs (args: (Expression * Statement list) list) : Expression list * Statement list =
        let stmts = args |> List.map snd |> List.collect id
        let args = args |> List.map fst
        args, stmts

    /// A few statements in the generated Python AST do not produce any effect,
    /// and should not be printed.
    let isProductiveStatement (stmt: Statement) =
        let rec hasNoSideEffects (e: Expression) =
            match e with
            | Constant _ -> true
            | Dict { Keys = keys } -> keys.IsEmpty // Empty object
            | Name _ -> true // E.g `void 0` is translated to Name(None)
            | _ -> false

        match stmt with
        // Remove `self = self`
        | Statement.Assign {
                               Targets = [ Name { Id = Identifier x } ]
                               Value = Name { Id = Identifier y }
                           } when x = y -> None
        | Statement.AnnAssign {
                                  Target = Name { Id = Identifier x }
                                  Value = Some(Name { Id = Identifier y })
                              } when x = y -> None
        | Expr expr ->
            if hasNoSideEffects expr.Value then
                None
            else
                Some stmt
        | _ -> Some stmt

    let toString (e: Fable.Expr) =
        let callInfo = Fable.CallInfo.Create(args = [ e ])
        makeIdentExpr "str" |> makeCall None Fable.String callInfo

// https://www.python.org/dev/peps/pep-0484/
module Annotation =
    open Lib

    let getEntityGenParams (ent: Fable.Entity) =
        ent.GenericParameters |> Seq.map (fun x -> x.Name) |> Set.ofSeq

    let makeTypeParamDecl (com: IPythonCompiler) ctx (genParams: Set<string>) =
        if (Set.isEmpty genParams) then
            []
        else
            com.GetImportExpr(ctx, "typing", "Generic") |> ignore

            let genParams =
                genParams
                |> Set.toList
                |> List.map (fun genParam -> com.AddTypeVar(ctx, genParam))

            let generic = Expression.name "Generic"
            [ Expression.subscript (generic, Expression.tuple genParams) ]

    let private libReflectionCall (com: IPythonCompiler) ctx r memberName args =
        libCall com ctx r "reflection" (memberName + "_type") args

    let fableModuleAnnotation (com: IPythonCompiler) ctx moduleName memberName args =
        let expr = com.TransformImport(ctx, memberName, getLibPath com moduleName)

        match args with
        | [] -> expr
        | [ arg ] -> Expression.subscript (expr, arg)
        | args -> Expression.subscript (expr, Expression.tuple args)

    let stdlibModuleAnnotation (com: IPythonCompiler) ctx moduleName memberName args =
        let expr = com.TransformImport(ctx, memberName, moduleName)

        match memberName, args with
        | "Callable", args ->
            let returnType = List.last args

            let args =
                match args with
                | Expression.Name { Id = Identifier Ellipsis } :: _xs -> Expression.ellipsis
                | _ ->
                    args
                    |> List.removeAt (args.Length - 1)
                    |> List.choose (
                        function
                        | Expression.Name { Id = Identifier "None" } when args.Length = 2 -> None
                        | x -> Some x
                    )
                    |> Expression.list

            Expression.subscript (expr, Expression.tuple [ args; returnType ])
        | _, [] -> expr
        | _, [ arg ] -> Expression.subscript (expr, arg)
        | _, args -> Expression.subscript (expr, Expression.tuple args)

    let fableModuleTypeHint com ctx moduleName memberName genArgs repeatedGenerics =
        let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

        fableModuleAnnotation com ctx moduleName memberName resolved, stmts

    let stdlibModuleTypeHint com ctx moduleName memberName genArgs =
        let resolved, stmts = resolveGenerics com ctx genArgs None
        stdlibModuleAnnotation com ctx moduleName memberName resolved, stmts

    let makeGenTypeParamInst com ctx (genArgs: Fable.Type list) (repeatedGenerics: Set<string> option) =
        match genArgs with
        | [] -> []
        | _ -> genArgs |> List.map (typeAnnotation com ctx repeatedGenerics) |> List.map fst

    let makeGenericTypeAnnotation
        (com: IPythonCompiler)
        ctx
        (id: string)
        (genArgs: Fable.Type list)
        (repeatedGenerics: Set<string> option)
        =
        stdlibModuleAnnotation com ctx "__future__" "annotations" [] |> ignore

        let typeParamInst = makeGenTypeParamInst com ctx genArgs repeatedGenerics

        let name = Expression.name id

        if typeParamInst.IsEmpty then
            name
        else
            Expression.subscript (name, Expression.tuple typeParamInst)

    let makeGenericTypeAnnotation'
        (com: IPythonCompiler)
        ctx
        (id: string)
        (genArgs: string list)
        (repeatedGenerics: Set<string> option)
        =
        stdlibModuleAnnotation com ctx "__future__" "annotations" [] |> ignore

        let name = Expression.name id

        if genArgs.IsEmpty then
            name
        else
            let genArgs =
                match repeatedGenerics with
                | Some generics ->
                    let genArgs = genArgs |> Set.ofList |> Set.intersect generics |> Set.toList

                    if genArgs.IsEmpty then
                        [ stdlibModuleAnnotation com ctx "typing" "Any" [] ]
                    else
                        genArgs |> List.map (fun name -> com.AddTypeVar(ctx, name))
                | _ -> genArgs |> List.map (fun name -> com.AddTypeVar(ctx, name))

            Expression.subscript (name, Expression.tuple genArgs)

    let resolveGenerics com ctx generics repeatedGenerics : Expression list * Statement list =
        generics
        |> List.map (typeAnnotation com ctx repeatedGenerics)
        |> Helpers.unzipArgs

    let typeAnnotation
        (com: IPythonCompiler)
        ctx
        (repeatedGenerics: Set<string> option)
        (t: Fable.Type)
        : Expression * Statement list
        =
        // printfn "typeAnnotation: %A" (t, repeatedGenerics)
        match t with
        | Fable.Measure _
        | Fable.Any -> stdlibModuleTypeHint com ctx "typing" "Any" []
        | Fable.GenericParam(name = name) when name.StartsWith("$$", StringComparison.Ordinal) ->
            stdlibModuleTypeHint com ctx "typing" "Any" []
        | Fable.GenericParam(name = name) ->
            match repeatedGenerics with
            | Some names when names.Contains name ->
                let name = Helpers.clean name
                com.AddTypeVar(ctx, name), []
            | Some _ -> stdlibModuleTypeHint com ctx "typing" "Any" []
            | None ->
                let name = Helpers.clean name
                com.AddTypeVar(ctx, name), []
        | Fable.Unit -> Expression.none, []
        | Fable.Boolean -> Expression.name "bool", []
        | Fable.Char -> Expression.name "str", []
        | Fable.String -> Expression.name "str", []
        | Fable.Number(kind, info) -> makeNumberTypeAnnotation com ctx kind info
        | Fable.LambdaType(argType, returnType) ->
            let argTypes, returnType = uncurryLambdaType -1 [ argType ] returnType

            stdlibModuleTypeHint com ctx "collections.abc" "Callable" (argTypes @ [ returnType ])
        | Fable.DelegateType(argTypes, returnType) ->
            stdlibModuleTypeHint com ctx "collections.abc" "Callable" (argTypes @ [ returnType ])
        | Fable.Option(genArg, _) ->
            let resolved, stmts = resolveGenerics com ctx [ genArg ] repeatedGenerics

            Expression.binOp (resolved[0], BitOr, Expression.none), stmts
        | Fable.Tuple(genArgs, _) -> makeGenericTypeAnnotation com ctx "tuple" genArgs None, []
        | Fable.Array(genArg, _) ->
            match genArg with
            | Fable.Type.Number(UInt8, _) -> Expression.name "bytearray", []
            | Fable.Type.Number(Int8, _)
            | Fable.Type.Number(Int16, _)
            | Fable.Type.Number(UInt16, _)
            | Fable.Type.Number(Int32, _)
            | Fable.Type.Number(UInt32, _)
            | Fable.Type.Number(Float32, _)
            | Fable.Type.Number(Float64, _)
            | _ -> fableModuleTypeHint com ctx "types" "Array" [ genArg ] repeatedGenerics
        | Fable.List genArg -> fableModuleTypeHint com ctx "list" "FSharpList" [ genArg ] repeatedGenerics
        | Replacements.Util.Builtin kind -> makeBuiltinTypeAnnotation com ctx kind repeatedGenerics
        | Fable.AnonymousRecordType(_, _genArgs, _) ->
            let value = Expression.name "dict"
            let any, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            Expression.subscript (value, Expression.tuple [ Expression.name "str"; any ]), stmts
        | Fable.DeclaredType(entRef, genArgs) -> makeEntityTypeAnnotation com ctx entRef genArgs repeatedGenerics
        | _ -> stdlibModuleTypeHint com ctx "typing" "Any" []

    let makeNumberTypeAnnotation com ctx kind info =
        let numberInfo kind =
            let name =
                match kind with
                | Int8 -> "int8"
                | UInt8 -> "uint8"
                | Int16 -> "int16"
                | UInt16 -> "uint16"
                | UInt32 -> "uint32"
                | Int64 -> "int64"
                | UInt64 -> "uint64"
                | Int32
                | BigInt
                | Int128
                | UInt128
                | NativeInt
                | UNativeInt -> "int"
                | Float16
                | Float32 -> "float32"
                | Float64 -> "float"
                | _ -> failwith $"Unsupported number type: {kind}"

            match name with
            | "int"
            | "float" -> Expression.name name
            | _ -> fableModuleAnnotation com ctx "types" name []


        match kind, info with
        | _, Fable.NumberInfo.IsEnum entRef ->
            let ent = com.GetEntity(entRef)

            let cases =
                ent.FSharpFields
                |> Seq.choose (fun fi ->
                    match fi.Name with
                    | "value__" -> None
                    | name ->
                        let value =
                            match fi.LiteralValue with
                            | Some v -> Convert.ToDouble v
                            | None -> 0.

                        Expression.tuple [ Expression.stringConstant name; Expression.floatConstant value ]
                        |> Some
                )
                |> Seq.toList
                |> Expression.list

            [ Expression.stringConstant entRef.FullName; numberInfo kind; cases ]
            |> libReflectionCall com ctx None "enum",
            []
        | Decimal, _ -> stdlibModuleTypeHint com ctx "decimal" "Decimal" []
        | _ -> numberInfo kind, []

    let makeImportTypeId (com: IPythonCompiler) ctx moduleName typeName =
        let expr = com.GetImportExpr(ctx, getLibPath com moduleName, typeName)

        match expr with
        | Expression.Name { Id = Identifier id } -> id
        | _ -> typeName

    let makeImportTypeAnnotation com ctx genArgs moduleName typeName =
        let id = makeImportTypeId com ctx moduleName typeName
        makeGenericTypeAnnotation com ctx id genArgs None

    let makeEntityTypeAnnotation com ctx (entRef: Fable.EntityRef) genArgs repeatedGenerics =
        // printfn "DeclaredType: %A" entRef.FullName
        match entRef.FullName, genArgs with
        | Types.result, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "result" "FSharpResult_2" resolved, stmts
        | Replacements.Util.BuiltinEntity _kind -> stdlibModuleTypeHint com ctx "typing" "Any" []
        (*
            | Replacements.Util.BclGuid
            | Replacements.Util.BclTimeSpan
            | Replacements.Util.BclDateTime
            | Replacements.Util.BclDateTimeOffset
            | Replacements.Util.BclDateOnly
            | Replacements.Util.BclTimeOnly
            | Replacements.Util.BclTimer
            | Replacements.Util.BclBigInt -> genericEntity fullName [], []
            | Replacements.Util.BclHashSet gen
            | Replacements.Util.FSharpSet gen ->
                let gens, stmts = transformTypeInfo com ctx r genMap gen
                genericEntity fullName [ gens ], stmts
        | entName when entName.StartsWith(Types.choiceNonGeneric) ->
            makeUnionTypeAnnotation com ctx genArgs
            *)
        | Types.fsharpAsyncGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "async_builder" "Async" resolved, stmts
        | Types.taskGeneric, _ -> stdlibModuleTypeHint com ctx "typing" "Awaitable" genArgs
        | Types.icomparable, _ -> libValue com ctx "util" "IComparable", []
        | Types.iStructuralEquatable, _ -> libValue com ctx "util" "IStructuralEquatable", []
        | Types.iStructuralComparable, _ -> libValue com ctx "util" "IStructuralComparable", []
        | Types.icomparerGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "IComparer_1" resolved, stmts
        | Types.iequalityComparer, _ -> libValue com ctx "util" "IEqualityComparer", []
        | Types.iequalityComparerGeneric, _ ->
            let resolved, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            fableModuleAnnotation com ctx "util" "IEqualityComparer_1" [ resolved ], stmts
        | Types.ienumerator, _ ->
            let resolved, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            fableModuleAnnotation com ctx "util" "IEnumerator" [ resolved ], stmts
        | Types.ienumeratorGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "IEnumerator" resolved, stmts
        | Types.ienumerable, _ ->
            let resolved, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            fableModuleAnnotation com ctx "util" "IEnumerable" [ resolved ], stmts
        | Types.ienumerableGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "IEnumerable_1" resolved, stmts
        | Types.iequatableGeneric, _ ->
            let resolved, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            fableModuleAnnotation com ctx "util" "IEquatable" [ resolved ], stmts
        | Types.icomparableGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "IComparable_1" resolved, stmts
        | Types.icollection, _
        | Types.icollectionGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "ICollection" resolved, stmts
        | Types.idisposable, _ -> libValue com ctx "util" "IDisposable", []
        | Types.iobserverGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "observable" "IObserver" resolved, stmts
        | Types.iobservableGeneric, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "observable" "IObservable" resolved, stmts
        | Types.idictionary, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "util" "IDictionary" resolved, stmts
        | Types.ievent2, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "event" "IEvent_2" resolved, stmts
        | Types.cancellationToken, _ -> libValue com ctx "async_builder" "CancellationToken", []
        | Types.mailboxProcessor, _ ->
            let resolved, stmts = resolveGenerics com ctx genArgs repeatedGenerics

            fableModuleAnnotation com ctx "mailbox_processor" "MailboxProcessor" resolved, stmts
        | "Fable.Core.Py.Callable", _ ->
            let any, stmts = stdlibModuleTypeHint com ctx "typing" "Any" []

            let genArgs = [ Expression.ellipsis; any ]

            stdlibModuleAnnotation com ctx "collections.abc" "Callable" genArgs, stmts
        | _ ->
            let ent = com.GetEntity(entRef)
            // printfn "DeclaredType: %A" ent.FullName
            if ent.IsInterface then
                let name = Helpers.removeNamespace ent.FullName

                // If the interface is imported then it's erased and we need to add the actual imports
                match ent.Attributes with
                | FSharp2Fable.Util.ImportAtt(name, importPath) -> com.GetImportExpr(ctx, importPath, name) |> ignore
                | _ ->
                    match entRef.SourcePath with
                    | Some path when path <> com.CurrentFile ->
                        // this is just to import the interface
                        let importPath = Path.getRelativeFileOrDirPath false com.CurrentFile false path

                        com.GetImportExpr(ctx, importPath, name) |> ignore
                    | _ -> ()

                makeGenericTypeAnnotation com ctx name genArgs repeatedGenerics, []
            else
                match tryPyConstructor com ctx ent with
                | Some(entRef, stmts) ->
                    match entRef with
                    (*
                    | Literal(Literal.StringLiteral(StringLiteral(str, _))) ->
                        match str with
                        | "number" -> NumberTypeAnnotation
                        | "boolean" -> BooleanTypeAnnotation
                        | "string" -> StringTypeAnnotation
                        | _ -> AnyTypeAnnotation*)
                    | Expression.Name { Id = Identifier id } ->
                        makeGenericTypeAnnotation com ctx id genArgs repeatedGenerics, stmts
                    // TODO: Resolve references to types in nested modules
                    | _ -> stdlibModuleTypeHint com ctx "typing" "Any" []
                | None -> stdlibModuleTypeHint com ctx "typing" "Any" []

    let makeBuiltinTypeAnnotation com ctx kind repeatedGenerics =
        match kind with
        | Replacements.Util.BclGuid -> Expression.name "str", []
        | Replacements.Util.FSharpReference genArg ->
            makeImportTypeAnnotation com ctx [ genArg ] "types" "FSharpRef", []
        (*
        | Replacements.Util.BclTimeSpan -> NumberTypeAnnotation
        | Replacements.Util.BclDateTime -> makeSimpleTypeAnnotation com ctx "Date"
        | Replacements.Util.BclDateTimeOffset -> makeSimpleTypeAnnotation com ctx "Date"
        | Replacements.Util.BclDateOnly -> makeSimpleTypeAnnotation com ctx "Date"
        | Replacements.Util.BclTimeOnly -> NumberTypeAnnotation
        | Replacements.Util.BclTimer -> makeImportTypeAnnotation com ctx [] "Timer" "Timer"
        | Replacements.Util.BclDecimal -> makeImportTypeAnnotation com ctx [] "Decimal" "decimal"
        | Replacements.Util.BclBigInt -> makeImportTypeAnnotation com ctx [] "BigInt/z" "BigInteger"
        | Replacements.Util.BclHashSet key -> makeNativeTypeAnnotation com ctx [key] "Set"
        | Replacements.Util.BclDictionary (key, value) -> makeNativeTypeAnnotation com ctx [key; value] "Map"
        | Replacements.Util.BclKeyValuePair (key, value) -> makeTupleTypeAnnotation com ctx [key; value]
        | Replacements.Util.FSharpSet key -> makeImportTypeAnnotation com ctx [key] "Set" "FSharpSet"
        | Replacements.Util.FSharpMap (key, value) -> makeImportTypeAnnotation com ctx [key; value] "Map" "FSharpMap"
        | Replacements.Util.FSharpChoice genArgs ->
            $"FSharpChoice${List.length genArgs}"
            |> makeImportTypeAnnotation com ctx genArgs "Fable.Core"
        *)
        | Replacements.Util.FSharpResult(ok, err) ->
            let resolved, stmts = resolveGenerics com ctx [ ok; err ] repeatedGenerics

            fableModuleAnnotation com ctx "result" "FSharpResult_2" resolved, stmts
        | _ -> stdlibModuleTypeHint com ctx "typing" "Any" []

    let transformFunctionWithAnnotations (com: IPythonCompiler) ctx name (args: Fable.Ident list) (body: Fable.Expr) =
        let argTypes = args |> List.map (fun id -> id.Type)

        // In Python a generic type arg must appear both in the argument and the return type (cannot appear only once)
        let repeatedGenerics =
            Util.getRepeatedGenericTypeParams ctx (argTypes @ [ body.Type ])

        let args', body' = com.TransformFunction(ctx, name, args, body, repeatedGenerics)

        let returnType, stmts = typeAnnotation com ctx (Some repeatedGenerics) body.Type

        // If the only argument is generic, then we make the return type optional as well
        let returnType' =
            // printfn "Generic params: %A" (args, repeatedGenerics, body.Type)
            match args, body.Type with
            | [ { Type = Fable.GenericParam(name = x) } ], Fable.GenericParam(name = y) when
                x = y && Set.contains x repeatedGenerics
                ->
                Expression.binOp (returnType, BinaryOrBitwise, Expression.none)
            | _ -> returnType

        args', stmts @ body', returnType'

module Util =
    open Lib
    open Reflection
    open Annotation

    let getIdentifier (_com: IPythonCompiler) (_ctx: Context) (name: string) =
        let name = Helpers.clean name
        Identifier name

    let (|TransformExpr|) (com: IPythonCompiler) ctx e : Expression * Statement list = com.TransformAsExpr(ctx, e)

    let (|Function|_|) =
        function
        | Fable.Lambda(arg, body, _) -> Some([ arg ], body)
        | Fable.Delegate(args, body, _, []) -> Some(args, body)
        | _ -> None

    let getUniqueNameInRootScope (ctx: Context) name =
        let name =
            (name, Naming.NoMemberPart)
            ||> Naming.sanitizeIdent (fun name ->
                name <> "str" // Do not rewrite `str`
                && (ctx.UsedNames.RootScope.Contains(name)
                    || ctx.UsedNames.DeclarationScopes.Contains(name))
            )

        ctx.UsedNames.RootScope.Add(name) |> ignore
        Helpers.clean name

    let getUniqueNameInDeclarationScope (ctx: Context) name =
        let name =
            (name, Naming.NoMemberPart)
            ||> Naming.sanitizeIdent (fun name ->
                ctx.UsedNames.RootScope.Contains(name)
                || ctx.UsedNames.CurrentDeclarationScope.Contains(name)
            )

        ctx.UsedNames.CurrentDeclarationScope.Add(name) |> ignore

        name

    type NamedTailCallOpportunity(com: IPythonCompiler, ctx, name, args: Fable.Ident list) =
        // Capture the current argument values to prevent delayed references from getting corrupted,
        // for that we use block-scoped ES2015 variable declarations. See #681, #1859
        // TODO: Local unique ident names
        let argIds =
            args
            |> FSharp2Fable.Util.discardUnitArg
            |> List.map (fun arg ->
                let name = getUniqueNameInDeclarationScope ctx (arg.Name + "_mut")
                // Ignore type annotation here as it generates unnecessary typevars
                Arg.arg name
            )

        interface ITailCallOpportunity with
            member _.Label = name
            member _.Args = argIds

            member _.IsRecursiveRef(e) =
                match e with
                | Fable.IdentExpr id -> name = id.Name
                | _ -> false

    let getDecisionTarget (ctx: Context) targetIndex =
        match List.tryItem targetIndex ctx.DecisionTargets with
        | None -> failwith $"Cannot find DecisionTree target %i{targetIndex}"
        | Some(idents, target) -> idents, target

    let rec isPyStatement ctx preferStatement (expr: Fable.Expr) =
        match expr with
        | Fable.Unresolved _
        | Fable.Value _
        | Fable.Import _
        | Fable.IdentExpr _
        | Fable.Lambda _
        | Fable.Delegate _
        | Fable.ObjectExpr _
        | Fable.Call _
        | Fable.CurriedApply _
        | Fable.Operation _
        | Fable.Get _
        | Fable.Test _
        | Fable.TypeCast _ -> false

        | Fable.TryCatch _
        | Fable.Sequential _
        | Fable.Let _
        | Fable.LetRec _
        | Fable.Set _
        | Fable.ForLoop _
        | Fable.WhileLoop _ -> true
        | Fable.Extended(kind, _) ->
            match kind with
            | Fable.Throw _
            | Fable.Debugger -> true
            | Fable.Curry _ -> false

        // TODO: If IsJsSatement is false, still try to infer it? See #2414
        // /^\s*(break|continue|debugger|while|for|switch|if|try|let|const|var)\b/
        | Fable.Emit(i, _, _) -> i.IsStatement

        | Fable.DecisionTreeSuccess(targetIndex, _, _) ->
            getDecisionTarget ctx targetIndex |> snd |> isPyStatement ctx preferStatement

        // Make it also statement if we have more than, say, 3 targets?
        // That would increase the chances to convert it into a switch
        | Fable.DecisionTree(_, targets) -> preferStatement || List.exists (snd >> (isPyStatement ctx false)) targets

        | Fable.IfThenElse(_, thenExpr, elseExpr, _) ->
            preferStatement
            || isPyStatement ctx false thenExpr
            || isPyStatement ctx false elseExpr

    let addErrorAndReturnNull (com: Compiler) (range: SourceLocation option) (error: string) =
        addError com [] range error
        Expression.none

    let ident (com: IPythonCompiler) (ctx: Context) (id: Fable.Ident) = com.GetIdentifier(ctx, id.Name)

    let identAsExpr (com: IPythonCompiler) (ctx: Context) (id: Fable.Ident) =
        com.GetIdentifierAsExpr(ctx, Naming.toSnakeCase id.Name)

    let thisExpr = Expression.name "self"

    let ofInt (i: int) = Expression.intConstant (int i)

    let ofString (s: string) = Expression.stringConstant s

    let memberFromName (_com: IPythonCompiler) (_ctx: Context) (memberName: string) : Expression =
        // printfn "memberFromName: %A" memberName
        match memberName with
        | "ToString" -> Expression.identifier "__str__"
        | "GetHashCode" -> Expression.identifier "__hash__"
        | "Equals" -> Expression.identifier "__eq__"
        | "CompareTo" -> Expression.identifier "__cmp__"
        | "set" -> Expression.identifier "__setitem__"
        | "get" -> Expression.identifier "__getitem__"
        | "has" -> Expression.identifier "__contains__"
        | "delete" -> Expression.identifier "__delitem__"
        | n when n.EndsWith("get_Count", StringComparison.Ordinal) -> Expression.identifier "__len__" // TODO: find a better way
        | n when n.StartsWith("Symbol.iterator", StringComparison.Ordinal) ->
            let name = Identifier "__iter__"
            Expression.name name
        | n ->
            let n = Naming.toSnakeCase n

            (n, Naming.NoMemberPart)
            ||> Naming.sanitizeIdent (fun _ -> false)
            |> Expression.name

    let get (com: IPythonCompiler) ctx _r left memberName subscript =
        // printfn "get: %A" (memberName, subscript)
        match subscript with
        | true ->
            let expr = Expression.stringConstant memberName
            Expression.subscript (value = left, slice = expr, ctx = Load)
        | _ ->
            let expr = com.GetIdentifier(ctx, memberName)
            Expression.attribute (value = left, attr = expr, ctx = Load)

    let getExpr _com _ctx _r (object: Expression) (expr: Expression) =
        match expr with
        | Expression.Constant(value = StringLiteral name) ->
            let name = name |> Identifier
            Expression.attribute (value = object, attr = name, ctx = Load), []
        | e -> Expression.subscript (value = object, slice = e, ctx = Load), []

    let rec getParts com ctx (parts: string list) (expr: Expression) =
        match parts with
        | [] -> expr
        | m :: ms -> get com ctx None expr m false |> getParts com ctx ms

    let makeArray (com: IPythonCompiler) ctx exprs kind typ : Expression * Statement list =
        //printfn "makeArray: %A" (exprs, kind, typ)
        let expr, stmts =
            exprs |> List.map (fun e -> com.TransformAsExpr(ctx, e)) |> Helpers.unzipArgs

        let letter =
            match kind, typ with
            | Fable.ResizeArray, _ -> None
            | _, Fable.Type.Number(UInt8, _) -> Some "B"
            | _, Fable.Type.Number(Int8, _) -> Some "b"
            | _, Fable.Type.Number(Int16, _) -> Some "h"
            | _, Fable.Type.Number(UInt16, _) -> Some "H"
            | _, Fable.Type.Number(Int32, _) -> Some "l"
            | _, Fable.Type.Number(UInt32, _) -> Some "L"
            | _, Fable.Type.Number(Int64, _) -> Some "q"
            | _, Fable.Type.Number(UInt64, _) -> Some "Q"
            | _, Fable.Type.Number(Float32, _) -> Some "f"
            | _, Fable.Type.Number(Float64, _) -> Some "d"
            | _ -> None

        match letter with
        | Some "B" ->
            let bytearray = Expression.name "bytearray"
            Expression.call (bytearray, [ Expression.list expr ]), stmts
        | Some l ->
            let array = com.GetImportExpr(ctx, "array", "array")

            Expression.call (array, Expression.stringConstant l :: [ Expression.list expr ]), stmts
        | _ -> expr |> Expression.list, stmts


    let makeArrayAllocated (com: IPythonCompiler) ctx _typ _kind (size: Fable.Expr) =
        //printfn "makeArrayAllocated"
        let size, stmts = com.TransformAsExpr(ctx, size)
        let array = Expression.list [ Expression.intConstant 0 ]
        Expression.binOp (array, Mult, size), stmts

    let makeArrayFrom (com: IPythonCompiler) ctx typ kind (fableExpr: Fable.Expr) : Expression * Statement list =
        match fableExpr with
        | Replacements.Util.ArrayOrListLiteral(exprs, _) -> makeArray com ctx exprs kind typ
        | _ ->
            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)
            let name = Expression.name "list"
            Expression.call (name, [ expr ]), stmts

    let makeList (com: IPythonCompiler) ctx exprs =
        let expr, stmts =
            exprs |> List.map (fun e -> com.TransformAsExpr(ctx, e)) |> Helpers.unzipArgs

        expr |> Expression.list, stmts

    let makeTuple (com: IPythonCompiler) ctx exprs =
        let expr, stmts =
            exprs |> List.map (fun e -> com.TransformAsExpr(ctx, e)) |> Helpers.unzipArgs

        expr |> Expression.tuple, stmts

    let makeStringArray strings =
        strings |> List.map (fun x -> Expression.stringConstant x) |> Expression.list

    let makePyObject (pairs: seq<string * Expression>) =
        pairs
        |> Seq.map (fun (name, value) ->
            let prop = Expression.stringConstant name
            prop, value
        )
        |> Seq.toList
        |> List.unzip
        |> Expression.dict

    let assign range left right =
        Expression.namedExpr (left, right, ?loc = range)

    /// Immediately Invoked Function Expression
    let iife (com: IPythonCompiler) ctx (expr: Fable.Expr) =
        let afe, stmts =
            transformFunctionWithAnnotations com ctx None [] expr
            |||> makeArrowFunctionExpression com ctx None

        Expression.call (afe, []), stmts

    let multiVarDeclaration (ctx: Context) (variables: (Identifier * Expression option) list) =
        // printfn "multiVarDeclaration: %A" (variables)
        let ids, values =
            variables
            |> List.distinctBy (fun (Identifier(name = name), _value) -> name)
            |> List.map (
                function
                | i, Some value -> Expression.name (i, Store), value, i
                | i, _ -> Expression.name (i, Store), Expression.none, i
            )
            |> List.unzip3
            |> fun (ids, values, ids') ->
                ctx.BoundVars.Bind(ids')
                (Expression.tuple ids, Expression.tuple values)

        [ Statement.assign ([ ids ], values) ]

    let varDeclaration (ctx: Context) (var: Expression) (typ: Expression option) value =
        // printfn "varDeclaration: %A" (var, value, typ)
        match var with
        | Name { Id = id } -> do ctx.BoundVars.Bind([ id ])
        | _ -> ()

        [
            match typ with
            | Some typ -> Statement.assign (var, annotation = typ, value = value)
            | _ -> Statement.assign ([ var ], value)
        ]

    let restElement (var: Identifier) =
        let var = Expression.name var
        Expression.starred var

    let callSuper (args: Expression list) =
        let super = Expression.name "super().__init__"
        Expression.call (super, args)

    let callSuperAsStatement (args: Expression list) = Statement.expr (callSuper args)

    let makeClassConstructor (args: Arguments) (isOptional: bool) body =
        // printfn "makeClassConstructor: %A" (args.Args, body)
        let name = Identifier("__init__")
        let self = Arg.arg "self"

        let args_ =
            match args.Args with
            | [ _unit ] when isOptional ->
                { args with
                    Args = self :: args.Args
                    Defaults = [ Expression.none ]
                }
            | _ -> { args with Args = self :: args.Args }

        match args.Args, body with
        | [], []
        | [], [ Statement.Pass ] -> [] // Remove empty `__init__` with no arguments
        | _ -> [ Statement.functionDef (name, args_, body = body, returns = Expression.none) ]

    let callFunction r funcExpr (args: Expression list) (kw: Keyword list) =
        Expression.call (funcExpr, args, kw = kw, ?loc = r)

    let callFunctionWithThisContext com ctx r funcExpr (args: Expression list) =
        let args = thisExpr :: args
        Expression.call (get com ctx None funcExpr "call" false, args, ?loc = r)

    let emitExpression range (txt: string) args =
        let value =
            match txt with
            | "$0.join('')" -> "''.join($0)"
            | "throw $0" -> "raise $0"
            | Naming.StartsWith "void " value
            | Naming.StartsWith "new " value -> value
            | _ -> txt

        Expression.emit (value, args, ?loc = range)

    let undefined _range : Expression = Expression.none

    let getGenericTypeParams (types: Fable.Type list) =
        types |> FSharp2Fable.Util.getGenParamNames |> Set.ofList

    // Returns type parameters that is used more than once
    let getRepeatedGenericTypeParams ctx (types: Fable.Type list) =
        types
        |> FSharp2Fable.Util.getGenParamNames
        |> List.append (ctx.ScopedTypeParams |> Set.toList)
        |> List.countBy id
        |> List.choose (fun (param, count) ->
            if count > 1 then
                Some param
            else
                None
        )
        |> Set.ofList

    type MemberKind =
        | ClassConstructor
        | NonAttached of funcName: string
        | Attached of isStatic: bool

    let getMemberArgsAndBody (com: IPythonCompiler) ctx kind hasSpread (args: Fable.Ident list) (body: Fable.Expr) =
        // printfn "getMemberArgsAndBody: %A" hasSpread
        let funcName, genTypeParams, args, body =
            match kind, args with
            | Attached(isStatic = false), thisArg :: args ->
                let genTypeParams =
                    Set.difference (getGenericTypeParams [ thisArg.Type ]) ctx.ScopedTypeParams

                let body =
                    // TODO: If ident is not captured maybe we can just replace it with "this"
                    if isIdentUsed thisArg.Name body then
                        let thisKeyword = Fable.IdentExpr { thisArg with Name = "self" }

                        Fable.Let(thisArg, thisKeyword, body)
                    else
                        body

                None, genTypeParams, args, body
            | Attached(isStatic = true), _
            | ClassConstructor, _ -> None, ctx.ScopedTypeParams, args, body
            | NonAttached funcName, _ -> Some funcName, Set.empty, args, body
            | _ -> None, Set.empty, args, body

        let ctx =
            { ctx with ScopedTypeParams = Set.union ctx.ScopedTypeParams genTypeParams }

        let args, body, returnType =
            transformFunctionWithAnnotations com ctx funcName args body

        let args =
            let len = args.Args.Length

            if not hasSpread || len = 0 then
                args
            else
                { args with
                    VarArg = Some { args.Args[len - 1] with Annotation = None }
                    Args = args.Args[.. len - 2]
                }

        args, body, returnType

    let getUnionCaseName (uci: Fable.UnionCase) =
        match uci.CompiledName with
        | Some cname -> cname
        | None -> uci.Name

    let getUnionExprTag (com: IPythonCompiler) ctx r (fableExpr: Fable.Expr) =
        let expr, stmts = com.TransformAsExpr(ctx, fableExpr)

        let expr, stmts' = getExpr com ctx r expr (Expression.stringConstant "tag")

        expr, stmts @ stmts'

    let wrapIntExpression typ (e: Expression) =
        match e, typ with
        | Expression.Constant _, _ -> e
        // TODO: Unsigned ints seem to cause problems, should we check only Int32 here?
        | _, Fable.Number((Int8 | Int16 | Int32), _) ->
            Expression.boolOp (BoolOperator.Or, [ e; Expression.intConstant 0 ])
        | _ -> e

    let wrapExprInBlockWithReturn (e, stmts) = stmts @ [ Statement.return' e ]

    let makeArrowFunctionExpression
        com
        ctx
        (name: string option)
        (args: Arguments)
        (body: Statement list)
        returnType
        : Expression * Statement list
        =

        let args =
            match args.Args with
            | [] ->
                let ta = com.GetImportExpr(ctx, "typing", "Any")

                Arguments.arguments (args = [ Arg.arg ("__unit", annotation = ta) ], defaults = [ Expression.none ])
            | _ -> args

        let allDefaultsAreNone =
            args.Defaults
            |> List.forall (
                function
                | Expression.Name { Id = Identifier "None" } -> true
                | _ -> false
            )

        let (|ImmediatelyApplied|_|) =
            function
            | Expression.Call {
                                  Func = callee
                                  Args = appliedArgs
                              } when args.Args.Length = appliedArgs.Length && allDefaultsAreNone ->
                // To be sure we're not running side effects when deleting the function check the callee is an identifier
                match callee with
                | Expression.Name _ ->
                    let parameters = args.Args |> List.map (fun a -> (Expression.name a.Arg))

                    List.zip parameters appliedArgs
                    |> List.forall (
                        function
                        | Expression.Name({ Id = Identifier name1 }), Expression.Name({ Id = Identifier name2 }) ->
                            name1 = name2
                        | _ -> false
                    )
                    |> function
                        | true -> Some callee
                        | false -> None
                | _ -> None
            | _ -> None

        match body with
        // Check if we can remove the function
        | [ Statement.Return { Value = Some(ImmediatelyApplied(callExpr)) } ] -> callExpr, []
        | _ ->
            let ident =
                name
                |> Option.map Identifier
                |> Option.defaultWith (fun _ -> Helpers.getUniqueIdentifier "_arrow")

            let func = createFunction ident args body [] returnType None
            Expression.name ident, [ func ]

    let createFunction name args body decoratorList returnType (comment: string option) =
        let (|Awaitable|_|) expr =
            match expr with
            | Expression.Call {
                                  Func = Expression.Attribute {
                                                                  Value = Expression.Name { Id = Identifier "_builder" }
                                                                  Attr = Identifier "Run"
                                                              }
                              } -> Some expr
            | _ -> None

        let isAsync =
            // function is async is returnType is an Awaitable and the body return a call to _builder.Run
            match returnType with
            | Subscript { Value = Name { Id = Identifier "Awaitable" } } ->
                let rec find body : bool =
                    body
                    |> List.tryFind (
                        function
                        | Statement.Return {
                                               Value = Some(Expression.IfExp {
                                                                                 Body = Awaitable _
                                                                                 OrElse = Awaitable _
                                                                             })
                                           } -> true
                        | Statement.Return { Value = Some(Awaitable _) } -> true
                        | Statement.If {
                                           Body = body
                                           Else = orElse
                                       } -> find body && find orElse
                        | _stmt -> false
                    )
                    |> Option.isSome

                find body
            | _ -> false

        let rec replace body : Statement list =
            body
            |> List.map (
                function
                | Statement.Return {
                                       Value = Some(Expression.IfExp {
                                                                         Test = test
                                                                         Body = body
                                                                         OrElse = orElse
                                                                     })
                                   } ->
                    Statement.return' (Expression.ifExp (test, Expression.Await(body), Expression.Await(orElse)))
                | Statement.Return { Value = Some(Awaitable(expr)) } -> Statement.return' (Expression.Await expr)
                | Statement.If {
                                   Test = test
                                   Body = body
                                   Else = orElse
                               } -> Statement.if' (test, replace body, orelse = replace orElse)
                | stmt -> stmt
            )

        match isAsync, returnType with
        | true, Subscript { Slice = returnType } ->
            let body' = replace body

            Statement.asyncFunctionDef (
                name = name,
                args = args,
                body = body',
                decoratorList = decoratorList,
                returns = returnType,
                ?comment = comment
            )
        | _ ->
            Statement.functionDef (
                name = name,
                args = args,
                body = body,
                decoratorList = decoratorList,
                returns = returnType,
                ?comment = comment
            )

    let makeFunction name (args: Arguments, body: Expression, decoratorList, returnType) : Statement =
        // printfn "makeFunction: %A" name
        let body = wrapExprInBlockWithReturn (body, [])
        createFunction name args body decoratorList returnType None

    let makeFunctionExpression
        (com: IPythonCompiler)
        ctx
        name
        (args, body: Expression, decoratorList, returnType: Expression)
        : Expression * Statement list
        =
        let ctx = { ctx with BoundVars = ctx.BoundVars.EnterScope() }

        let name =
            name
            |> Option.map (fun name -> com.GetIdentifier(ctx, name))
            |> Option.defaultValue (Helpers.getUniqueIdentifier "_expr")

        let func = makeFunction name (args, body, decoratorList, returnType)
        Expression.name name, [ func ]

    let optimizeTailCall (com: IPythonCompiler) (ctx: Context) range (tc: ITailCallOpportunity) args =
        let rec checkCrossRefs tempVars allArgs =
            function
            | [] -> tempVars
            | (argId, _arg) :: rest ->
                let found =
                    allArgs
                    |> List.exists (
                        deepExists (
                            function
                            | Fable.IdentExpr i -> argId = i.Name
                            | _ -> false
                        )
                    )

                let tempVars =
                    if found then
                        let tempVarName = getUniqueNameInDeclarationScope ctx (argId + "_tmp")

                        Map.add argId tempVarName tempVars
                    else
                        tempVars

                checkCrossRefs tempVars allArgs rest

        ctx.OptimizeTailCall()

        let zippedArgs =
            List.zip (tc.Args |> List.map (fun { Arg = Identifier id } -> id)) args

        let tempVars = checkCrossRefs Map.empty args zippedArgs

        let tempVarReplacements = tempVars |> Map.map (fun _ v -> makeIdentExpr v)

        [
            // First declare temp variables
            for KeyValue(argId, tempVar) in tempVars do
                yield!
                    varDeclaration
                        ctx
                        (com.GetIdentifierAsExpr(ctx, tempVar))
                        None
                        (com.GetIdentifierAsExpr(ctx, argId))
            // Then assign argument expressions to the original argument identifiers
            // See https://github.com/fable-compiler/Fable/issues/1368#issuecomment-434142713
            for argId, arg in zippedArgs do
                let arg = FableTransforms.replaceValues tempVarReplacements arg
                let arg, stmts = com.TransformAsExpr(ctx, arg)

                yield!
                    stmts
                    @ (assign None (com.GetIdentifierAsExpr(ctx, argId)) arg |> exprAsStatement ctx)
            yield Statement.continue' (?loc = range)
        ]

    let transformImport (com: IPythonCompiler) ctx (_r: SourceLocation option) (name: string) (moduleName: string) =
        let name, parts =
            let parts = Array.toList (name.Split('.'))
            parts.Head, parts.Tail

        com.GetImportExpr(ctx, moduleName, name) |> getParts com ctx parts

    let transformCast (com: IPythonCompiler) (ctx: Context) t e : Expression * Statement list =
        match t with
        // Optimization for (numeric) array or list literals casted to seq
        // Done at the very end of the compile pipeline to get more opportunities
        // of matching cast and literal expressions after resolving pipes, inlining...
        | Fable.DeclaredType(ent, [ _ ]) ->
            match ent.FullName, e with
            | Types.ienumerableGeneric, Replacements.Util.ArrayOrListLiteral(exprs, _typ) ->
                let expr, stmts =
                    exprs |> List.map (fun e -> com.TransformAsExpr(ctx, e)) |> Helpers.unzipArgs

                let xs = Expression.list expr
                libCall com ctx None "util" "to_enumerable" [ xs ], stmts

            | _ -> com.TransformAsExpr(ctx, e)
        | _ -> com.TransformAsExpr(ctx, e)

    let transformCurry (com: IPythonCompiler) (ctx: Context) expr arity : Expression * Statement list =
        com.TransformAsExpr(ctx, Replacements.Api.curryExprAtRuntime com arity expr)

    let makeInteger (com: IPythonCompiler) (ctx: Context) r _t intName (x: obj) =
        let cons = libValue com ctx "types" intName
        let value = Expression.intConstant (x, ?loc = r)
        Expression.call (cons, [ value ], ?loc = r), []

    let makeFloat (com: IPythonCompiler) (ctx: Context) r _t floatName x =
        let cons = libValue com ctx "types" floatName
        let value = Expression.floatConstant (x, ?loc = r)
        Expression.call (cons, [ value ], ?loc = r), []

    let transformValue (com: IPythonCompiler) (ctx: Context) r value : Expression * Statement list =
        match value with
        | Fable.BaseValue(None, _) -> Expression.identifier "super()", []
        | Fable.BaseValue(Some boundIdent, _) -> identAsExpr com ctx boundIdent, []
        | Fable.ThisValue _ -> Expression.identifier "self", []
        | Fable.TypeInfo(t, _) -> transformTypeInfo com ctx r Map.empty t
        | Fable.Null _t -> Expression.none, []
        | Fable.UnitConstant -> undefined r, []
        | Fable.BoolConstant x -> Expression.boolConstant (x, ?loc = r), []
        | Fable.CharConstant x -> Expression.stringConstant (string<char> x, ?loc = r), []
        | Fable.StringConstant x -> Expression.stringConstant (x, ?loc = r), []
        | Fable.StringTemplate(_, parts, values) ->
            match parts with
            | [] -> makeStrConst ""
            | [ part ] -> makeStrConst part
            | part :: parts ->
                let acc = makeStrConst part

                (acc, List.zip values parts)
                ||> List.fold (fun acc (MaybeCasted(value), part) ->
                    let value =
                        match value.Type with
                        | Fable.String -> value
                        | _ -> Helpers.toString value

                    let acc = makeBinOp None Fable.String acc value BinaryPlus

                    makeBinOp None Fable.String acc (makeStrConst part) BinaryPlus
                )
            |> transformAsExpr com ctx
        | Fable.NumberConstant(v, _) ->
            match v with
            | Fable.NumberValue.Int8 x -> makeInteger com ctx r value.Type "int8" x
            | Fable.NumberValue.UInt8 x -> makeInteger com ctx r value.Type "uint8" x
            | Fable.NumberValue.Int16 x -> makeInteger com ctx r value.Type "int16" x
            | Fable.NumberValue.UInt16 x -> makeInteger com ctx r value.Type "uint16" x
            | Fable.NumberValue.Int32 x -> Expression.intConstant (x, ?loc = r), []
            | Fable.NumberValue.UInt32 x -> makeInteger com ctx r value.Type "uint32" x
            | Fable.NumberValue.Int64 x -> makeInteger com ctx r value.Type "int64" x
            | Fable.NumberValue.UInt64 x -> makeInteger com ctx r value.Type "uint64" x
            // | Fable.NumberValue.Int128(u,l) -> Expression.intConstant (System.Int128(u,l), ?loc = r), []
            // | Fable.NumberValue.UInt128(u,l) -> Expression.intConstant (System.UInt128(u,l), ?loc = r), []
            | Fable.NumberValue.BigInt x -> Expression.intConstant (x, ?loc = r), []
            | Fable.NumberValue.NativeInt x -> Expression.intConstant (x, ?loc = r), []
            | Fable.NumberValue.UNativeInt x -> Expression.intConstant (x, ?loc = r), []
            // TODO: special consts also need attention
            | Fable.NumberValue.Float64 x when x = infinity -> Expression.name "float('inf')", []
            | Fable.NumberValue.Float64 x when x = -infinity -> Expression.name "float('-inf')", []
            | Fable.NumberValue.Float64 x when Double.IsNaN(x) -> Expression.name "float('nan')", []
            | Fable.NumberValue.Float32 x when Single.IsNaN(x) ->
                libCall com ctx r "types" "float32" [ Expression.stringConstant "nan" ], []
            | Fable.NumberValue.Float16 x when Single.IsNaN(x) ->
                libCall com ctx r "types" "float32" [ Expression.stringConstant "nan" ], []
            | Fable.NumberValue.Float16 x -> makeFloat com ctx r value.Type "float32" (float x)
            | Fable.NumberValue.Float32 x -> makeFloat com ctx r value.Type "float32" (float x)
            | Fable.NumberValue.Float64 x -> Expression.floatConstant (x, ?loc = r), []
            | Fable.NumberValue.Decimal x -> Py.Replacements.makeDecimal com r value.Type x |> transformAsExpr com ctx
            | _ -> addErrorAndReturnNull com r $"Numeric literal is not supported: %A{v}", []
        | Fable.NewArray(newKind, typ, kind) ->
            match newKind with
            | Fable.ArrayValues values -> makeArray com ctx values kind typ
            | Fable.ArrayAlloc size -> makeArrayAllocated com ctx typ kind size
            | Fable.ArrayFrom expr -> makeArrayFrom com ctx typ kind expr

        | Fable.NewTuple(vals, _) -> makeTuple com ctx vals
        // Optimization for bundle size: compile list literals as List.ofArray
        | Fable.NewList(headAndTail, _) ->
            let rec getItems acc =
                function
                | None -> List.rev acc, None
                | Some(head, Fable.Value(Fable.NewList(tail, _), _)) -> getItems (head :: acc) tail
                | Some(head, tail) -> List.rev (head :: acc), Some tail

            match getItems [] headAndTail with
            | [], None -> libCall com ctx r "list" "empty" [], []
            | [ TransformExpr com ctx (expr, stmts) ], None -> libCall com ctx r "list" "singleton" [ expr ], stmts
            | exprs, None ->
                let expr, stmts = makeList com ctx exprs
                [ expr ] |> libCall com ctx r "list" "ofArray", stmts
            | [ TransformExpr com ctx (head, stmts) ], Some(TransformExpr com ctx (tail, stmts')) ->
                libCall com ctx r "list" "cons" [ head; tail ], stmts @ stmts'
            | exprs, Some(TransformExpr com ctx (tail, stmts)) ->
                let expr, stmts' = makeList com ctx exprs

                [ expr; tail ] |> libCall com ctx r "list" "ofArrayWithTail", stmts @ stmts'
        | Fable.NewOption(value, t, _) ->
            match value with
            | Some(TransformExpr com ctx (e, stmts)) ->
                if mustWrapOption t then
                    libCall com ctx r "option" "some" [ e ], stmts
                else
                    e, stmts
            | None -> undefined r, []
        | Fable.NewRecord(values, ent, _genArgs) ->
            let ent = com.GetEntity(ent)

            let values, stmts =
                List.map (fun x -> com.TransformAsExpr(ctx, x)) values |> Helpers.unzipArgs

            let consRef, stmts' = ent |> pyConstructor com ctx
            Expression.call (consRef, values, ?loc = r), stmts @ stmts'
        | Fable.NewAnonymousRecord(values, fieldNames, _genArgs, _isStruct) ->
            let values, stmts =
                values |> List.map (fun x -> com.TransformAsExpr(ctx, x)) |> Helpers.unzipArgs

            List.zip (List.ofArray fieldNames) values |> makePyObject, stmts
        | Fable.NewUnion(values, tag, ent, _genArgs) ->
            let ent = com.GetEntity(ent)

            let values, stmts =
                List.map (fun x -> com.TransformAsExpr(ctx, x)) values |> Helpers.unzipArgs

            let consRef, stmts' = ent |> pyConstructor com ctx
            // let caseName = ent.UnionCases |> List.item tag |> getUnionCaseName |> ofString
            let values = (ofInt tag) :: values
            Expression.call (consRef, values, ?loc = r), stmts @ stmts'
        | _ -> failwith $"transformValue: value {value} not supported!"

    let enumerator2iterator com ctx =
        let enumerator =
            Expression.call (get com ctx None (Expression.identifier "self") "GetEnumerator" false, [])

        [ Statement.return' (libCall com ctx None "util" "to_iterator" [ enumerator ]) ]

    let extractBaseExprFromBaseCall
        (com: IPythonCompiler)
        (ctx: Context)
        (baseType: Fable.DeclaredType option)
        baseCall
        =
        // printfn "extractBaseExprFromBaseCall: %A" (baseCall, baseType)
        match baseCall, baseType with
        | Some(Fable.Call(baseRef, info, _, _)), _ ->
            let baseExpr, stmts =
                match baseRef with
                | Fable.IdentExpr id -> com.GetIdentifierAsExpr(ctx, id.Name), []
                | _ -> transformAsExpr com ctx baseRef

            let expr, keywords, stmts' = transformCallArgs com ctx info

            Some(baseExpr, (expr, keywords, stmts @ stmts'))
        | Some(Fable.ObjectExpr([], Fable.Unit, None)), _ ->
            let range = baseCall |> Option.bind (fun x -> x.Range)

            let name =
                baseType
                |> Option.map (fun t -> t.Entity.FullName)
                |> Option.defaultValue "unknown type"

            $"Ignoring base call for %s{name}" |> addWarning com [] range

            None
        | Some(Fable.Value _), Some baseType ->
            // let baseEnt = com.GetEntity(baseType.Entity)
            // let entityName = FSharp2Fable.Helpers.getEntityDeclarationName com baseType.Entity
            // let entityType = FSharp2Fable.Util.getEntityType baseEnt
            // let baseRefId = makeTypedIdent entityType entityName
            // let baseExpr = (baseRefId |> typedIdent com ctx) :> Expression
            // Some (baseExpr, []) // default base constructor
            let range = baseCall |> Option.bind (fun x -> x.Range)

            $"Ignoring base call for %s{baseType.Entity.FullName}"
            |> addWarning com [] range

            None
        | Some _, _ ->
            let range = baseCall |> Option.bind (fun x -> x.Range)

            "Unexpected base call expression, please report" |> addError com [] range

            None
        | None, _ -> None

    let transformObjectExpr
        (com: IPythonCompiler)
        ctx
        (members: Fable.ObjectExprMember list)
        typ
        baseCall
        : Expression * Statement list
        =
        // printfn "transformObjectExpr: %A" typ

        // A generic class nested in another generic class cannot use same type variables. (PEP-484)
        let ctx = { ctx with TypeParamsScope = ctx.TypeParamsScope + 1 }

        let makeMethod prop hasSpread args body decorators =
            let args, body, returnType =
                getMemberArgsAndBody com ctx (Attached(isStatic = false)) hasSpread args body

            let name =
                let name =
                    match prop with
                    | "ToString" -> "__str__"
                    | _ -> prop

                com.GetIdentifier(ctx, Naming.toSnakeCase name)

            let self = Arg.arg "self"

            let args =
                match decorators with
                // Remove extra parameters from getters, i.e __unit=None
                | [ Expression.Name { Id = Identifier "property" } ] ->
                    { args with
                        Args = [ self ]
                        Defaults = []
                    }
                | _ -> { args with Args = self :: args.Args }

            Statement.functionDef (name, args, body, decorators, returns = returnType)

        let interfaces, stmts =
            match typ with
            | Fable.Any -> [], [] // Don't inherit from Any
            | _ ->
                let ta, stmts = typeAnnotation com ctx None typ
                [ ta ], stmts

        let members =
            members
            |> List.collect (fun memb ->
                let info = com.GetMember(memb.MemberRef)

                if not memb.IsMangled && (info.IsGetter || info.IsValue) then
                    let decorators = [ Expression.name "property" ]

                    [ makeMethod memb.Name false memb.Args memb.Body decorators ]
                elif not memb.IsMangled && info.IsSetter then
                    let decorators = [ Expression.name $"{memb.Name}.setter" ]

                    [ makeMethod memb.Name false memb.Args memb.Body decorators ]
                elif info.FullName = "System.Collections.Generic.IEnumerable.GetEnumerator" then
                    let method = makeMethod memb.Name info.HasSpread memb.Args memb.Body []

                    let iterator =
                        let body = enumerator2iterator com ctx
                        let name = com.GetIdentifier(ctx, "__iter__")
                        let args = Arguments.arguments [ Arg.arg "self" ]

                        Statement.functionDef (name = name, args = args, body = body)

                    [ method; iterator ]
                else
                    [ makeMethod memb.Name info.HasSpread memb.Args memb.Body [] ]
            )

        let _baseExpr, classMembers =
            baseCall
            |> extractBaseExprFromBaseCall com ctx None
            |> Option.map (fun (baseExpr, (baseArgs, _kw, _stmts)) ->
                let consBody = [ callSuperAsStatement baseArgs ]
                let args = Arguments.empty
                let classCons = makeClassConstructor args false consBody
                Some baseExpr, classCons @ members
            )
            |> Option.defaultValue (None, members)
            |> (fun (expr, memb) -> expr |> Option.toList, memb)

        let classBody =
            match classMembers with
            | [] -> [ Pass ]
            | _ -> classMembers

        let name = Helpers.getUniqueIdentifier "ObjectExpr"

        let stmt = Statement.classDef (name, body = classBody, bases = interfaces)

        Expression.call (Expression.name name), [ stmt ] @ stmts

    let transformCallArgs
        (com: IPythonCompiler)
        ctx
        (callInfo: Fable.CallInfo)
        : Expression list * Keyword list * Statement list
        =

        let args =
            FSharp2Fable.Util.dropUnitCallArg callInfo.Args callInfo.SignatureArgTypes

        let paramsInfo =
            callInfo.MemberRef |> Option.bind com.TryGetMember |> Option.map getParamsInfo

        let args, objArg, stmts =
            paramsInfo
            |> Option.map (splitNamedArgs args)
            |> function
                | None -> args, None, []
                | Some(args, []) -> args, None, []
                | Some(args, namedArgs) ->
                    let objArg, stmts =
                        namedArgs
                        |> List.choose (fun (p, v) ->
                            match p.Name, v with
                            | Some k, Fable.Value(Fable.NewOption(value, _, _), _) ->
                                value |> Option.map (fun v -> k, v)
                            | Some k, v -> Some(k, v)
                            | None, _ -> None
                        )
                        |> List.map (fun (k, v) -> k, com.TransformAsExpr(ctx, v))
                        |> List.map (fun (k, (v, stmts)) -> ((k, v), stmts))
                        |> List.unzip
                        |> (fun (kv, stmts) ->
                            kv |> List.map (fun (k, v) -> Keyword.keyword (Identifier k, v)), stmts |> List.collect id
                        )

                    args, Some objArg, stmts

        let hasSpread =
            paramsInfo |> Option.map (fun i -> i.HasSpread) |> Option.defaultValue false

        let args, stmts' =
            match args with
            | [] -> [], []
            | args when hasSpread ->
                match List.rev args with
                | [] -> [], []
                | Replacements.Util.ArrayOrListLiteral(spreadArgs, _) :: rest ->
                    let rest = List.rev rest |> List.map (fun e -> com.TransformAsExpr(ctx, e))

                    rest @ (List.map (fun e -> com.TransformAsExpr(ctx, e)) spreadArgs)
                    |> Helpers.unzipArgs
                | last :: rest ->
                    let rest, stmts =
                        List.rev rest
                        |> List.map (fun e -> com.TransformAsExpr(ctx, e))
                        |> Helpers.unzipArgs

                    let expr, stmts' = com.TransformAsExpr(ctx, last)
                    rest @ [ Expression.starred expr ], stmts @ stmts'
            | args -> List.map (fun e -> com.TransformAsExpr(ctx, e)) args |> Helpers.unzipArgs

        match objArg with
        | None -> args, [], stmts @ stmts'
        | Some objArg ->
            //let name = Expression.name(Helpers.getUniqueIdentifier "kw")
            //let kw = Statement.assign([ name], objArg)
            args, objArg, stmts @ stmts'

    let resolveExpr (ctx: Context) _t strategy pyExpr : Statement list =
        // printfn "resolveExpr: %A" (pyExpr, strategy)
        match strategy with
        | None
        | Some ReturnUnit -> exprAsStatement ctx pyExpr
        // TODO: Where to put these int wrappings? Add them also for function arguments?
        | Some ResourceManager
        | Some Return -> [ Statement.return' pyExpr ]
        | Some(Assign left) -> exprAsStatement ctx (assign None left pyExpr)
        | Some(Target left) -> exprAsStatement ctx (assign None (left |> Expression.identifier) pyExpr)

    let transformOperation com ctx range opKind tags : Expression * Statement list =
        match opKind with
        // | Fable.Unary (UnaryVoid, TransformExpr com ctx (expr, stmts)) -> Expression.none, stmts
        // | Fable.Unary (UnaryTypeof, TransformExpr com ctx (expr, stmts)) ->
        //     let func = Expression.name ("type")
        //     let args = [ expr ]
        //     Expression.call (func, args), stmts

        // Transform `~(~(a/b))` to `a // b`
        | Fable.Unary(UnaryOperator.UnaryNotBitwise,
                      Fable.Operation(
                          kind = Fable.Unary(UnaryOperator.UnaryNotBitwise,
                                             Fable.Operation(
                                                 kind = Fable.Binary(BinaryOperator.BinaryDivide,
                                                                     TransformExpr com ctx (left, stmts),
                                                                     TransformExpr com ctx (right, stmts')))))) ->
            Expression.binOp (left, FloorDiv, right), stmts @ stmts'
        | Fable.Unary(UnaryOperator.UnaryNotBitwise,
                      Fable.Operation(
                          kind = Fable.Unary(UnaryOperator.UnaryNotBitwise, TransformExpr com ctx (left, stmts)))) ->
            let name = Expression.name "int"
            Expression.call (name, [ left ]), stmts
        | Fable.Unary(op, TransformExpr com ctx (expr, stmts)) -> Expression.unaryOp (op, expr, ?loc = range), stmts

        // | Fable.Binary (BinaryInstanceOf, TransformExpr com ctx (left, stmts), TransformExpr com ctx (right, stmts')) ->
        //     let func = Expression.name ("isinstance")
        //     let args = [ left; right ]
        //     Expression.call (func, args), stmts' @ stmts

        | Fable.Binary(op, TransformExpr com ctx (left, stmts), TransformExpr com ctx (right, stmts')) ->
            let compare op =
                Expression.compare (left, [ op ], [ right ], ?loc = range), stmts @ stmts'

            let (|IsNone|_|) =
                function
                | Name { Id = Identifier "None" } -> Some()
                | _ -> None

            let strict =
                match tags with
                | Fable.Tags.Contains "strict" -> true
                | _ -> false

            match op, strict with
            | BinaryEqual, true ->
                match left, right with
                // Use == with literals
                | Constant _, _ -> compare Eq
                | _, Constant _ -> compare Eq
                | _ -> compare Is
            | BinaryEqual, false ->
                match left, right with
                // Use == with literals
                | Constant _, _ -> compare Eq
                | _, Constant _ -> compare Eq
                // Use `is` with None (except literals)
                | _, IsNone -> compare Is
                | IsNone, _ -> compare Is
                // Use == for the rest
                | _ -> compare Eq
            | BinaryUnequal, true ->
                match left, right with
                // Use == with literals
                | Constant _, _ -> compare NotEq
                | _, Constant _ -> compare NotEq
                | _ -> compare IsNot
            | BinaryUnequal, false ->
                match left, right with
                // Use != with literals
                | Constant _, _ -> compare NotEq
                | _, Constant _ -> compare NotEq
                // Use `is not` with None (except literals)
                | _, IsNone -> compare IsNot
                | IsNone, _ -> compare IsNot
                // Use != for the rest
                | _ -> compare NotEq
            | BinaryLess, _ -> compare Lt
            | BinaryLessOrEqual, _ -> compare LtE
            | BinaryGreater, _ -> compare Gt
            | BinaryGreaterOrEqual, _ -> compare GtE
            | _ -> Expression.binOp (left, op, right, ?loc = range), stmts @ stmts'

        | Fable.Logical(op, TransformExpr com ctx (left, stmts), TransformExpr com ctx (right, stmts')) ->
            Expression.boolOp (op, [ left; right ], ?loc = range), stmts @ stmts'

    let transformEmit (com: IPythonCompiler) ctx range (info: Fable.EmitInfo) =
        let macro = info.Macro
        let info = info.CallInfo

        let thisArg, stmts =
            info.ThisArg
            |> Option.map (fun e -> com.TransformAsExpr(ctx, e))
            |> Option.toList
            |> Helpers.unzipArgs

        let exprs, _, stmts' = transformCallArgs com ctx info

        if macro.StartsWith("functools", StringComparison.Ordinal) then
            com.GetImportExpr(ctx, "functools") |> ignore

        let args = exprs |> List.append thisArg
        emitExpression range macro args, stmts @ stmts'

    let transformCall (com: IPythonCompiler) ctx range callee (callInfo: Fable.CallInfo) : Expression * Statement list =
        // printfn "transformCall: %A" (callee, callInfo)
        let callee', stmts = com.TransformAsExpr(ctx, callee)

        let args, kw, stmts' = transformCallArgs com ctx callInfo

        match callee, callInfo.ThisArg with
        | Fable.Get(expr, Fable.FieldGet { Name = "Dispose" }, _, _), _ ->
            let expr, stmts'' = com.TransformAsExpr(ctx, expr)

            libCall com ctx range "util" "dispose" [ expr ], stmts @ stmts' @ stmts''
        | Fable.Get(expr, Fable.FieldGet { Name = "set" }, _, _), _ ->
            // printfn "Type: %A" expr.Type
            let right, stmts = com.TransformAsExpr(ctx, callInfo.Args.Head)

            let arg, stmts' = com.TransformAsExpr(ctx, callInfo.Args.Tail.Head)
            let value, stmts'' = com.TransformAsExpr(ctx, expr)

            Expression.none,
            Statement.assign ([ Expression.subscript (value, right) ], arg) :: stmts
            @ stmts'
            @ stmts''
        | Fable.Get(_, Fable.FieldGet { Name = "sort" }, _, _), _ -> callFunction range callee' [] kw, stmts @ stmts'

        | _, Some(TransformExpr com ctx (thisArg, stmts'')) ->
            callFunction range callee' (thisArg :: args) kw, stmts @ stmts' @ stmts''
        | _, None when List.contains "new" callInfo.Tags ->
            Expression.call (callee', args, kw, ?loc = range), stmts @ stmts'
        | _, None -> callFunction range callee' args kw, stmts @ stmts'

    let transformCurriedApply com ctx range (TransformExpr com ctx (applied, stmts)) args =
        ((applied, stmts), args)
        ||> List.fold (fun (applied, stmts) arg ->
            let args, stmts' =
                match arg with
                // TODO: If arg type is unit but it's an expression with potential
                // side-effects, we need to extract it and execute it before the call

                // TODO: discardUnitArg may still be needed in some cases
                // | Fable.Value(Fable.UnitConstant,_) -> [], []
                // | Fable.IdentExpr ident when ident.Type = Fable.Unit -> [], []
                | TransformExpr com ctx (arg, stmts') -> [ arg ], stmts'

            callFunction range applied args [], stmts @ stmts'
        )

    let transformCallAsStatements com ctx range t returnStrategy callee callInfo =
        let argsLen (i: Fable.CallInfo) =
            List.length i.Args
            + (if Option.isSome i.ThisArg then
                   1
               else
                   0)
        // Warn when there's a recursive call that couldn't be optimized?
        match returnStrategy, ctx.TailCallOpportunity with
        | Some(Return | ReturnUnit), Some tc when tc.IsRecursiveRef(callee) && argsLen callInfo = List.length tc.Args ->
            let args =
                match callInfo.ThisArg with
                | Some thisArg -> thisArg :: callInfo.Args
                | None -> callInfo.Args

            optimizeTailCall com ctx range tc args
        | _ ->
            let expr, stmts = transformCall com ctx range callee callInfo
            stmts @ (expr |> resolveExpr ctx t returnStrategy)

    let transformCurriedApplyAsStatements com ctx range t returnStrategy callee args =
        // Warn when there's a recursive call that couldn't be optimized?
        match returnStrategy, ctx.TailCallOpportunity with
        | Some(Return | ReturnUnit), Some tc when tc.IsRecursiveRef(callee) && List.sameLength args tc.Args ->
            optimizeTailCall com ctx range tc args
        | _ ->
            let expr, stmts = transformCurriedApply com ctx range callee args

            stmts @ (expr |> resolveExpr ctx t returnStrategy)

    let getNonLocals ctx (body: Statement list) =
        let body, nonLocals =
            body
            |> List.partition (
                function
                | Statement.NonLocal _
                | Statement.Global _ -> false
                | _ -> true
            )

        let nonLocal =
            nonLocals
            |> List.collect (
                function
                | Statement.NonLocal nl -> nl.Names
                | Statement.Global gl -> gl.Names
                | _ -> []
            )
            |> List.distinct
            |> (fun names ->
                match ctx.BoundVars.Inceptions with
                | 1 -> Statement.global' names
                | _ -> Statement.nonLocal names
            )

        [ nonLocal ], body

    let transformBody (_com: IPythonCompiler) ctx _ret (body: Statement list) : Statement list =
        match body with
        | [] -> [ Pass ]
        | _ ->
            let nonLocals, body = getNonLocals ctx body
            nonLocals @ body

    // When expecting a block, it's usually not necessary to wrap it
    // in a lambda to isolate its variable context
    let transformBlock (com: IPythonCompiler) ctx ret (expr: Fable.Expr) : Statement list =
        let block =
            com.TransformAsStatements(ctx, ret, expr)
            |> List.choose Helpers.isProductiveStatement

        match block with
        | [] -> [ Pass ]
        | _ -> block |> transformBody com ctx ret

    let transformTryCatch
        com
        (ctx: Context)
        r
        returnStrategy
        (body, catch: option<Fable.Ident * Fable.Expr>, finalizer)
        =
        // try .. catch statements cannot be tail call optimized
        let ctx = { ctx with TailCallOpportunity = None }

        let handlers =
            catch
            |> Option.map (fun (param, body) ->
                let body = transformBlock com ctx returnStrategy body
                let exn = Expression.identifier "Exception" |> Some
                let identifier = ident com ctx param

                [ ExceptHandler.exceptHandler (``type`` = exn, name = identifier, body = body) ]
            )

        let finalizer, stmts =
            match finalizer with
            | Some finalizer ->
                finalizer
                |> transformBlock com ctx None
                |> List.partition (
                    function
                    | Statement.NonLocal _
                    | Statement.Global _ -> false
                    | _ -> true
                )
            | None -> [], []

        stmts
        @ [
            Statement.try' (
                transformBlock com ctx returnStrategy body,
                ?handlers = handlers,
                finalBody = finalizer,
                ?loc = r
            )
        ]

    let rec transformIfStatement (com: IPythonCompiler) ctx r ret guardExpr thenStmnt elseStmnt =
        // printfn "transformIfStatement"
        let expr, stmts = com.TransformAsExpr(ctx, guardExpr)

        match expr with
        | Constant(value = BoolLiteral value) -> stmts @ com.TransformAsStatements(ctx, ret, thenStmnt)
        | guardExpr ->
            let thenStmnt, stmts' =
                transformBlock com ctx ret thenStmnt
                |> List.partition (
                    function
                    | Statement.NonLocal _
                    | Statement.Global _ -> false
                    | _ -> true
                )

            let ifStatement, stmts'' =
                let block, stmts =
                    transformBlock com ctx ret elseStmnt
                    |> List.partition (
                        function
                        | Statement.NonLocal _
                        | Statement.Global _ -> false
                        | _ -> true
                    )

                match block with
                | [] -> Statement.if' (guardExpr, thenStmnt, ?loc = r), stmts
                | [ elseStmnt ] -> Statement.if' (guardExpr, thenStmnt, [ elseStmnt ], ?loc = r), stmts
                | statements -> Statement.if' (guardExpr, thenStmnt, statements, ?loc = r), stmts

            stmts @ stmts' @ stmts'' @ [ ifStatement ]

    let transformGet (com: IPythonCompiler) ctx range typ (fableExpr: Fable.Expr) kind =
        // printfn "transformGet: %A" kind
        // printfn "transformGet: %A" (fableExpr.Type)

        match kind with
        | Fable.ExprGet(TransformExpr com ctx (prop, stmts)) ->
            let expr, stmts' = com.TransformAsExpr(ctx, fableExpr)
            let expr, stmts'' = getExpr com ctx range expr prop
            expr, stmts @ stmts' @ stmts''

        | Fable.FieldGet i ->
            // printfn "Fable.FieldGet: %A" (i.Name, fableExpr.Type)
            let fieldName = i.Name |> Naming.toSnakeCase // |> Helpers.clean

            let fableExpr =
                match fableExpr with
                // If we're accessing a virtual member with default implementation (see #701)
                // from base class, we can use `super` in JS so we don't need the bound this arg
                | Fable.Value(Fable.BaseValue(_, t), r) -> Fable.Value(Fable.BaseValue(None, t), r)
                | _ -> fableExpr

            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)

            let subscript =
                match fableExpr.Type with
                | Fable.AnonymousRecordType _ -> true
                | Fable.GenericParam(_, _, [ Fable.Constraint.HasMember(_, false) ]) -> true
                | _ -> false
            // printfn "Fable.FieldGet: %A" (fieldName, fableExpr.Type)
            get com ctx range expr fieldName subscript, stmts

        | Fable.ListHead ->
            // get range (com.TransformAsExpr(ctx, fableExpr)) "head"
            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)
            libCall com ctx range "list" "head" [ expr ], stmts

        | Fable.ListTail ->
            // get range (com.TransformAsExpr(ctx, fableExpr)) "tail"
            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)
            libCall com ctx range "list" "tail" [ expr ], stmts

        | Fable.TupleIndex index ->
            match fableExpr with
            // TODO: Check the erased expressions don't have side effects?
            | Fable.Value(Fable.NewTuple(exprs, _), _) -> com.TransformAsExpr(ctx, List.item index exprs)
            | TransformExpr com ctx (expr, stmts) ->
                let expr, stmts' = getExpr com ctx range expr (ofInt index)
                expr, stmts @ stmts'

        | Fable.OptionValue ->
            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)

            if mustWrapOption typ || com.Options.Language = TypeScript then
                libCall com ctx None "option" "value" [ expr ], stmts
            else
                expr, stmts

        | Fable.UnionTag ->
            let expr, stmts = getUnionExprTag com ctx range fableExpr
            expr, stmts

        | Fable.UnionField i ->
            let expr, stmts = com.TransformAsExpr(ctx, fableExpr)

            let expr, stmts' = getExpr com ctx None expr (Expression.stringConstant "fields")

            let expr, stmts'' = getExpr com ctx range expr (ofInt i.FieldIndex)

            expr, stmts @ stmts' @ stmts''

    let transformSet (com: IPythonCompiler) ctx range fableExpr typ (value: Fable.Expr) kind =
        // printfn "transformSet: %A" (fableExpr, value)
        let expr, stmts = com.TransformAsExpr(ctx, fableExpr)

        let value, stmts' =
            let value, st = com.TransformAsExpr(ctx, value)
            value |> wrapIntExpression typ, st

        let ret, stmts'' =
            match kind with
            | Fable.ValueSet -> expr, []
            | Fable.ExprSet(TransformExpr com ctx (e, stmts'')) ->
                let expr, stmts''' = getExpr com ctx None expr e
                expr, stmts'' @ stmts'''
            | Fable.FieldSet fieldName ->
                let fieldName = fieldName |> Naming.toSnakeCase |> Helpers.clean
                get com ctx None expr fieldName false, []

        assign range ret value, stmts @ stmts' @ stmts''

    let transformBindingExprBody (com: IPythonCompiler) (ctx: Context) (var: Fable.Ident) (value: Fable.Expr) =
        match value with
        | Function(args, body) ->
            let name = Some var.Name

            transformFunctionWithAnnotations com ctx name args body
            |||> makeArrowFunctionExpression com ctx name
        | _ ->
            let expr, stmt = com.TransformAsExpr(ctx, value)
            expr |> wrapIntExpression value.Type, stmt

    let transformBindingAsExpr (com: IPythonCompiler) ctx (var: Fable.Ident) (value: Fable.Expr) =
        //printfn "transformBindingAsExpr: %A" (var, value)
        let expr, stmts = transformBindingExprBody com ctx var value
        expr |> assign None (identAsExpr com ctx var), stmts

    let transformBindingAsStatements (com: IPythonCompiler) ctx (var: Fable.Ident) (value: Fable.Expr) =
        // printfn "transformBindingAsStatements: %A" (var, value)
        if isPyStatement ctx false value then
            let varName, varExpr = Expression.name var.Name, identAsExpr com ctx var

            ctx.BoundVars.Bind(var.Name)
            let ta, stmts = typeAnnotation com ctx None var.Type
            let decl = Statement.assign (varName, ta)

            let body = com.TransformAsStatements(ctx, Some(Assign varExpr), value)

            stmts @ [ decl ] @ body
        else
            let value, stmts = transformBindingExprBody com ctx var value
            let varName = com.GetIdentifierAsExpr(ctx, Naming.toSnakeCase var.Name)
            let ta, stmts' = typeAnnotation com ctx None var.Type
            let decl = varDeclaration ctx varName (Some ta) value
            stmts @ stmts' @ decl

    let transformTest (com: IPythonCompiler) ctx range kind expr : Expression * Statement list =
        match kind with
        | Fable.TypeTest t -> transformTypeTest com ctx range expr t

        | Fable.OptionTest nonEmpty ->
            let op =
                if nonEmpty then
                    IsNot
                else
                    Is

            let expr, stmts = com.TransformAsExpr(ctx, expr)

            Expression.compare (expr, [ op ], [ Expression.none ], ?loc = range), stmts

        | Fable.ListTest nonEmpty ->
            let expr, stmts = com.TransformAsExpr(ctx, expr)
            let expr = libCall com ctx range "list" "isEmpty" [ expr ]

            if nonEmpty then
                Expression.unaryOp (UnaryNot, expr, ?loc = range), stmts
            else
                expr, stmts

        | Fable.UnionCaseTest tag ->
            let expected = ofInt tag
            let actual, stmts = getUnionExprTag com ctx None expr

            Expression.compare (actual, [ Eq ], [ expected ], ?loc = range), stmts

    let transformSwitch
        (com: IPythonCompiler)
        ctx
        _useBlocks
        returnStrategy
        evalExpr
        cases
        defaultCase
        : Statement list
        =
        let cases =
            cases
            |> List.collect (fun (guards, expr) ->
                // Remove empty branches
                match returnStrategy, expr, guards with
                | None, Fable.Value(Fable.UnitConstant, _), _
                | _, _, [] -> []
                | _, _, guards ->
                    let guards, lastGuard = List.splitLast guards

                    let guards =
                        guards
                        |> List.map (fun e ->
                            let expr, stmts = com.TransformAsExpr(ctx, e)
                            (stmts, Some expr)
                        )

                    let caseBody = com.TransformAsStatements(ctx, returnStrategy, expr)

                    let caseBody =
                        match returnStrategy with
                        | Some Return -> caseBody
                        | _ -> List.append caseBody [ Statement.break' () ]

                    let expr, stmts = com.TransformAsExpr(ctx, lastGuard)
                    guards @ [ (stmts @ caseBody, Some expr) ]
            )

        let cases =
            match defaultCase with
            | Some expr ->
                let defaultCaseBody = com.TransformAsStatements(ctx, returnStrategy, expr)

                cases @ [ (defaultCaseBody, None) ]
            | None -> cases

        let value, stmts = com.TransformAsExpr(ctx, evalExpr)

        let rec ifThenElse
            (fallThrough: Expression option)
            (cases: (Statement list * Expression option) list)
            : Statement list
            =
            match cases with
            | [] -> []
            | (body, test) :: cases ->
                match test with
                | None -> body
                | Some test ->
                    let expr = Expression.compare (left = value, ops = [ Eq ], comparators = [ test ])

                    let test =
                        match fallThrough with
                        | Some ft -> Expression.boolOp (op = Or, values = [ ft; expr ])
                        | _ -> expr

                    // Check for fallthrough
                    if body.IsEmpty then
                        ifThenElse (Some test) cases
                    else
                        // Remove any break statements from body
                        let body =
                            body
                            |> List.filter (
                                function
                                | Statement.Break -> false
                                | _ -> true
                            )
                            |> function
                                // Make sure we don't have an empty body
                                | [] -> [ Statement.Pass ]
                                | body -> body

                        let nonLocals, body = getNonLocals ctx body

                        let nonLocals, orElse =
                            ifThenElse None cases |> List.append nonLocals |> getNonLocals ctx

                        nonLocals @ [ Statement.if' (test = test, body = body, orelse = orElse) ]

        let result = cases |> ifThenElse None

        match result with
        | [] -> []
        | ifStmt -> stmts @ ifStmt

    let matchTargetIdentAndValues idents values =
        if List.isEmpty idents then
            []
        elif List.sameLength idents values then
            List.zip idents values
        else
            failwith "Target idents/values lengths differ"

    let getDecisionTargetAndBoundValues (com: IPythonCompiler) (ctx: Context) targetIndex boundValues =
        let idents, target = getDecisionTarget ctx targetIndex
        let identsAndValues = matchTargetIdentAndValues idents boundValues

        if not com.Options.DebugMode then
            let bindings, replacements =
                (([], Map.empty), identsAndValues)
                ||> List.fold (fun (bindings, replacements) (ident, expr) ->
                    if canHaveSideEffects expr then
                        (ident, expr) :: bindings, replacements
                    else
                        bindings, Map.add ident.Name expr replacements
                )

            let target = FableTransforms.replaceValues replacements target
            target, List.rev bindings
        else
            target, identsAndValues

    let transformDecisionTreeSuccessAsExpr (com: IPythonCompiler) (ctx: Context) targetIndex boundValues =
        let target, bindings =
            getDecisionTargetAndBoundValues com ctx targetIndex boundValues

        match bindings with
        | [] -> com.TransformAsExpr(ctx, target)
        | bindings ->
            let target =
                List.rev bindings |> List.fold (fun e (i, v) -> Fable.Let(i, v, e)) target

            com.TransformAsExpr(ctx, target)

    let exprAsStatement (ctx: Context) (expr: Expression) : Statement list =
        // printfn "exprAsStatement: %A" expr
        match expr with
        // A single None will be removed (i.e transformCall may return None)
        | Name { Id = Identifier "None" } -> []
        | NamedExpr({
                        Target = target
                        Value = value
                        Loc = _
                    }) ->
            let nonLocals =
                match target with
                | Expression.Name { Id = id } -> ctx.BoundVars.NonLocals([ id ]) |> Statement.nonLocal |> List.singleton
                | _ -> []

            // printfn "Nonlocals: %A" nonLocals
            nonLocals @ [ Statement.assign ([ target ], value) ]
        | _ -> [ Statement.expr expr ]

    let transformDecisionTreeSuccessAsStatements
        (com: IPythonCompiler)
        (ctx: Context)
        returnStrategy
        targetIndex
        boundValues
        : Statement list
        =
        match returnStrategy with
        | Some(Target targetId) as _target ->
            let idents, _ = getDecisionTarget ctx targetIndex

            let assignments =
                matchTargetIdentAndValues idents boundValues
                |> List.collect (fun (id, TransformExpr com ctx (value, stmts)) ->
                    let stmts' = assign None (identAsExpr com ctx id) value |> exprAsStatement ctx

                    stmts @ stmts'
                )

            let targetAssignment =
                assign None (targetId |> Expression.name) (ofInt targetIndex)
                |> exprAsStatement ctx

            targetAssignment @ assignments
        | ret ->
            let target, bindings =
                getDecisionTargetAndBoundValues com ctx targetIndex boundValues

            let bindings =
                bindings
                |> Seq.collect (fun (i, v) -> transformBindingAsStatements com ctx i v)
                |> Seq.toList

            bindings @ com.TransformAsStatements(ctx, ret, target)

    let transformDecisionTreeAsSwitch expr =
        let (|Equals|_|) =
            function
            | Fable.Operation(Fable.Binary(BinaryEqual, expr, right), _, _, _) ->
                match expr with
                | Fable.Value((Fable.CharConstant _ | Fable.StringConstant _ | Fable.NumberConstant _), _) ->
                    Some(expr, right)
                | _ -> None
            | Fable.Test(expr, Fable.UnionCaseTest tag, _) ->
                let evalExpr =
                    Fable.Get(expr, Fable.UnionTag, Fable.Number(Int32, Fable.NumberInfo.Empty), None)

                let right = makeIntConst tag
                Some(evalExpr, right)
            | _ -> None

        let sameEvalExprs evalExpr1 evalExpr2 =
            match evalExpr1, evalExpr2 with
            | Fable.IdentExpr i1, Fable.IdentExpr i2
            | Fable.Get(Fable.IdentExpr i1, Fable.UnionTag, _, _), Fable.Get(Fable.IdentExpr i2, Fable.UnionTag, _, _) ->
                i1.Name = i2.Name
            | _ -> false

        let rec checkInner cases evalExpr =
            function
            | Fable.IfThenElse(Equals(evalExpr2, caseExpr),
                               Fable.DecisionTreeSuccess(targetIndex, boundValues, _),
                               treeExpr,
                               _) when sameEvalExprs evalExpr evalExpr2 ->
                match treeExpr with
                | Fable.DecisionTreeSuccess(defaultTargetIndex, defaultBoundValues, _) ->
                    let cases = (caseExpr, targetIndex, boundValues) :: cases |> List.rev

                    Some(evalExpr, cases, (defaultTargetIndex, defaultBoundValues))
                | treeExpr -> checkInner ((caseExpr, targetIndex, boundValues) :: cases) evalExpr treeExpr
            | _ -> None

        match expr with
        | Fable.IfThenElse(Equals(evalExpr, caseExpr),
                           Fable.DecisionTreeSuccess(targetIndex, boundValues, _),
                           treeExpr,
                           _) ->
            match checkInner [ caseExpr, targetIndex, boundValues ] evalExpr treeExpr with
            | Some(evalExpr, cases, defaultCase) -> Some(evalExpr, cases, defaultCase)
            | None -> None
        | _ -> None

    let transformDecisionTreeAsExpr (com: IPythonCompiler) (ctx: Context) targets expr : Expression * Statement list =
        // TODO: Check if some targets are referenced multiple times
        let ctx = { ctx with DecisionTargets = targets }
        com.TransformAsExpr(ctx, expr)

    let groupSwitchCases t (cases: (Fable.Expr * int * Fable.Expr list) list) (defaultIndex, defaultBoundValues) =
        cases
        |> List.groupBy (fun (_, idx, boundValues) ->
            // Try to group cases with some target index and empty bound values
            // If bound values are non-empty use also a non-empty Guid to prevent grouping
            if List.isEmpty boundValues then
                idx, Guid.Empty
            else
                idx, Guid.NewGuid()
        )
        |> List.map (fun ((idx, _), cases) ->
            let caseExprs = cases |> List.map Tuple3.item1
            // If there are multiple cases, it means boundValues are empty
            // (see `groupBy` above), so it doesn't mind which one we take as reference
            let boundValues = cases |> List.head |> Tuple3.item3
            caseExprs, Fable.DecisionTreeSuccess(idx, boundValues, t)
        )
        |> function
            | [] -> []
            // Check if the last case can also be grouped with the default branch, see #2357
            | cases when List.isEmpty defaultBoundValues ->
                match List.splitLast cases with
                | cases, (_, Fable.DecisionTreeSuccess(idx, [], _)) when idx = defaultIndex -> cases
                | _ -> cases
            | cases -> cases

    let getTargetsWithMultipleReferences expr =
        let rec findSuccess (targetRefs: Map<int, int>) =
            function
            | [] -> targetRefs
            | expr :: exprs ->
                match expr with
                // We shouldn't actually see this, but shortcircuit just in case
                | Fable.DecisionTree _ -> findSuccess targetRefs exprs
                | Fable.DecisionTreeSuccess(idx, _, _) ->
                    let count = Map.tryFind idx targetRefs |> Option.defaultValue 0

                    let targetRefs = Map.add idx (count + 1) targetRefs
                    findSuccess targetRefs exprs
                | expr ->
                    let exprs2 = getSubExpressions expr
                    findSuccess targetRefs (exprs @ exprs2)

        findSuccess Map.empty [ expr ]
        |> Seq.choose (fun kv ->
            if kv.Value > 1 then
                Some kv.Key
            else
                None
        )
        |> Seq.toList

    /// When several branches share target create first a switch to get the target index and bind value
    /// and another to execute the actual target
    let transformDecisionTreeWithTwoSwitches
        (com: IPythonCompiler)
        ctx
        returnStrategy
        (targets: (Fable.Ident list * Fable.Expr) list)
        treeExpr
        =
        // Declare target and bound idents
        let targetId =
            getUniqueNameInDeclarationScope ctx "pattern_matching_result" |> makeIdent

        let multiVarDecl =
            let boundIdents =
                targets
                |> List.collect (fun (idents, _) -> idents)
                |> List.map (fun id -> ident com ctx id, None)

            multiVarDeclaration ctx ((ident com ctx targetId, None) :: boundIdents)
        // Transform targets as switch
        let switch2 =
            // TODO: Declare the last case as the default case?
            let cases = targets |> List.mapi (fun i (_, target) -> [ makeIntConst i ], target)

            transformSwitch com ctx true returnStrategy (targetId |> Fable.IdentExpr) cases None

        // Transform decision tree
        let targetAssign = Target(ident com ctx targetId)
        let ctx = { ctx with DecisionTargets = targets }

        match transformDecisionTreeAsSwitch treeExpr with
        | Some(evalExpr, cases, (defaultIndex, defaultBoundValues)) ->
            let cases =
                groupSwitchCases (Fable.Number(Int32, Fable.NumberInfo.Empty)) cases (defaultIndex, defaultBoundValues)

            let defaultCase =
                Fable.DecisionTreeSuccess(defaultIndex, defaultBoundValues, Fable.Number(Int32, Fable.NumberInfo.Empty))

            let switch1 =
                transformSwitch com ctx false (Some targetAssign) evalExpr cases (Some defaultCase)

            multiVarDecl @ switch1 @ switch2
        | None ->
            let decisionTree = com.TransformAsStatements(ctx, Some targetAssign, treeExpr)

            multiVarDecl @ decisionTree @ switch2

    let transformDecisionTreeAsStatements
        (com: IPythonCompiler)
        (ctx: Context)
        returnStrategy
        (targets: (Fable.Ident list * Fable.Expr) list)
        (treeExpr: Fable.Expr)
        : Statement list
        =
        // If some targets are referenced multiple times, hoist bound idents,
        // resolve the decision index and compile the targets as a switch
        let targetsWithMultiRefs =
            if com.Options.Language = TypeScript then
                [] // no hoisting when compiled with types
            else
                getTargetsWithMultipleReferences treeExpr

        match targetsWithMultiRefs with
        | [] ->
            let ctx = { ctx with DecisionTargets = targets }

            match transformDecisionTreeAsSwitch treeExpr with
            | Some(evalExpr, cases, (defaultIndex, defaultBoundValues)) ->
                let t = treeExpr.Type

                let cases =
                    cases
                    |> List.map (fun (caseExpr, targetIndex, boundValues) ->
                        [ caseExpr ], Fable.DecisionTreeSuccess(targetIndex, boundValues, t)
                    )

                let defaultCase = Fable.DecisionTreeSuccess(defaultIndex, defaultBoundValues, t)

                transformSwitch com ctx true returnStrategy evalExpr cases (Some defaultCase)
            | None -> com.TransformAsStatements(ctx, returnStrategy, treeExpr)
        | targetsWithMultiRefs ->
            // If the bound idents are not referenced in the target, remove them
            let targets =
                targets
                |> List.map (fun (idents, expr) ->
                    idents
                    |> List.exists (fun i -> isIdentUsed i.Name expr)
                    |> function
                        | true -> idents, expr
                        | false -> [], expr
                )

            let hasAnyTargetWithMultiRefsBoundValues =
                targetsWithMultiRefs
                |> List.exists (fun idx -> targets[idx] |> fst |> List.isEmpty |> not)

            if not hasAnyTargetWithMultiRefsBoundValues then
                match transformDecisionTreeAsSwitch treeExpr with
                | Some(evalExpr, cases, (defaultIndex, defaultBoundValues)) ->
                    let t = treeExpr.Type

                    let cases = groupSwitchCases t cases (defaultIndex, defaultBoundValues)

                    let ctx = { ctx with DecisionTargets = targets }

                    let defaultCase = Fable.DecisionTreeSuccess(defaultIndex, defaultBoundValues, t)

                    transformSwitch com ctx true returnStrategy evalExpr cases (Some defaultCase)
                | None -> transformDecisionTreeWithTwoSwitches com ctx returnStrategy targets treeExpr
            else
                transformDecisionTreeWithTwoSwitches com ctx returnStrategy targets treeExpr

    let transformSequenceExpr (com: IPythonCompiler) ctx (exprs: Fable.Expr list) : Expression * Statement list =
        // printfn "transformSequenceExpr"
        let ctx = { ctx with BoundVars = ctx.BoundVars.EnterScope() }

        let body =
            exprs
            |> List.collecti (fun i e ->
                let expr, stmts = com.TransformAsExpr(ctx, e)
                // Return the last expression
                if i = exprs.Length - 1 then
                    stmts @ [ Statement.return' expr ]
                else
                    stmts @ exprAsStatement ctx expr
            )
            |> transformBody com ctx None

        let name = Helpers.getUniqueIdentifier "_expr"

        let func =
            Statement.functionDef (name = name, args = Arguments.arguments [], body = body)

        let name = Expression.name name
        Expression.call name, [ func ]

    let transformSequenceExpr'
        (_com: IPythonCompiler)
        ctx
        (exprs: Expression list)
        (stmts: Statement list)
        : Expression * Statement list
        =
        // printfn "transformSequenceExpr2', exprs: %A" exprs.Length
        // printfn "ctx: %A" ctx.BoundVars
        let ctx = { ctx with BoundVars = ctx.BoundVars.EnterScope() }

        let body =
            exprs
            |> List.collecti (fun i expr ->
                // Return the last expression
                if i = exprs.Length - 1 then
                    stmts @ [ Statement.return' expr ]
                else
                    exprAsStatement ctx expr
            )

        let name = Helpers.getUniqueIdentifier "_expr"

        let func =
            Statement.functionDef (name = name, args = Arguments.arguments [], body = body)

        let name = Expression.name name
        Expression.call name, [ func ]

    let rec transformAsExpr (com: IPythonCompiler) ctx (expr: Fable.Expr) : Expression * Statement list =
        // printfn "transformAsExpr: %A" expr
        match expr with
        | Fable.Unresolved(_, _, r) -> addErrorAndReturnNull com r "Unexpected unresolved expression", []

        | Fable.TypeCast(e, t) -> transformCast com ctx t e

        | Fable.Value(kind, r) -> transformValue com ctx r kind

        | Fable.IdentExpr id -> identAsExpr com ctx id, []

        | Fable.Import({
                           Selector = selector
                           Path = path
                       },
                       _,
                       r) ->
            // printfn "Fable.Import: %A" (selector, path)
            transformImport com ctx r selector path, []

        | Fable.Test(expr, kind, range) -> transformTest com ctx range kind expr

        | Fable.Lambda(arg, body, name) ->
            transformFunctionWithAnnotations com ctx name [ arg ] body
            |||> makeArrowFunctionExpression com ctx name

        | Fable.Delegate(args, body, name, _) ->
            transformFunctionWithAnnotations com ctx name args body
            |||> makeArrowFunctionExpression com ctx name

        | Fable.ObjectExpr([], _typ, None) -> Expression.dict (), []
        | Fable.ObjectExpr(members, typ, baseCall) ->
            // printfn "members: %A" (members, typ)
            transformObjectExpr com ctx members typ baseCall

        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "has" }, _, _), info, _, _range) ->
            let left, stmts = com.TransformAsExpr(ctx, info.Args.Head)
            let value, stmts' = com.TransformAsExpr(ctx, expr)

            Expression.compare (left, [ ComparisonOperator.In ], [ value ]), stmts @ stmts'

        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "slice" }, _, _), info, _, _range) ->
            transformAsSlice com ctx expr info

        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "to_array" }, _, _), info, _, _range) ->
            transformAsArray com ctx expr info

        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "Equals" }, _, _), { Args = [ arg ] }, _, _range) ->
            let right, stmts = com.TransformAsExpr(ctx, arg)
            let left, stmts' = com.TransformAsExpr(ctx, expr)
            Expression.compare (left, [ Eq ], [ right ]), stmts @ stmts'

        | Fable.Call(callee, info, _, range) -> transformCall com ctx range callee info

        | Fable.CurriedApply(callee, args, _, range) -> transformCurriedApply com ctx range callee args

        | Fable.Operation(kind, tags, _, range) -> transformOperation com ctx range kind tags

        | Fable.Get(expr, kind, typ, range) -> transformGet com ctx range typ expr kind

        | Fable.IfThenElse(TransformExpr com ctx (guardExpr, stmts),
                           TransformExpr com ctx (thenExpr, stmts'),
                           TransformExpr com ctx (elseExpr, stmts''),
                           _r) -> Expression.ifExp (guardExpr, thenExpr, elseExpr), stmts @ stmts' @ stmts''

        | Fable.DecisionTree(expr, targets) -> transformDecisionTreeAsExpr com ctx targets expr

        | Fable.DecisionTreeSuccess(idx, boundValues, _) -> transformDecisionTreeSuccessAsExpr com ctx idx boundValues

        | Fable.Set(expr, kind, typ, value, range) ->
            let expr', stmts = transformSet com ctx range expr typ value kind
            // printfn "transformAsExpr: Fable.Set: %A" expr
            match expr' with
            | Expression.NamedExpr {
                                       Target = target
                                       Value = _
                                       Loc = _
                                   } ->
                let nonLocals =
                    match target with
                    | Expression.Name { Id = id } -> [ ctx.BoundVars.NonLocals([ id ]) |> Statement.nonLocal ]
                    | _ -> []

                expr', nonLocals @ stmts
            | _ -> expr', stmts

        | Fable.Let(_ident, _value, _body) ->
            // printfn "Fable.Let: %A" (ident, value, body)
            iife com ctx expr

        | Fable.LetRec(bindings, body) ->
            if ctx.HoistVars(List.map fst bindings) then
                let values, stmts =
                    bindings
                    |> List.map (fun (id, value) -> transformBindingAsExpr com ctx id value)
                    |> List.unzip
                    |> (fun (e, s) -> (e, List.collect id s))

                let expr, stmts' = com.TransformAsExpr(ctx, body)

                let expr, stmts'' = transformSequenceExpr' com ctx (values @ [ expr ]) []

                expr, stmts @ stmts' @ stmts''
            else
                iife com ctx expr

        | Fable.Sequential exprs -> transformSequenceExpr com ctx exprs

        | Fable.Emit(info, _, range) ->
            if info.IsStatement then
                iife com ctx expr
            else
                transformEmit com ctx range info

        // These cannot appear in expression position in Python, must be wrapped in a lambda
        | Fable.WhileLoop _
        | Fable.ForLoop _
        | Fable.TryCatch _ -> iife com ctx expr
        | Fable.Extended(instruction, _) ->
            match instruction with
            | Fable.Curry(e, arity) -> transformCurry com ctx e arity
            | Fable.Throw _
            | Fable.Debugger -> iife com ctx expr

    let transformAsSlice (com: IPythonCompiler) ctx expr (info: Fable.CallInfo) : Expression * Statement list =
        let left, stmts = com.TransformAsExpr(ctx, expr)

        let args, stmts' =
            info.Args
            |> List.map (fun arg -> com.TransformAsExpr(ctx, arg))
            |> List.unzip
            |> (fun (e, s) -> (e, List.collect id s))

        let slice =
            match args with
            | [] -> Expression.slice ()
            | [ lower ] -> Expression.slice (lower = lower)
            | [ Expression.Name { Id = Identifier "None" }; upper ] -> Expression.slice (upper = upper)
            | [ lower; upper ] -> Expression.slice (lower = lower, upper = upper)
            | _ -> failwith $"Array slice with {args.Length} not supported"

        Expression.subscript (left, slice), stmts @ stmts'

    let transformAsArray (com: IPythonCompiler) ctx expr (info: Fable.CallInfo) : Expression * Statement list =
        let value, stmts = com.TransformAsExpr(ctx, expr)

        match expr.Type with
        | Fable.Type.Array(typ, Fable.ArrayKind.ResizeArray) ->
            let letter =
                match typ with
                | Fable.Type.Number(UInt8, _) -> Some "B"
                | Fable.Type.Number(Int8, _) -> Some "b"
                | Fable.Type.Number(Int16, _) -> Some "h"
                | Fable.Type.Number(UInt16, _) -> Some "H"
                | Fable.Type.Number(Int32, _) -> Some "l"
                | Fable.Type.Number(UInt32, _) -> Some "L"
                | Fable.Type.Number(Int64, _) -> Some "q"
                | Fable.Type.Number(UInt64, _) -> Some "Q"
                | Fable.Type.Number(Float32, _) -> Some "f"
                | Fable.Type.Number(Float64, _) -> Some "d"
                | _ -> None

            match letter with
            | Some "B" ->
                let bytearray = Expression.name "bytearray"
                Expression.call (bytearray, [ value ]), stmts
            | Some l ->
                let array = com.GetImportExpr(ctx, "array", "array")

                Expression.call (array, Expression.stringConstant l :: [ value ]), stmts
            | _ -> transformAsSlice com ctx expr info
        | _ -> transformAsSlice com ctx expr info

    let rec transformAsStatements (com: IPythonCompiler) ctx returnStrategy (expr: Fable.Expr) : Statement list =
        // printfn "transformAsStatements: %A" expr
        match expr with
        | Fable.Unresolved(_, _, r) ->
            addError com [] r "Unexpected unresolved expression"
            []

        | Fable.Extended(kind, _r) ->
            match kind with
            | Fable.Curry(e, arity) ->
                let expr, stmts = transformCurry com ctx e arity

                stmts @ (expr |> resolveExpr ctx e.Type returnStrategy)
            | Fable.Throw(expr, _) ->
                match expr with
                | None -> failwith "TODO: rethrow"
                | Some(TransformExpr com ctx (e, stmts)) -> stmts @ [ Statement.raise e ]
            | Fable.Debugger ->
                [
                    Statement.assert' (Expression.boolOp (op = Or, values = [ Expression.boolConstant true ]))
                ]

        | Fable.TypeCast(e, t) ->
            let expr, stmts = transformCast com ctx t e
            stmts @ (expr |> resolveExpr ctx t returnStrategy)

        | Fable.Value(kind, r) ->
            let expr, stmts = transformValue com ctx r kind

            stmts @ (expr |> resolveExpr ctx kind.Type returnStrategy)

        | Fable.IdentExpr id -> identAsExpr com ctx id |> resolveExpr ctx id.Type returnStrategy

        | Fable.Import({
                           Selector = selector
                           Path = path
                           Kind = _kind
                       },
                       t,
                       r) -> transformImport com ctx r selector path |> resolveExpr ctx t returnStrategy

        | Fable.Test(expr, kind, range) ->
            let expr, stmts = transformTest com ctx range kind expr

            stmts @ (expr |> resolveExpr ctx Fable.Boolean returnStrategy)

        | Fable.Lambda(arg, body, name) ->
            let expr', stmts =
                transformFunctionWithAnnotations com ctx name [ arg ] body
                |||> makeArrowFunctionExpression com ctx name

            stmts @ (expr' |> resolveExpr ctx expr.Type returnStrategy)

        | Fable.Delegate(args, body, name, _) ->
            let expr', stmts =
                transformFunctionWithAnnotations com ctx name args body
                |||> makeArrowFunctionExpression com ctx name

            stmts @ (expr' |> resolveExpr ctx expr.Type returnStrategy)

        | Fable.ObjectExpr([], _, None) -> [] // Remove empty object expression
        | Fable.ObjectExpr(members, t, baseCall) ->
            let expr, stmts = transformObjectExpr com ctx members t baseCall
            stmts @ (expr |> resolveExpr ctx t returnStrategy)

        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "slice" }, _, _), info, typ, _range) ->
            let expr, stmts = transformAsSlice com ctx expr info
            stmts @ resolveExpr ctx typ returnStrategy expr
        | Fable.Call(Fable.Get(expr, Fable.FieldGet { Name = "to_array" }, _, _), info, typ, _range) ->
            let expr, stmts = transformAsArray com ctx expr info
            stmts @ resolveExpr ctx typ returnStrategy expr
        | Fable.Call(callee, info, typ, range) -> transformCallAsStatements com ctx range typ returnStrategy callee info

        | Fable.CurriedApply(callee, args, typ, range) ->
            transformCurriedApplyAsStatements com ctx range typ returnStrategy callee args

        | Fable.Emit(info, t, range) ->
            let e, stmts = transformEmit com ctx range info

            if info.IsStatement then
                stmts @ [ Statement.expr e ] // Ignore the return strategy
            else
                stmts @ resolveExpr ctx t returnStrategy e

        | Fable.Operation(kind, tags, t, range) ->
            let expr, stmts = transformOperation com ctx range kind tags
            stmts @ (expr |> resolveExpr ctx t returnStrategy)

        | Fable.Get(expr, kind, t, range) ->
            let expr, stmts = transformGet com ctx range t expr kind
            stmts @ (expr |> resolveExpr ctx t returnStrategy)

        | Fable.Let(ident, value, body) ->
            match ident, value, body with
            // Transform F# `use` i.e TryCatch as Python `with`
            | { Name = valueName },
              value,
              Fable.TryCatch(body,
                             None,
                             Some(Fable.IfThenElse(_,
                                                   Fable.Call(Fable.Get(Fable.TypeCast(Fable.IdentExpr {
                                                                                                           Name = disposeName
                                                                                                       },
                                                                                       _),
                                                                        Fable.FieldGet { Name = "Dispose" },
                                                                        _t,
                                                                        _),
                                                              _,
                                                              _,
                                                              _),
                                                   _elseExpr,
                                                   _)),
                             _) when valueName = disposeName ->
                let id = Identifier valueName

                let body =
                    com.TransformAsStatements(ctx, Some ResourceManager, body)
                    |> List.choose Helpers.isProductiveStatement

                let value, stmts = com.TransformAsExpr(ctx, value)
                let items = [ WithItem.withItem (value, Expression.name id) ]
                stmts @ [ Statement.with' (items, body) ]
            | _ ->
                let binding = transformBindingAsStatements com ctx ident value

                List.append binding (transformAsStatements com ctx returnStrategy body)

        | Fable.LetRec(bindings, body) ->
            let bindings =
                bindings
                |> Seq.collect (fun (i, v) -> transformBindingAsStatements com ctx i v)
                |> Seq.toList

            List.append bindings (transformAsStatements com ctx returnStrategy body)

        | Fable.Set(expr, kind, typ, value, range) ->
            let expr', stmts = transformSet com ctx range expr typ value kind
            // printfn "transformAsStatements: Fable.Set: %A" (expr', value)
            match expr' with
            | Expression.NamedExpr({
                                       Target = target
                                       Value = value
                                       Loc = _
                                   }) ->
                let nonLocals, ta =
                    match target with
                    | Expression.Name { Id = id } ->
                        let nonLocals = [ ctx.BoundVars.NonLocals([ id ]) |> Statement.nonLocal ]

                        nonLocals, None
                    | Expression.Attribute { Value = Expression.Name { Id = Identifier "self" } } ->
                        let ta, stmts = typeAnnotation com ctx None typ
                        stmts, Some ta
                    | _ -> [], None

                let assignment =
                    match ta with
                    | Some ta -> [ Statement.assign (target, ta, value) ]
                    | _ -> [ Statement.assign ([ target ], value) ]

                nonLocals @ stmts @ assignment
            | _ -> stmts @ (expr' |> resolveExpr ctx expr.Type returnStrategy)
        | Fable.IfThenElse(guardExpr,
                           Fable.Expr.Extended(Fable.ExtendedSet.Debugger, _),
                           Fable.Expr.Value(Fable.ValueKind.Null Fable.Type.Unit, None),
                           r) ->
            // Rewrite `if (guard) { Debugger; null }` to assert (guard)
            let guardExpr', stmts = transformAsExpr com ctx guardExpr
            stmts @ [ Statement.assert' guardExpr' ]
        | Fable.IfThenElse(guardExpr, thenExpr, elseExpr, r) ->
            let asStatement =
                match returnStrategy with
                | None
                | Some ReturnUnit -> true
                | Some(Target _) -> true // Compile as statement so values can be bound
                | Some(Assign _) -> (isPyStatement ctx false thenExpr) || (isPyStatement ctx false elseExpr)
                | Some ResourceManager
                | Some Return ->
                    Option.isSome ctx.TailCallOpportunity
                    || (isPyStatement ctx false thenExpr)
                    || (isPyStatement ctx false elseExpr)

            if asStatement then
                transformIfStatement com ctx r returnStrategy guardExpr thenExpr elseExpr
            else
                let guardExpr', stmts = transformAsExpr com ctx guardExpr
                let thenExpr', stmts' = transformAsExpr com ctx thenExpr
                let elseExpr', stmts'' = transformAsExpr com ctx elseExpr

                stmts
                @ stmts'
                @ stmts''
                @ (Expression.ifExp (guardExpr', thenExpr', elseExpr', ?loc = r)
                   |> resolveExpr ctx thenExpr.Type returnStrategy)

        | Fable.Sequential statements ->
            let lasti = (List.length statements) - 1

            statements
            |> List.mapiToArray (fun i statement ->
                let ret =
                    if i < lasti then
                        None
                    else
                        returnStrategy

                com.TransformAsStatements(ctx, ret, statement)
            )
            |> List.concat

        | Fable.TryCatch(body, catch, finalizer, r) ->
            transformTryCatch com ctx r returnStrategy (body, catch, finalizer)

        | Fable.DecisionTree(expr, targets) -> transformDecisionTreeAsStatements com ctx returnStrategy targets expr

        | Fable.DecisionTreeSuccess(idx, boundValues, _) ->
            transformDecisionTreeSuccessAsStatements com ctx returnStrategy idx boundValues

        | Fable.WhileLoop(TransformExpr com ctx (guard, stmts), body, range) ->
            stmts
            @ [ Statement.while' (guard, transformBlock com ctx None body, ?loc = range) ]

        | Fable.ForLoop(var,
                        TransformExpr com ctx (start, _stmts),
                        TransformExpr com ctx (limit, _stmts'),
                        body,
                        isUp,
                        _range) ->
            let limit, step =
                if isUp then
                    let limit = Expression.binOp (limit, Add, Expression.intConstant 1) // Python `range` has exclusive end.

                    limit, 1
                else
                    let limit = Expression.binOp (limit, Sub, Expression.intConstant 1) // Python `range` has exclusive end.

                    limit, -1

            let step = Expression.intConstant step

            let iter =
                Expression.call (Expression.name (Identifier "range"), args = [ start; limit; step ])

            let body = transformBlock com ctx None body
            let target = com.GetIdentifierAsExpr(ctx, var.Name)

            [ Statement.for' (target = target, iter = iter, body = body) ]

    let transformFunction
        com
        ctx
        name
        (args: Fable.Ident list)
        (body: Fable.Expr)
        (repeatedGenerics: Set<string>)
        : Arguments * Statement list
        =
        let tailcallChance =
            Option.map (fun name -> NamedTailCallOpportunity(com, ctx, name, args) :> ITailCallOpportunity) name

        let args = FSharp2Fable.Util.discardUnitArg args

        /// Removes `_mut` or `_mut_1` suffix from the identifier name
        let cleanName (input: string) =
            Regex.Replace(input, @"_mut(_\d+)?$", "")

        // For Python we need to append the TC-arguments to any declared (arrow) function inside the while-loop of the
        // TCO. We will set them as default values to themselves e.g `i=i` to capture the value and not the variable.
        let tcArgs, tcDefaults =
            match ctx.TailCallOpportunity with
            | Some tc ->
                tc.Args
                |> List.choose (fun arg ->
                    let (Identifier name) = arg.Arg
                    let name = cleanName name

                    match name with
                    | "tupled_arg_m" -> None // Remove these arguments (not sure why)
                    | _ ->
                        let annotation =
                            // Cleanup type annotations to avoid non-repeated generics
                            match arg.Annotation with
                            | Some(Expression.Name { Id = Identifier _name }) -> arg.Annotation
                            | Some(Expression.Subscript {
                                                            Value = value
                                                            Slice = Expression.Name { Id = Identifier name }
                                                        }) when name.StartsWith("_", StringComparison.Ordinal) ->
                                Expression.subscript (value, stdlibModuleAnnotation com ctx "typing" "Any" [])
                                |> Some
                            | _ -> Some(stdlibModuleAnnotation com ctx "typing" "Any" [])

                        (Arg.arg (name, ?annotation = annotation), Expression.name name) |> Some
                )
                |> List.unzip
            | _ -> [], []

        let declaredVars = ResizeArray()
        let mutable isTailCallOptimized = false

        let argTypes = args |> List.map (fun id -> id.Type)
        let genTypeParams = Util.getGenericTypeParams (argTypes @ [ body.Type ])
        let newTypeParams = Set.difference genTypeParams ctx.ScopedTypeParams

        let ctx =
            { ctx with
                TailCallOpportunity = tailcallChance
                HoistVars =
                    fun ids ->
                        declaredVars.AddRange(ids)
                        true
                OptimizeTailCall = fun () -> isTailCallOptimized <- true
                BoundVars = ctx.BoundVars.EnterScope()
                ScopedTypeParams = Set.union ctx.ScopedTypeParams newTypeParams
            }

        let body =
            if body.Type = Fable.Unit then
                transformBlock com ctx (Some ReturnUnit) body
            elif isPyStatement ctx (Option.isSome tailcallChance) body then
                transformBlock com ctx (Some Return) body
            else
                transformAsExpr com ctx body |> wrapExprInBlockWithReturn

        let isUnit =
            List.tryLast args
            |> Option.map (
                function
                | { Type = Fable.GenericParam _ } -> true
                | _ -> false
            )
            |> Option.defaultValue false

        let args, defaults, body =
            match isTailCallOptimized, tailcallChance with
            | true, Some tc ->
                // 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, _ = typeAnnotation com ctx (Some repeatedGenerics) _id.Type

                        Arg.arg (id, annotation = ta)
                    )

                let varDecls =
                    List.zip args tc.Args
                    |> List.map (fun (id, { Arg = Identifier tcArg }) ->
                        ident com ctx id, Some(com.GetIdentifierAsExpr(ctx, tcArg))
                    )
                    |> multiVarDeclaration ctx

                let body = varDecls @ body
                // Make sure we don't get trapped in an infinite loop, see #1624
                let body = body @ [ Statement.break' () ]

                args', [], Statement.while' (Expression.boolConstant true, body) |> List.singleton
            | _ ->
                // Make sure all of the last optional arguments will accept None as their default value
                let defaults =
                    args
                    |> List.rev
                    |> List.takeWhile (fun arg ->
                        match arg.Type with
                        | Fable.Any
                        | Fable.Option _ -> true
                        | _ -> false
                    )
                    |> List.map (fun _ -> Expression.none)

                let args' =
                    args
                    |> List.map (fun id ->
                        let ta, _ = typeAnnotation com ctx (Some repeatedGenerics) id.Type

                        Arg.arg (ident com ctx id, annotation = ta)
                    )

                args', defaults, body

        let arguments =
            match args, isUnit with
            | [], _ ->
                Arguments.arguments (
                    args = Arg.arg (Identifier("__unit"), annotation = Expression.name "None") :: tcArgs,
                    defaults = Expression.none :: tcDefaults
                )
            // So we can also receive unit
            | [ arg ], true ->
                let optional =
                    match arg.Annotation with
                    | Some typeArg -> Expression.binOp (typeArg, BitOr, Expression.name "None") |> Some
                    | None -> None

                let args = [ { arg with Annotation = optional } ]

                Arguments.arguments (args @ tcArgs, defaults = Expression.none :: tcDefaults)
            | _ -> Arguments.arguments (args @ tcArgs, defaults = defaults @ tcDefaults)

        arguments, body

    // Declares a Python entry point, i.e `if __name__ == "__main__"`
    let declareEntryPoint (com: IPythonCompiler) (ctx: Context) (funcExpr: Expression) =
        com.GetImportExpr(ctx, "sys") |> ignore
        let args = emitExpression None "sys.argv[1:]" []

        let test =
            Expression.compare (
                Expression.name "__name__",
                [ ComparisonOperator.Eq ],
                [ Expression.stringConstant "__main__" ]
            )

        let main = Expression.call (funcExpr, [ args ]) |> Statement.expr |> List.singleton

        Statement.if' (test, main)

    let declareModuleMember (com: IPythonCompiler) ctx _isPublic (membName: Identifier) typ (expr: Expression) =
        let (Identifier name) = membName

        if com.OutputType = OutputType.Library then
            com.AddExport name |> ignore

        let name = Expression.name membName
        varDeclaration ctx name typ expr

    let makeEntityTypeParamDecl (com: IPythonCompiler) ctx (ent: Fable.Entity) =
        getEntityGenParams ent |> makeTypeParamDecl com ctx

    let getUnionFieldsAsIdents (_com: IPythonCompiler) _ctx (_ent: Fable.Entity) =
        let tagId = makeTypedIdent (Fable.Number(Int32, Fable.NumberInfo.Empty)) "tag"

        let fieldsId = makeTypedIdent (Fable.Array(Fable.Any, Fable.MutableArray)) "fields"

        [| tagId; fieldsId |]

    let getEntityFieldsAsIdents _com (ent: Fable.Entity) =
        ent.FSharpFields
        |> Seq.map (fun field ->
            let name =
                (Naming.toSnakeCase field.Name, Naming.NoMemberPart)
                ||> Naming.sanitizeIdent Naming.pyBuiltins.Contains

            let typ = field.FieldType

            { makeTypedIdent typ name with IsMutable = field.IsMutable }
        )
        |> Seq.toArray

    let getEntityFieldsAsProps (com: IPythonCompiler) ctx (ent: Fable.Entity) =
        if ent.IsFSharpUnion then
            getUnionFieldsAsIdents com ctx ent |> Array.map (identAsExpr com ctx)
        else
            ent.FSharpFields
            |> Seq.map (fun field ->
                let prop = memberFromName com ctx field.Name
                prop
            )
            |> Seq.toArray

    let declareDataClassType
        (com: IPythonCompiler)
        (ctx: Context)
        (ent: Fable.Entity)
        (entName: string)
        (consArgs: Arguments)
        (_isOptional: bool)
        (_consBody: Statement list)
        (baseExpr: Expression option)
        (classMembers: Statement list)
        _slotMembers
        =
        let name = com.GetIdentifier(ctx, entName)

        let props =
            consArgs.Args
            |> List.map (fun arg ->
                let any _ =
                    stdlibModuleAnnotation com ctx "typing" "Any" []

                let annotation = arg.Annotation |> Option.defaultWith any

                Statement.assign (Expression.name arg.Arg, annotation = annotation)
            )

        let generics = makeEntityTypeParamDecl com ctx ent
        let bases = baseExpr |> Option.toList

        let classBody =
            let body = [ yield! props; yield! classMembers ]

            match body with
            | [] -> [ Statement.ellipsis ]
            | _ -> body

        let dataClass = com.GetImportExpr(ctx, "dataclasses", "dataclass")

        let decorators =
            [
                Expression.call (
                    dataClass,
                    kw =
                        [
                            Keyword.keyword (Identifier "eq", Expression.boolConstant false)
                            Keyword.keyword (Identifier "repr", Expression.boolConstant false)
                            Keyword.keyword (Identifier "slots", Expression.boolConstant true)
                        ]
                )
            ]

        [
            Statement.classDef (name, body = classBody, decoratorList = decorators, bases = bases @ generics)
        ]

    let declareClassType
        (com: IPythonCompiler)
        (ctx: Context)
        (ent: Fable.Entity)
        (entName: string)
        (consArgs: Arguments)
        (isOptional: bool)
        (consBody: Statement list)
        (baseExpr: Expression option)
        (classMembers: Statement list)
        slotMembers
        =
        // printfn "declareClassType: %A" consBody
        let generics = makeEntityTypeParamDecl com ctx ent
        let classCons = makeClassConstructor consArgs isOptional consBody

        let classFields = slotMembers // TODO: annotations
        let classMembers = classCons @ classMembers
        //printfn "ClassMembers: %A" classMembers
        let classBody =
            let body = [ yield! classFields; yield! classMembers ]

            match body with
            | [] -> [ Statement.ellipsis ]
            | _ -> body


        let interfaces, stmts =
            // We only use a few interfaces as base classes. The rest is handled as Python protocols (PEP 544) to avoid a massive
            // inheritance tree that will prevent Python of finding a consistent method resolution order.
            let allowedInterfaces = [ "IDisposable" ]

            ent.AllInterfaces
            |> List.ofSeq
            |> List.filter (fun int ->
                let name = Helpers.removeNamespace (int.Entity.FullName)
                allowedInterfaces |> List.contains name
            )
            |> List.map (fun int ->
                let genericArgs =
                    match int.GenericArgs with
                    | [ Fable.DeclaredType({ FullName = fullName }, _genericArgs) ] when
                        Helpers.removeNamespace (fullName) = entName
                        ->
                        [ Fable.Type.Any ]
                    | args -> args

                let expr, stmts = makeEntityTypeAnnotation com ctx int.Entity genericArgs None

                expr, stmts
            )
            |> Helpers.unzipArgs

        let bases = baseExpr |> Option.toList
        let name = com.GetIdentifier(ctx, Naming.toSnakeCase entName)

        stmts
        @ [
            Statement.classDef (name, body = classBody, bases = bases @ interfaces @ generics)
        ]

    let createSlotsForRecordType (com: IPythonCompiler) ctx (classEnt: Fable.Entity) =
        let strFromIdent (ident: Identifier) = ident.Name

        if classEnt.IsValueType then
            let elements =
                getEntityFieldsAsProps com ctx classEnt
                |> Array.map (nameFromKey com ctx >> strFromIdent >> Expression.stringConstant)
                |> Array.toList

            let slots = Expression.list (elements, Load)

            [ Statement.assign ([ Expression.name ("__slots__", Store) ], slots) ]
        else
            []

    let declareType
        (com: IPythonCompiler)
        (ctx: Context)
        (ent: Fable.Entity)
        (entName: string)
        (consArgs: Arguments)
        (isOptional: bool)
        (consBody: Statement list)
        (baseExpr: Expression option)
        (classMembers: Statement list)
        : Statement list
        =
        let slotMembers = createSlotsForRecordType com ctx ent

        let typeDeclaration =
            match ent.IsFSharpRecord with
            | true ->
                declareDataClassType com ctx ent entName consArgs isOptional consBody baseExpr classMembers slotMembers
            | false ->
                declareClassType com ctx ent entName consArgs isOptional consBody baseExpr classMembers slotMembers

        let reflectionDeclaration, stmts =
            let ta = fableModuleAnnotation com ctx "Reflection" "TypeInfo" []

            let genArgs =
                Array.init ent.GenericParameters.Length (fun i -> "gen" + string<int> i |> makeIdent)

            let args =
                genArgs
                |> Array.mapToList (fun id -> Arg.arg (ident com ctx id, annotation = ta))

            let args = Arguments.arguments args
            let generics = genArgs |> Array.mapToList (identAsExpr com ctx)

            let body, stmts = transformReflectionInfo com ctx None ent generics

            let expr, stmts' = makeFunctionExpression com ctx None (args, body, [], ta)

            let name =
                com.GetIdentifier(ctx, Naming.toSnakeCase entName + Naming.reflectionSuffix)

            expr |> declareModuleMember com ctx ent.IsPublic name None, stmts @ stmts'

        stmts @ typeDeclaration @ reflectionDeclaration

    let transformModuleFunction
        (com: IPythonCompiler)
        ctx
        (info: Fable.MemberFunctionOrValue)
        (membName: string)
        args
        body
        =
        let args, body', returnType =
            getMemberArgsAndBody com ctx (NonAttached membName) info.HasSpread args body

        let name = com.GetIdentifier(ctx, membName)
        let stmt = createFunction name args body' [] returnType info.XmlDoc
        let expr = Expression.name name

        info.Attributes
        |> Seq.exists (fun att -> att.Entity.FullName = Atts.entryPoint)
        |> function
            | true -> [ stmt; declareEntryPoint com ctx expr ]
            | false ->
                if com.OutputType = OutputType.Library then
                    com.AddExport membName |> ignore

                [ stmt ]

    let transformAction (com: IPythonCompiler) ctx expr =
        let statements = transformAsStatements com ctx None expr
        // let hasVarDeclarations =
        //     statements |> List.exists (function
        //         | Declaration(_) -> true
        //         | _ -> false)
        // if hasVarDeclarations then
        //     [ Expression.call(Expression.functionExpression([||], BlockStatement(statements)), [||])
        //       |> Statement.expr |> PrivateModuleDeclaration ]
        //else
        statements

    let nameFromKey (com: IPythonCompiler) (ctx: Context) key =
        match key with
        | Expression.Name { Id = ident } -> ident
        | Expression.Constant(value = StringLiteral name) -> com.GetIdentifier(ctx, name)
        | name -> failwith $"Not a valid name: {name}"

    let transformAttachedProperty
        (com: IPythonCompiler)
        ctx
        (info: Fable.MemberFunctionOrValue)
        (memb: Fable.MemberDecl)
        =
        let isStatic = not info.IsInstance
        let isGetter = info.IsGetter

        let decorators =
            [
                if isStatic then
                    Expression.name "staticmethod"
                elif isGetter then
                    Expression.name "property"
                else
                    Expression.name $"{memb.Name}.setter"
            ]

        let args, body, returnType =
            getMemberArgsAndBody com ctx (Attached isStatic) false memb.Args memb.Body

        let key = memberFromName com ctx memb.Name |> nameFromKey com ctx

        let arguments =
            if isStatic then
                { args with Args = [] }
            else
                let self = Arg.arg "self"
                { args with Args = self :: args.Args }

        // Python do not support static getters, so make it a function instead
        Statement.functionDef (key, arguments, body = body, decoratorList = decorators, returns = returnType)
        |> List.singleton

    let transformAttachedMethod
        (com: IPythonCompiler)
        ctx
        (info: Fable.MemberFunctionOrValue)
        (memb: Fable.MemberDecl)
        =
        // printfn "transformAttachedMethod: %A" memb

        let isStatic = not info.IsInstance

        let decorators =
            if isStatic then
                [ Expression.name "staticmethod" ]
            else
                []

        let makeMethod name args body decorators returnType =
            let key = memberFromName com ctx name |> nameFromKey com ctx

            Statement.functionDef (key, args, body = body, decoratorList = decorators, returns = returnType)

        let args, body, returnType =
            getMemberArgsAndBody com ctx (Attached isStatic) info.HasSpread memb.Args memb.Body

        let self = Arg.arg "self"

        let arguments =
            if isStatic then
                args
            else
                { args with Args = self :: args.Args }

        [
            yield makeMethod memb.Name arguments body decorators returnType
            if info.FullName = "System.Collections.Generic.IEnumerable.GetEnumerator" then
                yield
                    makeMethod
                        "__iter__"
                        (Arguments.arguments [ self ])
                        (enumerator2iterator com ctx)
                        decorators
                        returnType
        ]

    let transformUnion (com: IPythonCompiler) ctx (ent: Fable.Entity) (entName: string) classMembers =
        let fieldIds = getUnionFieldsAsIdents com ctx ent

        let args, isOptional =
            let args =
                fieldIds[0]
                |> ident com ctx
                |> (fun id ->
                    let ta, _ = typeAnnotation com ctx None fieldIds[0].Type
                    Arg.arg (id, annotation = ta)
                )
                |> List.singleton

            let varargs =
                fieldIds[1]
                |> ident com ctx
                |> (fun id ->
                    let gen = getGenericTypeParams [ fieldIds[1].Type ] |> Set.toList |> List.tryHead

                    let ta = Expression.name (gen |> Option.defaultValue "Any")
                    Arg.arg (id, annotation = ta)
                )

            let isOptional = Helpers.isOptional fieldIds
            Arguments.arguments (args = args, vararg = varargs), isOptional

        let body =
            [
                yield callSuperAsStatement []
                yield!
                    fieldIds
                    |> Array.map (fun id ->
                        let left = get com ctx None thisExpr id.Name false

                        let right =
                            match id.Type with
                            | Fable.Number _ ->
                                Expression.boolOp (
                                    BoolOperator.Or,
                                    [ identAsExpr com ctx id; Expression.intConstant 0 ]
                                )
                            | Fable.Array _ ->
                                // Convert varArg from tuple to list. TODO: we might need to do this other places as well.
                                Expression.call (Expression.name "list", [ identAsExpr com ctx id ])
                            | _ -> identAsExpr com ctx id

                        let ta, _ = typeAnnotation com ctx None id.Type
                        Statement.assign (left, ta, right)
                    )
            ]

        let cases =
            let expr, stmts =
                ent.UnionCases
                |> Seq.map (getUnionCaseName >> makeStrConst)
                |> Seq.toList
                |> makeList com ctx

            let name = Identifier("cases")
            let body = stmts @ [ Statement.return' expr ]
            let decorators = [ Expression.name "staticmethod" ]

            let returnType =
                Expression.subscript (Expression.name "list", Expression.name "str")

            Statement.functionDef (
                name,
                Arguments.arguments (),
                body = body,
                returns = returnType,
                decoratorList = decorators
            )

        let baseExpr = libValue com ctx "types" "Union" |> Some
        let classMembers = List.append [ cases ] classMembers

        declareType com ctx ent entName args isOptional body baseExpr classMembers

    let transformClassWithCompilerGeneratedConstructor
        (com: IPythonCompiler)
        ctx
        (ent: Fable.Entity)
        (entName: string)
        classMembers
        =
        // printfn "transformClassWithCompilerGeneratedConstructor"
        let fieldIds = getEntityFieldsAsIdents com ent

        let args =
            fieldIds
            |> Array.map (fun id -> com.GetIdentifier(ctx, id.Name) |> Expression.name)

        let isOptional =
            Helpers.isOptional fieldIds || ent.IsFSharpRecord || ent.IsValueType

        let baseExpr =
            if ent.IsFSharpExceptionDeclaration then
                libValue com ctx "types" "FSharpException" |> Some
            elif ent.IsFSharpRecord || ent.IsValueType then
                libValue com ctx "types" "Record" |> Some
            else
                None

        let body =
            [
                if Option.isSome baseExpr then
                    yield callSuperAsStatement []

                yield!
                    (ent.FSharpFields
                     |> List.collecti (fun i field ->
                         let left = get com ctx None thisExpr (Naming.toSnakeCase field.Name) false

                         let right = args[i] |> wrapIntExpression field.FieldType

                         assign None left right |> exprAsStatement ctx
                     ))
            ]

        let args =
            fieldIds
            |> Array.mapToList (fun id ->
                let ta, _ = typeAnnotation com ctx None id.Type
                Arg.arg (ident com ctx id, annotation = ta)
            )
            |> (fun args -> Arguments.arguments (args = args))

        declareType com ctx ent entName args isOptional body baseExpr classMembers

    let transformClassWithPrimaryConstructor
        (com: IPythonCompiler)
        ctx
        (classDecl: Fable.ClassDecl)
        (classMembers: Statement list)
        (cons: Fable.MemberDecl)
        =
        // printfn "transformClassWithPrimaryConstructor: %A" classDecl
        let classEnt = com.GetEntity(classDecl.Entity)

        let classIdent = Expression.name (com.GetIdentifier(ctx, classDecl.Name))

        let consArgs, consBody, _returnType =
            let info = com.GetMember(cons.MemberRef)

            getMemberArgsAndBody com ctx ClassConstructor info.HasSpread cons.Args cons.Body

        let isOptional = Helpers.isOptional (cons.Args |> Array.ofList)

        // Change exposed constructor's return type from None to entity type.
        let returnType =
            let availableGenerics =
                cons.Args |> List.map (fun arg -> arg.Type) |> getGenericTypeParams

            let genParams = getEntityGenParams classEnt

            makeGenericTypeAnnotation' com ctx classDecl.Name (genParams |> List.ofSeq) (Some availableGenerics)

        let exposedCons =
            let argExprs = consArgs.Args |> List.map (fun p -> Expression.identifier p.Arg)

            let exposedConsBody = Expression.call (classIdent, argExprs)
            let name = com.GetIdentifier(ctx, cons.Name)
            makeFunction name (consArgs, exposedConsBody, [], returnType)

        let baseExpr, consBody =
            classDecl.BaseCall
            |> extractBaseExprFromBaseCall com ctx classEnt.BaseType
            |> Option.orElseWith (fun () ->
                if classEnt.IsValueType then
                    Some(libValue com ctx "Types" "Record", ([], [], []))
                else
                    None
            )
            |> Option.map (fun (baseExpr, (baseArgs, _kw, stmts)) ->
                let consBody = stmts @ [ callSuperAsStatement baseArgs ] @ consBody

                Some baseExpr, consBody
            )
            |> Option.defaultValue (None, consBody)

        [
            yield! declareType com ctx classEnt classDecl.Name consArgs isOptional consBody baseExpr classMembers
            exposedCons
        ]

    let transformInterface (com: IPythonCompiler) ctx (classEnt: Fable.Entity) (_classDecl: Fable.ClassDecl) =
        // printfn "transformInterface"
        let classIdent = com.GetIdentifier(ctx, Helpers.removeNamespace classEnt.FullName)

        let members =
            classEnt.MembersFunctionsAndValues
            |> Seq.filter (fun memb -> not memb.IsProperty)
            |> List.ofSeq
            |> List.groupBy (fun memb -> memb.DisplayName)
            // Remove duplicate method when we have getters and setters
            |> List.collect (fun (_, gr) ->
                gr
                |> List.filter (fun memb -> gr.Length = 1 || (memb.IsGetter || memb.IsSetter))
            )

        let classMembers =
            [
                for memb in members do
                    let name = memb.DisplayName |> Naming.toSnakeCase |> Helpers.clean

                    let abstractMethod = com.GetImportExpr(ctx, "abc", "abstractmethod")

                    let decorators =
                        [
                            if memb.IsValue || memb.IsGetter then
                                Expression.name "property"
                            if memb.IsSetter then
                                Expression.name $"{name}.setter"

                            abstractMethod
                        ] // Must be after @property

                    let name = com.GetIdentifier(ctx, name)

                    let args =
                        let args =
                            [
                                if memb.IsInstance then
                                    Arg.arg "self"
                                for n, parameterGroup in memb.CurriedParameterGroups |> Seq.indexed do
                                    for m, pg in parameterGroup |> Seq.indexed do
                                        let ta, _ = typeAnnotation com ctx None pg.Type

                                        Arg.arg (pg.Name |> Option.defaultValue $"__arg{n + m}", annotation = ta)
                            ]

                        Arguments.arguments args

                    let returnType, _ = typeAnnotation com ctx None memb.ReturnParameter.Type

                    let body = [ Statement.ellipsis ]

                    Statement.functionDef (name, args, body, returns = returnType, decoratorList = decorators)

                if members.IsEmpty then
                    Statement.Pass
            ]

        let bases =
            [
                let interfaces =
                    classEnt.AllInterfaces
                    |> List.ofSeq
                    |> List.map (fun int -> int.Entity)
                    |> List.filter (fun ent -> ent.FullName <> classEnt.FullName)

                for ref in interfaces do
                    let entity = com.TryGetEntity(ref)

                    match entity with
                    | Some entity ->
                        let expr, _stmts = makeEntityTypeAnnotation com ctx entity.Ref [] None

                        expr
                    | None -> ()

                // Only add Protocol base if no interfaces (since the included interfaces will be protocols themselves)
                if List.isEmpty interfaces then
                    com.GetImportExpr(ctx, "typing", "Protocol")

                for gen in classEnt.GenericParameters do
                    Expression.subscript (com.GetImportExpr(ctx, "typing", "Generic"), com.AddTypeVar(ctx, gen.Name))
            ]

        [ Statement.classDef (classIdent, body = classMembers, bases = bases) ]

    let rec transformDeclaration (com: IPythonCompiler) ctx (decl: Fable.Declaration) =
        // printfn "transformDeclaration: %A" decl
        // printfn "ctx.UsedNames: %A" ctx.UsedNames

        let withCurrentScope (ctx: Context) (usedNames: Set<string>) f =
            let ctx =
                { ctx with UsedNames = { ctx.UsedNames with CurrentDeclarationScope = HashSet usedNames } }

            let result = f ctx

            ctx.UsedNames.DeclarationScopes.UnionWith(ctx.UsedNames.CurrentDeclarationScope)

            result

        match decl with
        | Fable.ModuleDeclaration decl -> decl.Members |> List.collect (transformDeclaration com ctx)

        | Fable.ActionDeclaration decl ->
            withCurrentScope ctx decl.UsedNames
            <| fun ctx -> transformAction com ctx decl.Body

        | Fable.MemberDeclaration decl ->
            withCurrentScope ctx decl.UsedNames
            <| fun ctx ->
                let info = com.GetMember(decl.MemberRef)

                let decls =
                    if info.IsValue then
                        let value, stmts = transformAsExpr com ctx decl.Body
                        let name = com.GetIdentifier(ctx, Naming.toSnakeCase decl.Name)
                        let ta, _ = typeAnnotation com ctx None decl.Body.Type

                        stmts @ declareModuleMember com ctx info.IsPublic name (Some ta) value
                    else
                        transformModuleFunction com ctx info decl.Name decl.Args decl.Body

                decls

        | Fable.ClassDeclaration decl ->
            // printfn "Class: %A" decl
            let ent = com.GetEntity(decl.Entity)

            let classMembers =
                decl.AttachedMembers
                |> List.collect (fun memb ->
                    withCurrentScope ctx memb.UsedNames
                    <| fun ctx ->
                        let info =
                            memb.ImplementedSignatureRef
                            |> Option.map com.GetMember
                            |> Option.defaultWith (fun () -> com.GetMember(memb.MemberRef))

                        if not memb.IsMangled && (info.IsGetter || info.IsSetter) then
                            transformAttachedProperty com ctx info memb
                        else
                            transformAttachedMethod com ctx info memb
                )

            match ent, decl.Constructor with
            | ent, _ when ent.IsInterface -> transformInterface com ctx ent decl
            | ent, _ when ent.IsFSharpUnion -> transformUnion com ctx ent decl.Name classMembers
            | _, Some cons ->
                withCurrentScope ctx cons.UsedNames
                <| fun ctx -> transformClassWithPrimaryConstructor com ctx decl classMembers cons
            | _, None -> transformClassWithCompilerGeneratedConstructor com ctx ent decl.Name classMembers

    let transformTypeVars (com: IPythonCompiler) ctx (typeVars: HashSet<string>) =
        [
            for var in typeVars do
                let targets = Expression.name var |> List.singleton
                let value = com.GetImportExpr(ctx, "typing", "TypeVar")
                let args = Expression.stringConstant var |> List.singleton
                let value = Expression.call (value, args)
                Statement.assign (targets, value)
        ]

    let transformExports (_com: IPythonCompiler) _ctx (exports: HashSet<string>) =
        let exports = exports |> List.ofSeq

        match exports with
        | [] -> []
        | _ ->
            let all = Expression.name "__all__"

            let names = exports |> List.map Expression.stringConstant |> Expression.list

            [ Statement.assign ([ all ], names) ]

    let transformImports (_com: IPythonCompiler) (imports: Import list) : Statement list =
        let imports =
            imports
            |> List.map (fun im ->
                let moduleName = im.Module

                match im.Name with
                | Some "*"
                | Some "default" ->
                    let (Identifier local) = im.LocalIdent

                    if moduleName <> local then
                        Some moduleName, Alias.alias im.LocalIdent
                    else
                        None, Alias.alias im.LocalIdent
                | Some name ->
                    let name = Naming.toSnakeCase name

                    Some moduleName, Alias.alias (Identifier(Helpers.clean name), asname = im.LocalIdent)
                | None -> None, Alias.alias (Identifier(moduleName), asname = im.LocalIdent)
            )
            |> List.groupBy fst
            |> List.map (fun (a, b) -> a, List.map snd b)
            |> List.sortBy (fun name ->
                let name =
                    match name with
                    | Some moduleName, _ -> moduleName.ToLower()
                    | None, { Name = name } :: _ -> name.Name
                    | _ -> ""

                match name with
                | name when name.StartsWith("__", StringComparison.Ordinal) -> "A" + name
                | name when name.StartsWith("fable", StringComparison.Ordinal) -> "C" + name
                | name when name.StartsWith(".", StringComparison.Ordinal) -> "D" + name
                | _ -> "B" + name
            )

        [
            for moduleName, aliases in imports do
                match moduleName with
                | Some name -> Statement.importFrom (Some(Identifier(name)), aliases)
                | None ->
                    // Do not put multiple imports on a single line. flake8(E401)
                    for alias in aliases do
                        Statement.import [ alias ]
        ]

    let getIdentForImport (ctx: Context) (moduleName: string) (name: string option) =
        // printfn "getIdentForImport: %A" (moduleName, name)
        match name with
        | None -> Path.GetFileNameWithoutExtension(moduleName)
        | Some name -> name |> Naming.toSnakeCase |> getUniqueNameInRootScope ctx
        |> Identifier

module Compiler =
    open Util

    type PythonCompiler(com: Compiler) =
        let onlyOnceWarnings = HashSet<string>()
        let imports = Dictionary<string, Import>()
        let exports: HashSet<string> = HashSet()
        let typeVars: HashSet<string> = HashSet()

        interface IPythonCompiler with
            member _.WarnOnlyOnce(msg, ?range) =
                if onlyOnceWarnings.Add(msg) then
                    addWarning com [] range msg

            member _.GetImportExpr(ctx, moduleName, ?name, ?r) =
                // printfn "GetImportExpr: %A" (moduleName, name)
                let name =
                    match name with
                    | None
                    | Some null -> ""
                    | Some name -> name.Trim()

                let isQualifiedPythonImport =
                    match name with
                    | ""
                    | "default"
                    | "*" -> false
                    | _ -> true

                let cachedName =
                    moduleName
                    + "::"
                    + if isQualifiedPythonImport then
                          name
                      else
                          ""

                match imports.TryGetValue(cachedName) with
                | true, i -> i.LocalIdent |> Expression.identifier
                | false, _ ->
                    let local_id =
                        if isQualifiedPythonImport then
                            Some name
                        else
                            None
                        |> getIdentForImport ctx moduleName

                    let importName =
                        match name with
                        | _ when not isQualifiedPythonImport -> None
                        | Naming.placeholder ->
                            "`importMember` must be assigned to a variable" |> addError com [] r
                            Some name
                        | _ -> Some name

                    let i =
                        {
                            Name = importName
                            Module = moduleName
                            LocalIdent = local_id
                        }

                    imports.Add(cachedName, i)

                    // If the import member is empty we understand this is done for side-effects only
                    if name = "" then
                        Expression.none
                    else
                        Expression.identifier local_id

            member _.GetAllImports() =
                imports.Values :> Import seq |> List.ofSeq

            member _.GetAllTypeVars() = typeVars
            member _.GetAllExports() = exports

            member _.AddTypeVar(ctx, name: string) =
                // TypeVars should be private and uppercase. For auto-generated (inferred) generics we use a double-undercore.
                let name =
                    let name = name.ToUpperInvariant() |> Helpers.clean
                    $"_{name}"

                // For object expressions we need to create a new type scope so we make an extra padding to ensure uniqueness
                let name = name.PadRight(ctx.TypeParamsScope + name.Length, '_')
                typeVars.Add name |> ignore

                ctx.UsedNames.DeclarationScopes.Add(name) |> ignore

                Expression.name name

            member _.AddExport(name: string) =
                exports.Add name |> ignore
                Expression.name name

            member bcom.TransformAsExpr(ctx, e) = transformAsExpr bcom ctx e

            member bcom.TransformAsStatements(ctx, ret, e) = transformAsStatements bcom ctx ret e

            member bcom.TransformFunction(ctx, name, args, body, generics) =
                transformFunction bcom ctx name args body generics

            member bcom.TransformImport(ctx, selector, path) =
                transformImport bcom ctx None selector path

            member bcom.GetIdentifier(ctx, name) = getIdentifier bcom ctx name

            member bcom.GetIdentifierAsExpr(ctx, name) =
                getIdentifier bcom ctx name |> Expression.name

        interface Compiler with
            member _.Options = com.Options
            member _.Plugins = com.Plugins
            member _.LibraryDir = com.LibraryDir
            member _.CurrentFile = com.CurrentFile
            member _.OutputDir = com.OutputDir
            member _.OutputType = com.OutputType
            member _.ProjectFile = com.ProjectFile
            member _.SourceFiles = com.SourceFiles
            member _.IncrementCounter() = com.IncrementCounter()

            member _.IsPrecompilingInlineFunction = com.IsPrecompilingInlineFunction

            member _.WillPrecompileInlineFunction(file) = com.WillPrecompileInlineFunction(file)

            member _.GetImplementationFile(fileName) = com.GetImplementationFile(fileName)

            member _.GetRootModule(fileName) = com.GetRootModule(fileName)
            member _.TryGetEntity(fullName) = com.TryGetEntity(fullName)
            member _.GetInlineExpr(fullName) = com.GetInlineExpr(fullName)

            member _.AddWatchDependency(fileName) = com.AddWatchDependency(fileName)

            member _.AddLog(msg, severity, ?range, ?fileName: string, ?tag: string) =
                com.AddLog(msg, severity, ?range = range, ?fileName = fileName, ?tag = tag)

    let makeCompiler com = PythonCompiler(com)

    let transformFile (com: Compiler) (file: Fable.File) =
        let com = makeCompiler com :> IPythonCompiler

        let declScopes =
            let hs = HashSet()

            for decl in file.Declarations do
                hs.UnionWith(decl.UsedNames)

            hs

        let ctx =
            {
                File = file
                UsedNames =
                    {
                        RootScope = HashSet file.UsedNamesInRootScope
                        DeclarationScopes = declScopes
                        CurrentDeclarationScope = Unchecked.defaultof<_>
                    }
                BoundVars =
                    {
                        EnclosingScope = HashSet()
                        LocalScope = HashSet()
                        Inceptions = 0
                    }
                DecisionTargets = []
                HoistVars = fun _ -> false
                TailCallOpportunity = None
                OptimizeTailCall = fun () -> ()
                ScopedTypeParams = Set.empty
                TypeParamsScope = 0
            }

        //printfn "file: %A" file.Declarations
        let rootDecls = List.collect (transformDeclaration com ctx) file.Declarations

        let rootComment =
            com.GetRootModule(com.CurrentFile)
            |> snd
            |> Option.bind FSharp2Fable.TypeHelpers.tryGetXmlDoc

        let typeVars = com.GetAllTypeVars() |> transformTypeVars com ctx
        let importDecls = com.GetAllImports() |> transformImports com
        let exports = com.GetAllExports() |> transformExports com ctx
        let body = importDecls @ typeVars @ rootDecls @ exports
        Module.module' (body, ?comment = rootComment)