Direct fn calls: disable for cyclic calls

[Janiczek]

Quick Summary: Cyclic functions were not correctly analyzed for makeArgLookup (finding the number of arguments of a function).

SSCCE

module Main exposing (main)

import Html exposing (Html)


main : Html msg
main =
    Html.div []
        [ Html.text (a1 1 1)
        , Html.text (a2 1 1)
        , Html.text (b1 3 4 5)
        , Html.text (b2 1 2 3 4 5)
        ]


a1 : Int -> Int -> String
a1 =
    a2


a2 : Int -> Int -> String
a2 m n =
    if n > 0 then
        a1 (m - 1) (n - 1)

    else
        "done"


b1 : Int -> Int -> Int -> String
b1 =
    b2 1 2


b2 : Int -> Int -> Int -> Int -> Int -> String
b2 x1 x2 x3 x4 x5 =
    if True then
        "done"

    else
        b1 3 4 5

• Elm: lamdera/compiler @ 7bb3b2f

Additional Details

Found by @pithub here

I attempted to optimize these cases in #43 but got stuck on actually generating the needed JavaScript, making sure generated arg names don't collide with user-given ones, etc.

It should be technically possible to do this but it's not a 5-minute fix.

Until then we do what Gren did and just don't optimize cyclic function definitions in this way and fall back to AX/FX.

[MartinSStewart]

Thanks for looking into this! I don't really have much to add, reviewing Haskell isn't my strong suit 😅

Hopefully @supermario has time to review this.

[Janiczek]

With the test we're showing that the designated "beginning of the cycle" doesn't get called directly (there's no $b1$), but the other parts of the cycle do.

[supermario]

Thanks @Janiczek 👍