Discussion on: Improving Elm's compiler output

monomorphising doesn't do inling. When a monomorphising compiler sees the following code:

listmap : (a -> b) -> List a -> List b
listmap fn list =
    List.foldl (\a acc -> fn a :: acc) list
    |> List.reverse

strs = listmap String.fromInt [ 1, 2, 3 ]

strs = listmap isEven [ 1, 2, 3 ]

it will generate two versions of listmap, one which has the type (Int -> String) -> List Int -> List String and one which has the type (Int -> Bool) -> List Int -> List Bool. It will then use the specialized listmap implementations where it can.

This allows the compiler to specialize code better, because it has precise type information.