Type checking bug

[jmackie]

module Wut exports (..)


type Result(a, e) =
    | Ok(a)
    | Err(e)

map_result = fn (result: Result(a, e), f: (a) -> b): Result(b, e) ->
    match result with
    | Ok(a) -> Ok(f(a))
    | Err(err) -> Err(err)
    end

type Decoder(input, output) = Decoder((input) -> Result(output, Unit))

type alias StringDecoder(output) = Decoder(String, output)

-- This does two strange things:
--   * an incorrect type error
--   * warns about a redundant match pattern (maybe the root cause)
-- Both of which go away when you don't use the `StringDecoder` alias...
huh = fn (Decoder(decode): StringDecoder(a)): StringDecoder(Array(a)) ->
    Decoder(fn (s) -> map_result(decode(s), fn (a) -> [a]))

wut = fn (Decoder(decode): Decoder(String, a)): Decoder(String, Array(a)) ->
    Decoder(fn (s) -> map_result(decode(s), fn (a) -> [a]))

:scratches-head: