Proposal to deprecate and then drop fromJust

Oleg Grenrus oleg.grenrus at
Tue Feb 24 10:28:01 UTC 2015

> On 24 Feb 2015, at 12:23, Erik de Castro Lopo <mle+hs at> wrote:
> Possibly what we need is a pragma to mark functions partial and a warning
> flag that warns on usage of functions that have been marked partial.

I had this in mind too, but that is very heavy solution. I’d rather start with making hlint warnings?

foo :: Maybe Int -> Int
foo x = if isJust x then fromJust x else 0

bar :: Maybe Int -> Int
bar x = 1 + fromJust x

It warns about `foo` nonsense. It could propose to change `bar` part into `fromMaybe (error “I’know what I’m doing”) x`  ?

- Oleg

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