The most common legitimate usage for undefined I have is strictness:

func x y | x `seq` False = undefined
func x y = ...

There's nothing else that would go there, and when it's compiled, the reference to undefined disappears.

On Sun, Dec 22, 2019, 05:50 chessai . <chessai1996@gmail.com> wrote:
Right, it's been discussed before IIRC, and i know I've certainly given it passing thoughts. I think this isn't worth it because of breakage. Many people use -Wall -Werror, so I see this as a no-go.

Thanka

On Sun, Dec 22, 2019, 6:45 AM Vilem Liepelt <vliepelt@futurefinance.com> wrote:
Has there been any discussion about adding WARNING pragmas to `Prelude.undefined` and `Prelude.error`, as done in some custom preludes?

I suppose this hasn't been done yet to avoid breaking existing code which makes "legitimate" use of those helpers?
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