WARNING pragmas in `Prelude.undefined` and `Prelude.error`

[Vilem Liepelt]

> On 22 Dec 2019, at 14:15, Zemyla <zemyla at gmail.com> wrote:
> 
> 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.

Is this (better than | different from) using BangPatterns?