Documentation does not mention that default definitions for Alternative(some, many) can easily blow up

Consider this case (taken from #11649 (closed))

import Control.Applicative

data U1 p = U1

instance Functor U1 where
    fmap f U1 = U1

instance Applicative U1 where
    pure _ = U1
    U1 <*> U1 = U1

instance Alternative U1 where
    empty = U1
    U1 <|> U1 = U1

instance Show (U1 p) where
    show U1 = "U1"

main = print (some U1)

This looks fine, right? Wrong,

$ ./Main
Main: <<loop>>

Of course, this can be avoided by simply defining some and many in U1's Alternative instance,

instance Alternative U1 where
    empty = U1
    U1 <|> U1 = U1
    some U1 = U1
    many U1 = U1

It seems that the default definitions of some and many will produce looping code in these cases (although it's not entirely clear to me which cases "these" cases are).

I suppose this is due to the fact that U1 will always "succeed". We should note this in the documentation to ensure that users don't end up with accidentally bottoming instances.