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Suppose (see #17752 (closed)) we have a recursive function with a RULE

elem :: Eq a => a -> [a] -> [a]
{-# NOINLNE[1] elem #-}
elem = ...elem...

{-# RULES
"elem/build"    forall x (g :: forall b . (a -> b -> b) -> b -> b)
   . elem x (build g) = g (\ y r -> (x == y) || r) False
 #-}

The NOINLINE pragma is there to ensure elem doesn't inline before the RULE has had a chance to fire.

But after it's had its chance to fire (and failed to do so) we may well want to specialise elem. Since it is recursive we'd usually write

{-# INLINABLE  elem #-}  

But GHC doesn't allow that:

test.hs:24:15: error:
    Duplicate INLINABLE pragmas for `elem'
-}

We should make it possible to have both a NOLININE[n] pragma and an INLINABLE pragma. There's no contradiction!

We might want to warn about NOLININE vs INLINABLE since it's silly to keep the unfolding for a function that cannot, ever, be inlined.

We'd need to take care that specialisation rules don't fire if we in an NOINLNE phase.