Documentation for Ix is contradictory around minimal definition

The Haddock documentation for Ix here says that the minimal definition requires range, index, and inRange. But then it says that the minimal definition requires range and inRange. It seems that Haddock is inferring a MINIMAL definition where none is in the code. Perhaps a MINIMAL should be added.

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Core Libraries
Test case
Differential revisions
BlockedBy
Related
Blocking
CC	core-libraries-committee@haskell.org
Operating system
Architecture

changed weight to 5

added Tbug Trac import core libraries labels

assigned to @hvr and unassigned @trac-ekmett

so while range and inRange have no default implementation, index has one that is recursive:

        -- Must specify one of index, unsafeIndex

        -- 'index' is typically over-ridden in instances, with essentially
        -- the same code, but using indexError instead of hopelessIndexError
        -- Reason: we have 'Show' at the instances
    {-# INLINE index #-}  -- See Note [Inlining index]
    index b i | inRange b i = unsafeIndex b i
              | otherwise   = hopelessIndexError

    unsafeIndex b i = index b i

So the minimal pragma should specify that we minimally need

range && inRange && (index || unsafeIndex)

I'll make a patch rightaway...

Trac metadata

Trac field	Value
Differential revisions	→ D709

changed milestone to %7.10.1

mentioned in commit 7a2d65a4

closed

landed to ghc-7.10 via 0d586136

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

added Pnormal label