ImplicitParams does not imply FlexibleContexts or FlexibleInstances

Given:

{-# LANGUAGE ImplicitParams       #-}
{-# LANGUAGE FlexibleInstances    #-}

module Test where

data X a = X
type XI = X Int

class Foo a where
  foo :: (?p :: Int) => a -> Int

instance Foo XI where foo = undefined

This code compiles. However, the documentation at https://downloads.haskell.org/~ghc/master/users-guide/glasgow_exts.html#language-options says that ImplicitParams implies FlexibleInstances, so we should be able to remove the FlexibleInstances extension. However, doing so makes it stop compiling.

My guess is that ImplicitParams doesn't really imply either of the type class extensions, and that the documentation is buggy.

Trac metadata

Trac field	Value
Version	8.6.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Documentation
Test case
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CC	ndmitchell@gmail.com
Operating system
Architecture