Invalid example in ScopedTypeVariables documentation
Summary
In GHC user's guide, the last section of the ScopedTypeVariables
explanation contains this example:
class D a where
m :: [a] -> a
instance D [a] where
m :: [a] -> [a]
m = reverse
The preceding text claims that "the example will be accepted without explicitly enabling ScopedTypeVariables
" but in fact the example can't compile with any combination of extensions.
Proposed improvements or changes
This instance would compile and fit in the context:
instance D [a] where
m :: [[a]] -> [a]
m = concat