GHC-8.0.2+ spits out $dm names in error messages
Example (copied from #12881 (closed))
{-# LANGUAGE FlexibleInstances #-}
module Bug where
class Arbitrary a where
shrink :: a -> [a]
shrink _ = []
instance Arbitrary a
instance Arbitrary Int
Error message is:
GHCInstance.hs:10:10: error:
T13755.hs:9:10: error:
• Overlapping instances for Arbitrary Int
arising from a use of ‘Bug.$dmshrink’
Matching instances:
instance Arbitrary a -- Defined at T13755.hs:8:10
instance Arbitrary Int -- Defined at T13755.hs:9:10
• In the expression: Bug.$dmshrink @Int
In an equation for ‘shrink’: shrink = Bug.$dmshrink @Int
In the instance declaration for ‘Arbitrary Int’
Another example: code in #13754 (closed) description.