Wrong suggestion when deriving Generic on an instantiated type
The following code
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE FlexibleInstances #-}
import GHC.Generics
data A a
data B
deriving instance Generic (A B)
gives rise to the error
Can't make a derived instance of `Generic (A B)':
A must not be instantiated; try deriving `A B' instead
In the stand-alone deriving instance for `Generic (A B)'
It should indeed fail, but the suggestion should be to try deriving A a
instead.
Trac metadata
Trac field | Value |
---|---|
Version | 7.6.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |