有没有办法向GHCI询问特定实例的定义位置？

Question

例如,我可以查询"RWS定义为MonadState实例的位置"吗？我期待一个像模块(版本),源文件,行的答案.

Answer 1

?> :info MonadState
...
instance (Monad m, Monoid w) => MonadState s (RWST r w s m)
  -- Defined in `Control.Monad.State.Class'
?> :i RWS
type RWS r w s = RWST r w s Identity
        -- Defined in `Control.Monad.Trans.RWS.Lazy'
?> :i RWST
...
instance MonadState s m => MonadState s (Reader.ReaderT r m)
  -- Defined in `Control.Monad.State.Class'
...

您无法获取行信息,它只显示当前加载的模块,但这足以捕获实例.