:doc command does not work on ghc boot libraries with ghc-8.6.4
In the GHC 8.6.4, GHCi's :doc
command does not work on ghc boot libraries, such as GHC.Base
.
Perhaps boot libraries of GHC 8.6.4 were compiled without the -haddock
option.
At least, it occurs in linux and windows binaries of GHC 8.6.4:
- https://downloads.haskell.org/~ghc/8.6.4/ghc-8.6.4-x86_64-deb9-linux.tar.xz
- https://downloads.haskell.org/~ghc/8.6.4/ghc-8.6.4-x86_64-unknown-mingw32.tar.xz
The error messages are as follows:
ghci> :doc id
ghc: Can't find any documentation for GHC.Base.
This is probably because the module was compiled without '-haddock',
but it's also possible that the module contains no documentation.
Try re-compiling with '-haddock'.
ghci> import Control.Monad.State
ghci> :doc State
ghc: Can't find any documentation for Control.Monad.Trans.State.Lazy.
This is probably because the module was compiled without '-haddock',
but it's also possible that the module contains no documentation.
Try re-compiling with '-haddock'.
Previous version of GHCi (ghc 8.6.3) could perform :doc
command as follows.
ghci> :doc id
Identity function.
> id x = x
ghci> import Control.Monad.State
ghci> :doc State
A state monad parameterized by the type @s@ of the state to carry.
The 'return' function leaves the state unchanged, while @>>=@ uses
the final state of the first computation as the initial state of
the second.