% ghc --version; cabal --version; haddock --version; cabal haddock
The Glorious Glasgow Haskell Compilation System, version 8.0.1
cabal-install version 2.2.0.0
compiled using version 2.2.0.0 of the Cabal library
Haddock version 2.17.4, (c) Simon Marlow 2006
Ported to use the GHC API by David Waern 2006-2008
Preprocessing library for opaleye-0.6.1.0..
Running Haddock on library for opaleye-0.6.1.0..
Warning: The documentation for the following packages are not installed. No
links will be generated to these packages: StateVar-1.1.0.4, ...
<no location info>: error:
module ‘opaleye-0.6.1.0-54np2PrjcDbJYVV9W7uGXD:Main’ is defined in multiple files: src/Opaleye/Operators.hs
src/Opaleye/Order.hs
这似乎不是cabal haddock failing because function is defined in multiple files的一个实例，因为我不在Mac上且cabal haddock --ghc-options=-optP-P不起作用。