#4806: Make error message more user friendly when module is not found because package is unusable -------------------------------------+------------------------------------- Reporter: mitar | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.0.1 Resolution: | Keywords: newcomer Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Phab:D4783 Wiki Page: | -------------------------------------+------------------------------------- Comment (by Ben Gamari ): In [changeset:"df0f148feae4c3b9653260edff843d561d6d5918/ghc" df0f148f/ghc]: {{{ #!CommitTicketReference repository="ghc" revision="df0f148feae4c3b9653260edff843d561d6d5918" Improve error message when importing an unusable package If a module cannot be found because it is ignored or from an unusable package, report this to the user and the reason it is unusable. Currently, GHC displays the standard "Cannot find module error". For example: ``` <no location info>: error: Could not find module ‘Control.Monad.Random’ Perhaps you meant Control.Monad.Reader (from mtl-2.2.2) Control.Monad.Cont (from mtl-2.2.2) Control.Monad.Error (from mtl-2.2.2) ``` GHC does, however, indicate unusable/ignored packages with the -v flag: ``` package MonadRandom-0.5.1-1421RgpXdhC8e8UI7D3emA is unusable due to missing dependencies: fail-4.9.0.0-BAHmj60kS5K7NVhhKpm9J5 ``` With this change, I took that message and added it to the output of the "Cannot find module" message. Reviewers: bgamari, dfeuer Reviewed By: bgamari Subscribers: Phyx, dfeuer, rwbarton, thomie, carter GHC Trac Issues: #4806 Differential Revision: https://phabricator.haskell.org/D4783 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/4806#comment:35 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler