#13064: Incorrect redudant imports warning -------------------------------------+------------------------------------- Reporter: phadej | Owner: davide Type: bug | Status: closed Priority: high | Milestone: 8.8.1 Component: Compiler | Version: 8.0.1 Resolution: fixed | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Incorrect | Unknown/Multiple error/warning at compile-time | Test Case: Blocked By: | Blocking: Related Tickets: #15393 | Differential Rev(s): Phab:D5312 Wiki Page: | -------------------------------------+------------------------------------- Changes (by davide): * status: new => closed * resolution: => fixed Old description:
With a simple package:
issue.cabal: {{{ name: issue version: 0 cabal-version: >= 1.10 build-type: Simple
library build-depends: base, binary, binary-orphans==0.1.5.2 exposed-modules: Issue }}}
Issue.hs: {{{ {-# LANGUAGE DeriveGeneric #-} {-# OPTIONS_GHC -Wall #-} module Issue (T (..)) where
import Prelude () import Data.Binary.Orphans import Data.Binary (Binary (..)) import GHC.Generics (Generic) import Data.Aeson (Value)
data T = T Value deriving (Generic)
instance Binary T }}}
GHC 7.10.3 correctly reports: {{{ Issue.hs:7:1: Warning: The import of ‘Data.Binary’ is redundant except perhaps to import instances from ‘Data.Binary’ To import instances alone, use: import Data.Binary() }}}
GHC 8.0.1 incorrectly (!!!) reports:
{{{ Issue.hs:6:1: warning: [-Wunused-imports] The import of ‘Data.Binary.Orphans’ is redundant except perhaps to import instances from ‘Data.Binary.Orphans’ To import instances alone, use: import Data.Binary.Orphans( }}}
but `Binary Value` instance is imported from `Data.Binary.Orphans`.
---
In real life while compiling https://github.com/futurice/haskell-mega- repo/blob/93c3f111f39c973769c35725d90c9b8ef9a57de3/futurice- github/src/Futurice/GitHub.hs the `Data.Binary` redundant import isn't reported, as `Futurice.Prelude` exports other stuff, which is used. See https://gist.github.com/phadej/bb26df19c611260ab8f867729def39b9 for minimal imports reported with `-ddump-minimal-imports`.
## Status
I've submitted some PRs to fix the impending unused import warnings:
* MERGED https://github.com/haskell/cabal/pull/5673 * https://github.com/kolmodin/binary/pull/159 * MERGED https://github.com/haskell/bytestring/pull/168 * MERGED https://github.com/haskell/containers/pull/576 * MERGED https://github.com/haskell/text/pull/240
I've also added a new ghc patch here: * https://phabricator.haskell.org/D5312
New description: With a simple package: issue.cabal: {{{ name: issue version: 0 cabal-version: >= 1.10 build-type: Simple library build-depends: base, binary, binary-orphans==0.1.5.2 exposed-modules: Issue }}} Issue.hs: {{{ {-# LANGUAGE DeriveGeneric #-} {-# OPTIONS_GHC -Wall #-} module Issue (T (..)) where import Prelude () import Data.Binary.Orphans import Data.Binary (Binary (..)) import GHC.Generics (Generic) import Data.Aeson (Value) data T = T Value deriving (Generic) instance Binary T }}} GHC 7.10.3 correctly reports: {{{ Issue.hs:7:1: Warning: The import of ‘Data.Binary’ is redundant except perhaps to import instances from ‘Data.Binary’ To import instances alone, use: import Data.Binary() }}} GHC 8.0.1 incorrectly (!!!) reports: {{{ Issue.hs:6:1: warning: [-Wunused-imports] The import of ‘Data.Binary.Orphans’ is redundant except perhaps to import instances from ‘Data.Binary.Orphans’ To import instances alone, use: import Data.Binary.Orphans( }}} but `Binary Value` instance is imported from `Data.Binary.Orphans`. --- In real life while compiling https://github.com/futurice/haskell-mega- repo/blob/93c3f111f39c973769c35725d90c9b8ef9a57de3/futurice- github/src/Futurice/GitHub.hs the `Data.Binary` redundant import isn't reported, as `Futurice.Prelude` exports other stuff, which is used. See https://gist.github.com/phadej/bb26df19c611260ab8f867729def39b9 for minimal imports reported with `-ddump-minimal-imports`. ## Status I've submitted some PRs to fix the impending unused import warnings: * MERGED https://github.com/haskell/cabal/pull/5673 * MERGED https://github.com/kolmodin/binary/pull/159 * MERGED https://github.com/haskell/bytestring/pull/168 * MERGED https://github.com/haskell/containers/pull/576 * MERGED https://github.com/haskell/text/pull/240 I've also added a new ghc patch here: * MERGED https://phabricator.haskell.org/D5312 -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13064#comment:51 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler