#15393: Regression: Detection of unused imports is imprecise (since GHC 8.0.1)
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Reporter: SimonHengel | Owner: (none)
Type: bug | Status: closed
Priority: normal | Milestone: 8.6.1
Component: Compiler | Version: 8.4.1
Resolution: duplicate | 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):
Wiki Page: |
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Comment (by Ben Gamari ):
In [changeset:"6353efc7694ba8ec86c091918e02595662169ae2/ghc"
6353efc7/ghc]:
{{{
#!CommitTicketReference repository="ghc"
revision="6353efc7694ba8ec86c091918e02595662169ae2"
Fix unused-import warnings
This patch fixes a fairly long-standing bug (dating back to 2015) in
RdrName.bestImport, namely
commit 9376249b6b78610db055a10d05f6592d6bbbea2f
Author: Simon Peyton Jones
Date: Wed Oct 28 17:16:55 2015 +0000
Fix unused-import stuff in a better way
In that patch got the sense of the comparison back to front, and
thereby failed to implement the unused-import rules described in
Note [Choosing the best import declaration] in RdrName
This led to Trac #13064 and #15393
Fixing this bug revealed a bunch of unused imports in libraries;
the ones in the GHC repo are part of this commit.
The two important changes are
* Fix the bug in bestImport
* Modified the rules by adding (a) in
Note [Choosing the best import declaration] in RdrName
Reason: the previosu rules made Trac #5211 go bad again. And
the new rule (a) makes sense to me.
In unravalling this I also ended up doing a few other things
* Refactor RnNames.ImportDeclUsage to use a [GlobalRdrElt] for the
things that are used, rather than [AvailInfo]. This is simpler
and more direct.
* Rename greParentName to greParent_maybe, to follow GHC
naming conventions
* Delete dead code RdrName.greUsedRdrName
Bumps a few submodules.
Reviewers: hvr, goldfire, bgamari, simonmar, jrtc27
Subscribers: rwbarton, carter
Differential Revision: https://phabricator.haskell.org/D5312
}}}
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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15393#comment:8
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