#9780: dep_orphs in Dependencies redundantly records type family orphans
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Reporter: ezyang | Owner:
Type: bug | Status: closed
Priority: normal | Milestone: 7.10.1
Component: Compiler | Version: 7.9
Resolution: fixed | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: Compile-time | Unknown/Multiple
performance bug | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Revisions:
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Changes (by thomie):
* status: new => closed
* resolution: => fixed
* milestone: => 7.10.1
Comment:
You updated that comment in commit
4c834fdddf4d44d12039da4d6a2c63a660975b95:
{{{
Author: Edward Z. Yang <>
Date: Mon Nov 17 21:23:52 2014 -0800
Filter instance visibility based on set of visible orphans, fixes
#2182.
Summary:
Amazingly, the fix for this very old bug is quite simple: when type-
checking,
maintain a set of "visible orphan modules" based on the orphans list
of
modules which we explicitly imported. When we import an instance and
it
is an orphan, we check if it is in the visible modules set, and if
not,
ignore it. A little bit of refactoring for when orphan-hood is
calculated
happens so that we always know if an instance is an orphan or not.
For GHCi, we preinitialize the visible modules set based on the list
of
interactive imports which are active.
Future work: Cache the visible orphan modules set for GHCi, rather
than
recomputing it every type-checking round. (But it's tricky what to do
when you
/remove/ a module: you need a data structure a little more complicated
than
just a set of modules.)
Signed-off-by: Edward Z. Yang