#13214: Orphan instances in Backpack signatures don't work
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Reporter: ezyang | Owner: ezyang
Type: bug | Status: patch
Priority: normal | Milestone: 8.2.1
Component: Compiler (Type | Version: 8.1
checker) |
Resolution: | Keywords: backpack
Operating System: Unknown/Multiple | Architecture:
| Unknown/Multiple
Type of failure: None/Unknown | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): Phab:D3095
Wiki Page: |
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Comment (by Ben Gamari ):
In [changeset:"26eaa7ecde288b9dc123f3c120e70b2cf18b4e4a/ghc"
26eaa7ec/ghc]:
{{{
#!CommitTicketReference repository="ghc"
revision="26eaa7ecde288b9dc123f3c120e70b2cf18b4e4a"
Fix #13214 by correctly setting up dep_orphs for signatures.
Prior to this, I hadn't thought about orphan handling at all.
This commit implements the semantics that if a signature
(transitively) imports an orphan instance, that instance
is considered in scope no matter what the implementing module
is. (As it turns out, this is the semantics that falls out
when orphans are recorded transitively.)
This patch fixes a few bugs:
1. Put semantic modules in dep_orphs rather than identity
modules.
2. Don't put the implementing module in dep_orphs when
merging signatures (this is a silly bug that happened
because we were reusing calculateAvails, which is
designed for imports. It mostly works for signature
merging, except this case.)
3. When renaming a signature, blast in the orphans of the
implementing module inside Dependencies.
Signed-off-by: Edward Z. Yang
Test Plan: validate
Reviewers: bgamari, austin
Reviewed By: bgamari
Subscribers: thomie
Differential Revision: https://phabricator.haskell.org/D3095
}}}
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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13214#comment:2
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