#13214: Orphan instances in Backpack signatures don't work -------------------------------------+------------------------------------- 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: | -------------------------------------+------------------------------------- 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 }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13214#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler