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Edward Z. Yang authored
Summary: For holes, its necessary to "see through" the instantiation of the hole to get accurate family instance dependencies. For example, if B imports <A>, and <A> is instantiated with F, we must grab and include all of the dep_finsts from F to have an accurate transitive dep_finsts list. However, we MUST NOT do this for regular modules. First, for efficiency reasons, doing this bloats the the dep_finsts list, because we *already* had those modules in the list (it wasn't a hole module, after all). But there's a second, more important correctness consideration: we perform module renaming when running --abi-hash. In this case, GHC's contract to the user is that it will NOT go and read out interfaces of any dependencies (https://github.com/haskell/cabal/issues/3633); the point of --abi-hash is just to get a hash of the on-disk interfaces for this *specific* package. If we go off and tug on the interface for /everything/ in dep_finsts, we're gonna have a bad time. (It's safe to do do this for hole modules, though, because the hmap for --abi-hash is always trivial, so the interface we request is local. Though, maybe we ought not to do it in this case either...) Signed-off-by: Edward Z. Yang <ezyang@fb.com> Test Plan: validate Reviewers: alexbiehl, goldfire, bgamari Subscribers: ppk, shlevy, rwbarton, carter GHC Trac Issues: #15594 Differential Revision: https://phabricator.haskell.org/D5123
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