#7672: boot file entities are sometimes invisible and are not (semantically)
unified with corresponding entities in implementing module
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Reporter: skilpat | Owner: ezyang
Type: bug | Status: new
Priority: normal | Milestone: 7.12.1
Component: Compiler (Type | Version: 7.4.2
checker) | Keywords: backpack
Resolution: | Architecture: x86_64
Operating System: Linux | (amd64)
Type of failure: GHC rejects | Test Case: T7672
valid program | Blocking: 10336
Blocked By: | Differential Revisions:
Related Tickets: |
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Comment (by Simon Peyton Jones ):
In [changeset:"9b73cb16485f331d9dc1f37826c6d503e24a5b0b/ghc"]:
{{{
#!CommitTicketReference repository="ghc"
revision="9b73cb16485f331d9dc1f37826c6d503e24a5b0b"
Refactor the GlobalRdrEnv, fixing #7672
This patch started innocently enough, by deleting a single
call from rnImportDecl, namely
let gbl_env = mkGlobalRdrEnv (filterOut from_this_mod gres)
The 'filterOut' makes no sense, and was the cause of #7672.
But that little loose end led to into a twisty maze of little
passages, all alike, which has taken me an unreasonably long
time to straighten out. Happily, I think the result is really
much better.
In particular:
* INVARIANT 1 of the GlobalRdrEnv type was simply not true:
we had multiple GlobalRdrElts in a list with the same
gre_name field. This kludgily implmented one form of
shadowing.
* Meanwhile, extendGlobalRdrEnvRn implemented a second form of
shadowing, by deleting stuff from the GlobalRdrEnv.
* In turn, much of this shadowing stuff depended on the Names of
the Ids bound in the GHCi InteractiveContext being Internal
names, even though the TyCons and suchlike all had External
Names. Very confusing.
So I have made the following changes
* I re-established INVARIANT 1 of GlobalRdrEnv. As a result
some strange code in RdrName.pickGREs goes away.
* RnNames.extendGlobalRdrEnvRn now makes one call to deal with
shadowing, where necessary, and another to extend the
environment. It deals separately with duplicate bindings.
The very complicated RdrName.extendGlobalRdrEnv becomes much
simpler; we need to export the shadowing function, now called
RdrName.shadowNames; and we can nuke
RdrName.findLocalDupsRdrEnv altogether.
RdrName Note [GlobalRdrEnv shadowing] summarises the shadowing
story
* The Names of the Ids bound in the GHCi interactive context are
now all External. See Note [Interactively-bound Ids in GHCi]
in HscTypes.
* Names for Ids created by the debugger are now made by
IfaceEnv.newInteractiveBinder. This fixes a lurking bug which
was that the debugger was using mkNewUniqueSupply 'I' to make
uniques, which does NOT guarantee a fresh supply of uniques on
successive calls.
* Note [Template Haskell ambiguity] in RnEnv shows that one TH-related
error is reported lazily (on occurrences) when it might be better
reported when extending the environment. In some (but not all) cases
this was done before; but now it's uniformly at occurrences. In
some ways it'd be better to report when extending the environment,
but it's a tiresome test and the error is rare, so I'm leaving it
at the lookup site for now, with the above Note.
* A small thing: RnNames.greAvail becomes RdrName.availFromGRE, where
it joins the dual RdrName.gresFromAvail.
}}}
--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/7672#comment:15
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