#5445: programatica package compilation fails
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Reporter: maeder | Owner: simonpj
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.2.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: GHC rejects valid program
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Comment(by simonpj@…):
commit faadd61ef05e8f84a2ad7e0fb6b6d873a7b8c232
{{{
Author: Simon Peyton Jones <[email protected]>
Date: Fri Sep 2 09:20:45 2011 +0100
Two bugs in rnExports (fixes Trac #5445)
When constructing export lists, data families pose an awkward problem,
documented in Note [Exports of data families] in RnNames. Consider
module M where
import X( D )
data instance D Int = M1 | M2
Here M exports M1 and M2, obviously, but does it export D? It would
not usually do so, but if we don't then no one can import M
selectively
like this:
import M( D(M1,M2) )
So we compromise and export D too. But I made two mistakes
a) Didn't check for conflicts between the extra export of X.D
and any other exports called "D"
b) Did the extra export for imported things too, not just ones defined
in this module (ie made the compromise apply much more widely than
necessary)
This made Programatica (a complex project) break in an obscure
way; (b) caused an export conflict, (a) meant that the conflict
was not spotted, which in turn caused later chaos.
Anyway the fix is easy, and is documented in the Note.
compiler/rename/RnNames.lhs | 73
++++++++++++++++++++++++++----------------
1 files changed, 45 insertions(+), 28 deletions(-)
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5445#comment:2>
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