#5868: Wrong error messages with qualified imports
---------------------------------+------------------------------------------
Reporter: SimonHengel | Owner:
Type: bug | Status: new
Priority: normal | Milestone: _|_
Component: Compiler | Version: 7.4.1
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: None/Unknown
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Changes (by simonpj):
* difficulty: => Unknown
* milestone: => _|_
Comment:
Correct.
By the time we get to the type checker, GHC has forgotten ''how'' the
entity was referenced and has simply recorded ''what'' entity was
referenced. In this case it knows that you are talking about "the `bar`
defined in module `Bar`", but has forgotten what you called it. Then
when it prints the error message it tries to find some unambiguous name
for it; hence the result.
It isn't perfect I grant you. One way to improve matters might be to
change the `HsExpr` data type a bit, so instead of
{{{
data HsExpr id = HsVar id
| ...
}}}
we have
{{{
data HsExpr id = HsVar id RdrName
| ...
}}}
so that every `HsVar` remembers how it was originally specified. That
would catch 90% of the cases, but I worry about the others (eg qualified
use of data constructors in patterns). A more thorough solution might be
to make the renamer produce `HsExpr (Name, RdrName)` rather than `HsExpr
Name`. But it's also pretty expensive.
My gut feel is to let sleeping dogs lie unless more people pipe up that
this is really painful.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5868#comment:1>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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